Shapeshifting catalysts and methods of preparation and use thereof

Abstract

A shapeshifting catalyst is provided that includes a ligand with an aromatic N-heterocycle and an alkenyl group and a transition metal cation, wherein under a charge-localized state, the ligand coordinates to the transition metal cation in a bidentate mode, under a charge-separated state, the ligand coordinates to the transition metal cation in a monodentate mode, and the charge-localized state and the charge-separated state interconvert to each other through formation or dissociation of a C–N bond. Also provided are methods of preparing and using the catalyst and an article of manufacture including the catalyst.

Description

Attorney Docket No. 0073605-001022 SHAPESHIFTING CATALYSTS AND METHODS OF PREPARATION AND USE THEREOF CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Application Serial No.63 / 668,479, filed on July 8, 2024, and entitled “SHAPESHIFTING COMPOUNDS FOR POLYETHYLENE / POLAR MONOMER COPOLYMERS”, the entirety of which is incorporated herein by reference. FIELD OF THE INVENTION

[0002] The present invention generally relates to the field of catalysis. In particular, the presentinvention is directed to shapeshifting catalysts and methods of preparation and use thereof. BACKGROUND

[0003] Lewis acidic catalysts have proven enormously useful for the polymerization of styrene,ethylene, propylene, and other nonpolar olefinic monomers. These catalysts have made the plastic revolution possible, and the products produced using these catalysts are now inescapable. The properties for Lewis acidic transition metal complexes make them useful for activating olefinic substrates. However, when used as catalysts, those same properties predispose these compounds to inhibition and / or death (e.g., through irreversible substrate coordination). Most supporting ligands are Lewis bases, and so their association intrinsically tempers Lewis acidity. SUMMARY OF THE DISCLOSURE

[0004] Derivative plastics made by including a small percentage of a functionalized monomercan retain the useful mechanical properties of the parent polymer. Inclusion of these additional monomers also results in new functions for the derivative plastics. However, these functionalized monomers tend to be more Lewis basic than an olefin and are incompatible with current-generation catalysts. Catalysts that are both highly active for olefin polymerization and generally tolerant of Lewis bases have proven elusive.

[0005] An aspect of the present disclosure is a shapeshifting catalyst. Specifically, throughligand design, the present disclosure provides a shapeshifting catalyst that has access to two states. These two states are electronic dissimilar to one another – e.g., one state being highly Lewis acidic and the other being more Lewis basic. These two-state, shapeshifting catalysts showed superior performance compared to traditional catalysts based on static ligands. More specifically, these shapeshifting catalysts are generally tolerant of Lewis basic functionality but retain activity that isAttorney Docket No. 0073605-001022 intrinsic to Lewis acidic catalysts. Detailed mechanisms describing the working principles of the shapeshifting catalyst are provided in FIGS. 1A-F.

[0006] In some embodiments, the shapeshifting catalyst can have a charge-localized state inchemical equilibrium with a charge-separated state. The shapeshifting catalyst can include a ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker, such as without limitation an alkylene linker having a length of two to five C atoms. The shapeshifting catalyst can further include a transition metal cation, wherein under the charge-localized state, the ligand coordinates to the transition metal cation in a bidentate mode through an N atom of the aromatic N-heterocycle and the alkenyl group, and under the charge-separated state, the ligand coordinates to the transition metal cation in a monodentate mode. The charge-localized state and the charge-separated state can interconvert to each other through formation or dissociation of a C–N bond.

[0007] In some embodiments, the shapeshifting catalyst can have an electrophilic state inchemical equilibrium with a nucleophilic state. The shapeshifting catalyst can include a ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker, such as without limitation an alkylene linker having a length of two to five C atoms. The shapeshifting catalyst can further include a transition metal cation, wherein under the electrophilic state, the ligand coordinates to the transition metal cation in a bidentate mode through an N atom of the aromatic N-heterocycle and the alkenyl group, and under the nucleophilic state, the ligand coordinates to the transition metal cation in a monodentate mode. The electrophilic state and the nucleophilic state can interconvert to each other through formation or dissociation of a C–N bond.

[0008] In some embodiments, the shapeshifting catalyst can have an unmasked Lewis acidicstate in chemical equilibrium with a masked Lewis acidic state. The shapeshifting catalyst can include a ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker, such as without limitation an alkylene linker having a length of two to five C atoms. The shapeshifting catalyst can further include a transition metal cation, wherein under the unmasked Lewis acidic state, the ligand coordinates to the transition metal cation in a bidentate mode through an N atom of the aromatic N-heterocycle and the alkenyl group, and under the masked Lewis acidic state, the ligand coordinates to the transitionAttorney Docket No. 0073605-001022 metal cation in a monodentate mode. The unmasked Lewis acidic state and the masked Lewis acidic state can interconvert to each other through formation or dissociation of a C–N bond.

[0009] In some embodiments, the transition metal cation can be a cation of a metal elementfrom Group 4, 6, 9, 10, or 11 of the periodic table. In some embodiments, the transition metal cation can be a cation of Pd or Pt. In some embodiments, the transition metal cation can be a divalent or multivalent cation. In some embodiments, the transition metal cation can be Pd(II).

[0010] In some embodiments, the formation or dissociation of the C–N bond can beaccompanied by a cyclization or retrocyclization of a five- six, seven-, or eight-membered ring.

[0011] In some embodiments. the aromatic N-heterocycle can include one or more N-heterocycles selected from a group consisting of a substituted or unsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstituted oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substituted or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted or unsubstituted tetrazine, a substituted or unsubstituted purine, and a substituted or unsubstituted pteridine, wherein the one or more N-heterocycles can be optionally fused with a substituted or unsubstituted benzene, furan, pyrrole, thiophene, indole, naphthalene, anthracene, phenathrene, chryscene, or pyrene.Attorney Docket No. 0073605-001022

[0012] In some embodiments. the aromatic N-heterocycle can include a substituted orunsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstituted oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substituted or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted or unsubstituted tetrazine, a substituted or unsubstituted purine, and / or a substituted or unsubstituted pteridine, wherein the one or more N-heterocycles can be optionally fused with a substituted or unsubstituted benzene, furan, pyrrole, thiophene, indole, naphthalene, anthracene, phenathrene, chryscene, or pyrene.

[0013] In some embodiments, the aromatic N-heterocycle can include a condensed N-heterocycle of two or more members selected from a group consisting of a substituted or unsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstituted oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substitutedAttorney Docket No. 0073605-001022 or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted or unsubstituted tetrazine, a substituted or unsubstituted purine, and a substituted or unsubstituted pteridine.

[0014] In some embodiments, the aromatic N-heterocycle can include a condensed N-heterocycle of a substituted or unsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstituted oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substituted or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted or unsubstituted tetrazine, a substituted or unsubstituted purine, and / or a substituted or unsubstituted pteridine.Attorney Docket No. 0073605-001022

[0015] In some embodiments, the aromatic N-heterocycle can include a 14- or 18-electron πsystem.

[0016] In some embodiments, one or more H atoms of the alkylene linker can each besubstituted by a halogen atom, a straight-chain alkyl group having 1-12 C atoms, a branched or cyclic alkyl group having 3-12 C atoms, an alkenyl or alkynyl group having 2-12 C atoms, or an aryl group having 6-12 C atoms. In some embodiments, one or more H atoms of the alkylene linker can each be substituted by a methyl group.

[0017] In some embodiments, one or more H atoms of the alkenyl group can be substituted by ahalogen atom, a straight-chain alkyl group having 1-12 C atoms, a branched or cyclic alkyl group having 3-12 C atoms, an alkenyl or alkynyl group having 2-12 C atoms, or an aryl group having 6-12 C atoms. In some embodiments, one or more H atoms of the alkenyl group can be substituted by a - C6H4-C(CH3)3group.

[0018] In some embodiments, the shapeshifting catalyst can further include one or more labileligands coordinated to the transition metal cation. In some embodiments, at least one labile ligand of the one or more labile ligands can be an acetonitrile molecule.

[0019] In some embodiments, the shapeshifting catalyst can be a tetrafluoroborate (BF4-) salt, ahexafluoroborate (PF6-) salt, a trifluoromethanesulfonate or triflate (CF3SO3-) salt, or a tetrakis(3,5- bis(trifluoromethyl)phenyl)borate ([{3,5-(CF3)2C6H3}4B]-) salt of a cationic (i.e., positively charged) coordination complex. The cationic coordination complex can be produced by the ligand, the transition metal cation, and optionally one or more labile ligands.

[0020] In some embodiments, the transition metal cation can have a coordination number offour or six. Accordingly, in some embodiments, the transition metal cation can have a square planar or octahedral coordination geometry.

[0021] In some embodiments, the charge-separated, nucleophilic, or masked Lewis acidic statecan have a comparable stability to that of the respective charge-localized, electrophilic, or unmasked Lewis acidic state. In some embodiments, the charge-separated, nucleophilic, or masked Lewis acidic state can be thermodynamically more stable (i.e., associated with a lower or more negative Gibbs free energy) than the respective charge-localized, electrophilic, or unmasked Lewis acidic state. In some embodiments, the charge-separated, nucleophilic, or masked Lewis acidic can be thermodynamically uphill or downhill (e.g., in terms of Gibbs free energy) with respect to its corresponding charge-localized, electrophilic, or unmasked Lewis acidic, e.g., by any numericalAttorney Docket No. 0073605-001022 value deemed suitable or relevant according to a person of ordinary skill in the art, upon reviewing the entirety of this disclosure. In some embodiments, the charge-separated, nucleophilic, or masked Lewis acidic state has a Gibbs free energy that is lower than that of the respective charge-localized, electrophilic, or unmasked Lewis acidic state by no more than 30 kcal mol-1.

[0022] In some embodiments, both the charge-localized state and the charge-separated state canbe catalytically active. In some embodiments, only the charge-localized state can be catalytically active.

[0023] Another aspect of the present disclosure is a method of preparing the shapeshiftingcatalyst. The method includes metalating the ligand using a salt or coordination complex of the transition metal cation. In some embodiments, a coordination complex with one or more labile ligands, such as without limitation [Pd(MeCN)4][BF4]2, can be used as a starting material for preparing the shapeshifting catalyst.

[0024] Another aspect of the present disclosure is a method of using the shapeshifting catalystdescribed herein. The method includes providing a catalytically active amount of the shapeshifting catalyst to one or more organic substrates and transforming the one or more organic substrates into one or more products.

[0025] In some embodiments, the one or more organic substrates can be unsaturated and / orcontain one or more C=C bonds. In some embodiments, at least one organic substrate of the one or more organic substrates can be an unsubstituted or substituted olefin or styrene.

[0026] In some embodiments, at least one organic substrate or the one or more substrates caninclude a polar functional group. In some embodiments, the polar functional group can be selected from a list consisting of an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester, a sulfonate ester, a sulfonate ion, a halogen, and a pyridinyl group. In some embodiments, the polar functional group can include an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester group, sulfonate ester, a sulfonate ion, a halogen, and / or a pyridinyl group.

[0027] In some embodiments, the method can further include exposing the one or more organicsubstrates to the shapeshifting catalyst to facilitate a polymerization reaction, thereby producing a polymeric product. In some embodiments, the polymeric product can include polystyrene, polyethylene, or polypropylene. In some embodiments, the polymeric product can include a copolymer. In some embodiments, at least one monomer of the copolymer can include a polarAttorney Docket No. 0073605-001022 functional group. In some embodiments, the charge-separated, nucleophilic, or masked Lewis acidic state can be tolerant of polar functional groups. In some embodiments, both the charge-localized, nucleophilic, or masked Lewis acidic state and the charge-separated, electrophilic, or unmasked Lewis acidic state can be tolerant of polar functional groups.

[0028] Another aspect of the present disclosure is the use of the shapeshifting catalyst describedherein. In some embodiments, the shapeshifting catalyst can be used for an isomerization, oligomerization, telomerization, and / or polymerization or copolymerization reaction.

[0029] The shapeshifting catalysts (and catalyst design principles) described herein can beapplied to useful polymerization or copolymerization reactions. Specifically, these catalysts can be used to predictably generate organic materials with tunable properties and diffuse increasingly challenging synthetic problems. As nonlimiting examples, the catalysts disclosed herein can be used for styrene polymerization, ethylene polymerization, and / or the like. In addition, prevention of Lewis base inhibition, as disclosed herein, are compatible with the design principles generated from current best-of-class catalysts. The shapeshifting catalysts described herein have at least been successfully applied towards the copolymerization of styrene and polar styrene-like monomers; the tolerance of Lewis bases has proven transferable. Therefore, the present disclosure provides a solution that is generalizable to many Lewis basic monomers.

[0030] Another aspect of the present disclosure is an article of manufacture including theshapeshifting catalyst described herein.

[0031] Another aspect of the present disclosure is a method of stabilizing a Lewis-acidiccatalyst. The method includes coordinating a ligand to a transition metal cation of a Lewis-acidic catalyst, the ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker having a length of two to five C atoms, wherein under the charge-localized state, the ligand coordinates to the transition metal cation in a bidentate mode through an N atom of the aromatic N-heterocycle and the alkenyl group, under the charge-separated state, the ligand coordinates to the transition metal cation in a monodentate mode, and the charge-localized state and the charge-separated state interconvert to each other through formation or dissociation of a C–N bond.

[0032] Another aspect of the present disclosure is a method of making a polymeric material.The method includes providing a catalytically active amount of a shapeshifting catalyst. The shapeshifting catalyst includes a ligand having i) an aromatic N-heterocycle and ii) an alkenyl groupAttorney Docket No. 0073605-001022 covalently connected to the aromatic N-heterocycle through an alkylene linker having a length of two to five C atoms and a transition metal cation, wherein, under a charge-localized state, the ligand coordinates to the transition metal cation in a bidentate mode through one or more N atoms of the aromatic N-heterocycle and the alkenyl group, under a charge-separated state, the ligand coordinates to the transition metal cation in a monodentate mode, and the charge-localized state and the charge- separated state interconvert to one another through formation or dissociation of a C–N bond. The method further includes contacting the shapeshifting catalyst with one or more organic substrates to produce a polymeric product.

[0033] In some embodiments, the polymeric product can include polystyrene, polyethylene, orpolypropylene. In some embodiments, the polymeric product can include a copolymer. In some embodiments, at least one monomer of the copolymer can include a polar functional group.

[0034] In some embodiments, the charge-separated state can be tolerant of polar functionalgroups. In some embodiments, both the charge-localized state and the charge-separated state can be tolerant of polar functional groups. In some embodiments, the polar functional group can be selected from a list consisting of an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester, a sulfonate ester, a sulfonate ion, a halogen, and a pyridinyl group. In some embodiments, the polar functional group can include an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester group, a sulfonate ester, a sulfonate ion, a halogen, and / or a pyridinyl group. In some embodiments, the one or more organic substrates can be unsaturated. In some embodiments, at least one organic substrate of the one or more organic substrates can include an unsubstituted or substituted olefin or styrene.

[0035] These and other aspects and features of nonlimiting embodiments of the presentinvention will become apparent to those skilled in the art upon review of the following description of specific nonlimiting embodiments of the invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] For the purpose of illustrating the invention, the drawings show aspects of one or moreembodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings.Attorney Docket No. 0073605-001022

[0037] FIGS. 1A-F depict various schematics illustrating the mechanism of shapeshiftingcatalysis and ligation effects on their Lewis acidity, as described herein, and how shapeshifting catalysts differ from traditional catalysts using static ligands.

[0038] FIG. 2 depicts thermal ellipsoid plots of (a) [1][BF4]2, (b) [2][BF4]2 (counterionsomitted), (c) 3, and (d) L2; all presented at the 50% probability level. Hydrogen atoms and co- crystallized solvent molecules are omitted.

[0039] FIG. 3 depicts exemplary solid-phase attenuated total reflectance infrared (ATR-IR)spectra of [1][BF4]2, L1, and 3. Spectra have been baseline corrected and normalized in the νCHregion.

[0040] FIG. 4 depicts exemplary 2D exchange spectroscopy (2D-EXSY) data of a mixture ofL1 / [1]2+. Cross peaks indicate an exchange. (500 MHz, CD3CN)

[0041] FIG. 5 depicts exemplary solution-phase IR spectra of [1–PPh3]2+ and [2–PPh3]2+ inCD3CN. Spectra have been baseline corrected and normalized in the νCHregion.

[0042] FIG. 6 depicts time course data (collected by 1H NMR) for the isomerization of 1-hexeneto 2-hexene using Pd complexes. Observed νCNbands for those complexes are listed in the legend. Conditions: [Pd] = 1.1 mM (1.1 mol%), [1-hexene] = 96 mM, CD3CN, rt.

[0043] FIG. 7 depicts time course data (collected by 1H NMR) for the isomerization of cis-stilbene to trans-stilbene using Pd complexes. Conditions: [Pd] = 2.7 mM (8.0 mol%), [cis-stilbene] = 29 mM, CD3CN, rt.

[0044] FIG. 8A depicts a schematic representation of a consensus mechanism for isomerizationof cis-stilbene to trans-stilbene.

[0045] FIG. 8B depicts a schematic representation of the shapeshifting catalytic mechanismdescribed in the present disclosure.

[0046] FIG. 9 depicts exemplary time course data (collected by 1H NMR) for the isomerizationof hex-5-ene-2-one using various Pd complexes. Conditions: [Pd] = 1.4 mM (1.9 mol%), [hex-5-ene- 2-one] = 72 mM, CD3CN, rt.

[0047] FIG. 10 depicts data describing the isomerization of varying equivalents of hex-5-ene-2-one by Pd complexes. Conditions: [hex-5-ene-2-one] = 4.6 M, [Pd] = 4.6 × 10-4to 4.6 × 10-6M, MeNO2, rt. The tall bars correspond to “complete conversion” and the short bars are used to report maximum turnover numbers. n.d. = no detectable amount of product after 24 hr.

[0048] FIG. 11A depicts exemplary 1H NMR spectra of SI1 in CDCl3.Attorney Docket No. 0073605-001022

[0049] FIG. 11B depicts an exemplary13C{1H} NMR spectrum of SI1 in CDCl3.

[0050] FIG. 11C depicts exemplary 1H NMR spectra of SI2 in CDCl3.

[0051] FIG. 11D depicts an exemplary 13C{1H} NMR spectrum of SI2 in CDCl3.

[0052] FIG. 11E depicts exemplary 1H NMR spectra of L1 in CD3CN.

[0053] FIG. 11F depicts an exemplary 13C{1H} NMR spectrum of L1 in CD3CN.

[0054] FIG. 11G depicts exemplary 1H NMR spectra of L2 in CD2Cl2.

[0055] FIG. 11H depicts an exemplary 13C{1H} NMR spectrum of L2 in CD2Cl2.

[0056] FIG. 11I depicts exemplary 1H NMR spectra of L3 in CD3CN.

[0057] FIG. 11J depicts an exemplary 13C{1H} NMR spectrum of L3 in CD3CN.

[0058] FIG. 11K depicts exemplary 1H NMR spectra of [1][BF4]2 in CD3CN.

[0059] FIG. 11L depicts an exemplary 13C{1H} NMR spectrum of [1][BF4]2 in CD3CN.

[0060] FIG. 11M depicts exemplary 1H NMR spectra of [2][BF4]2 in CD3CN.

[0061] FIG. 11N depicts an exemplary 13C{1H} NMR spectrum of [2][BF4]2 in CD3CN.

[0062] FIG. 11O depicts exemplary 1H NMR spectra of 3 in CD2Cl2.

[0063] FIG. 11P depicts an exemplary 13C{1H} NMR spectrum of 3 in CD2Cl2.

[0064] FIGS. 11Q-R depict exemplary 1H NMR spectra collected immediately after generationof [4][BF4]2and after sitting at room1for 12 hours (below dotted line). An H NMRspectrum of single crystals of SI5 and an 1H NMR spectrum collected immediately after addition of3 equivalents of L3 to [Pd(MeCN)4]2+(above dotted line) are also shown. (400 MHz, CD3CN).

[0065] FIG. 11S depicts a solution-phase IR spectrum of [4]2+ in CD3CN.

[0066] FIG. 12A depicts blank-corrected absorption data for titration of 1 equivalent of L3 intoa MeCN solution of [Pd(MeCN)4]2+.

[0067] FIG. 12B depicts a plot of calculated extinction coefficients (correctedabsorbance / calculated concentration) at each wavelength, based on data presented in FIG. 12A.

[0068] FIG. 12C depicts ATR-IR spectra of free ligand L1, Pd alkyl [1][BF4]2, and protonatedligand [H–L1][BF4].

[0069] FIG. 13 depicts ATR-IR spectra of [1][BF4]2 (bottom) and the corresponding Pt alkylcomplex (top).

[0070] FIG. 14 depicts ATR-IR spectra of solid L2 and the corresponding alkyl complex[2][BF4]2.Attorney Docket No. 0073605-001022

[0071] FIG. 15 depicts exemplary 1H NMR spectra (500 MHz, CD3CN) of [1]2+ (bottom), [H-L1]1+(middle), and the mixture generated from addition of 3 eq HBF4·Et2O to [1]2+.

[0072] FIG. 16 depicts exemplary 1H NMR spectra (500 MHz, CD3CN) of [2]2+ before (bottom)and after (middle) addition of 1 eq HBF4·Et2O. A reference spectrum of [H-L2]1+, generated in situ by addition of 1 eq HBF4·Et2O to L2, is shown at the top.

[0073] FIG. 17 depicts exemplary 1H NMR time course data for L1 / [2]2+ ligand exchangeexperiment (500 MHz, CD3CN).

[0074] FIG. 18 depicts exemplary 2D-EXSY data of L1 and [1][BF4]2 (500 MHz, CD3CN, 298K), consistent with data shown in FIG. 4. Mixing time = 100ms.

[0075] FIG. 19 depicts exemplary 2D-EXSY data of L1 and [1][BF4]2 (500 MHz, CD3CN, 298K). Mixing time = 200 ms.

[0076] FIG. 20 depicts exemplary 2D-EXSY data of L1 and [1][BF4]2 (500 MHz, CD3CN, 298K). Mixing time = 10 ms.

[0077] FIG. 21A depicts a schematic showing PPh3 displacing L1 from κ1-1 to produce free L1and [Pd(PPh3)2L2][BF4]2.

[0078] FIG. 21B depicts a series of exemplary 1H (left, 400 MHz, CD3CN) and 31P{1H} (right)NMR spectra monitoring the incremental addition of PPh3to [1][BF4]2. Reference spectra for L1 and [Pd(PPh3)2(MeCN)2][BF4]2are displayed on top.

[0079] FIG. 21C depicts a series of exemplary 1H (500 MHz, CD3CN) NMR spectra monitoringthe incremental addition of PPh3to [1][BF4]2. A reference spectrum for L1 is displayed on top.

[0080] FIG. 21D depicts a series of exemplary 31P{1H} (500 MHz, CD3CN) NMR spectramonitoring the incremental addition of PPh3to [1][BF4]2. A reference spectrum for [Pd(PPh3)2L2][BF4]2is displayed on top.

[0081] FIG. 22A depicts a schematic showing preparation of κ1-2 and displacing L2 therefromto produce free L2.

[0082] FIG. 22B depicts exemplary 1H NMR spectra collected over course of portion-wiseaddition of up to 2 eq PPh3to [2][BF4]2.

[0083] FIG. 22C depicts exemplary 31P{1H} NMR spectrum collected over course of portion-wise addition of up to 2 eq PPh3to [2][BF4]2. A reference spectrum for [Pd(PPh3)2(L)2][BF4]2is displayed on top.Attorney Docket No. 0073605-001022

[0084] FIG. 22D depicts exemplary UV-Vis absorption spectra collected over course of portion-wise addition of up to 1 eq PPh3to [2][BF4]2.

[0085] FIG. 23 depicts a mechanism of manipulating the shapeshifting equilibrium, consistentwith equation 3 shown in the present disclosure.

[0086] FIG. 24A depicts exemplary 1H NMR spectra of [1][BF4]2, the mixture resulting fromaddition of [Et4N][Cl], and independently prepared 3 in CD3CN.

[0087] FIG. 24B depicts a comparison of 1H NMR spectra of [1]2+, [2]2+, and theircorresponding PPh3complexes and dichloro complex [3] (500 MHz, CD3CN). Note that when 3 is dissolved in CD3CN, three species are observed (likely arising from partial ionization).

[0088] FIG. 24C depicts a comparison between the ATR-FTIR spectra of free ligand L1 and (1κ2)-Cl2.

[0089] FIG. 25A depicts a schematic of Pd(II)-catalyzed olefin isomerization and the relativeLewis acidity / basicity of various Pd complexes.

[0090] FIG. 25B depicts a proposed reaction mechanism of a Pd(II)-catalyzed olefinisomerization.

[0091] FIG. 25C depicts representative 1H NMR time course data for positional isomerizationof 1-hexene, catalyzed by [1][BF4]2(CD3CN, 500 MHz). [Pd] = 1.1mM, [1-hexene] = 150 mM in CD3CN, rt. Starting material consumption was monitored using the set of peaks at ca. 5.1-4.9 ppm (2 dd, 2H). Product formation was monitored using the peak at ca. 5.55-5.54 ppm (m, 2H).

[0092] FIG. 26 depicts representative 1H NMR time course data for isomerization of cis-stilbeneto trans-stilbene, catalyzed by [2][BF4]2(500 MHz, CD3CN).

[0093] FIG. 27 depicts representative reaction time course data for cis-trans stilbeneisomerization using [1][BF4]2, [2][BF4]2, or [Pd(MeCN)4][BF4]2. Reaction progress was monitored using peak areas and peak intensities. [Pd catalyst] = 1.5 mM (3.7 mol%), [cis-stilbene] = 38 mM.

[0094] FIG. 28 depicts an overlay of time course data for two replicates of cis-stilbeneisomerization reactions. [Pd catalyst] = 1.5 mM (3.7 mol%), [cis-stilbene] = 38 mM. The two independent experiments were carried out using different Pd and substrate solutions; solutions of [1]2+and [2]2+were prepared using two different batches of the complexes. The dotted lines serve as visual guides.Attorney Docket No. 0073605-001022

[0095] FIG. 29 depicts representative reaction time course data for cis-trans stilbeneisomerization using [1][BF4]2or [Pd(MeCN)4][BF4]2. Reaction progress monitored using peak areas. [Pd catalyst] = 2.70 mM (3.7 mol%), [cis-stilbene] = 71 mM.

[0096] FIG. 30A depicts a comparison between the reaction half-lives of three Pd(II) catalysts,([1][BF4]2, [2][BF4]2, and [Pd(MeCN)4][BF4]2).

[0097] FIG. 30B depicts a representative plot of consumption of cis-stilbene during theisomerization of cis-stilbene, which is catalyzed by Pd catalysts κ1-1and κ1-2 ([Pd catalyst] = 9 mol%).

[0098] FIG. 30C depicts a representative plot of consumption of cis-stilbene for theisomerization of cis-stilbene with Pd catalyst ([1][BF4]2, [2][BF4]2, [Pd(MeCN)4][BF4]2, or [4][BF4]2). [Pd catalyst] = 2.7 mM (8.4 mol%), [cis-stilbene] = 29 mM.

[0099] FIG. 31 depicts representative reaction time course data for the isomerization of cis-stilbene with Pd catalyst ([2][BF4]2, [Pd(MECN)4][BF4]2, or [4][BF4]2). [Pd catalyst] = 2.7 mM (8.4 mol%), [cis-stilbene] = 29 mM.

[0100] FIG. 32 depicts representative time course data for rate comparison of cis-trans stilbeneisomerization in CD3NO2and CD3CN at room temperature. Reaction progress was monitored using product peak areas (as shown in FIGS. 22A-D). A magnified view of the CD3NO2data is shown in the inset. [Pd catalyst] = 1.5 mM (3.7 mol%), [cis-stilbene] = 38 mM.

[0101] FIG. 33 depicts representative time course data comparing 1-hexene isomerization for[1][BF4]2(left) and [2][BF4]2(right) in CD3NO2and CD3CN at room temperature. Reaction progress was monitored using starting material peak areas (as shown in FIG. 19). [Pd catalyst] = 1.1 mM (1.1 mol%), [1-hexene] = 96 mM.

[0102] FIG. 34 depicts representative 1H NMR time course data for positional isomerization ofmethyl 4-pentenoate by [1][BF4]2(CD3CN, 500 MHz).

[0103] FIG. 35 depicts representative 1H NMR time course data for positional isomerization of5-hexenenitrile by [1][BF4]2(CD3CN, 500 MHz).

[0104] FIG. 36 depicts representative 1H NMR time course data for positional isomerization ofdimethylallylmalonate by [1][BF4]2(500 MHz, CD3CN).

[0105] FIG. 37 depicts representative 1H NMR time course data for geometric isomerization ofdimethyl maleate by [1][BF4]2(CD3CN, 500 MHz).Attorney Docket No. 0073605-001022

[0106] FIG. 38 depicts representative 1H NMR time course data for positional isomerization ofpentenylphthalimide by [1][BF4]2(CD3CN, 500 MHz).

[0107] FIG. 39 depicts representative 1H NMR time course data for positional isomerization ofpentenylphthalimide by [2][BF4]2(CD3CN, 500 MHz).

[0108] FIG. 40 depicts representative reaction time course data for the positional isomerizationof pentenylphthalimide. Starting material consumption was monitored by measuring peak area of the set of signals at ca. 5.0 ppm (2 dd, 2H); product formation was monitored by measuring peak area of the signals ca. 5.5 ppm (m, 2H) as shown in FIGS. 34-35.

[0109] FIG. 41 depicts representative 1H NMR time course data for the positional isomerizationof N-(4-tert-butyl)phenyl-4-pentenamide by [1][BF4]2(CD3CN, 500 MHz).

[0110] FIG. 42 depicts representative 1H NMR time course data for the positional isomerizationof N-(4-tert-butyl)phenyl-4-pentenamide by [2][BF4]2(CD3CN, 500 MHz).

[0111] FIG. 43 depicts representative time course data for the positional isomerization of N-(4-tert-butyl)phenyl-4-pentenamide. Starting material consumption was monitored by measuring peak area of the set of signals at ca. 5.1ppm (2 dd, 2H); product formation was monitored by measuring peak area of the signals ca. 5.6 ppm (m, 2H) as shown in FIGS. 37-38.

[0112] FIG. 44 depicts representative 1H NMR (500 MHz, CD3CN) time course data forisomerization of 5-hexen-2-one using 9 mol% [1][BF4]2. [Pd] = 6.3 mM, [substrate] = 72 mM, CD3CN, rt.

[0113] FIG. 45 depicts representative 1H NMR (500 MHz, CD3CN) time course data forisomerization of 5-hexen-2-one using 9 mol% [2][BF4]2. [Pd] = 6.3 mM, [substrate] = 72 mM, CD3CN, rt.

[0114] FIG. 46 depicts representative 1H NMR (500 MHz, CD3CN) time course data forisomerization of 5-hexen-2-one using 9 mol% [Pd(MeCN)4][BF4]2. [Pd] = 6.3 mM, [substrate] = 72 mM, CD3CN, rt.

[0115] FIG. 47 depicts representative time course data for isomerization of 5-hexen-2-one (9mol% Pd catalyst). Reaction progress was monitored using relative peak area of target product 4- hexen-2-one. [Pd] = 6.3 mM, [substrate] = 72 mM, CD3CN, rt. The dotted lines serve as visual guides.

[0116] FIG. 48 depicts representative time course data for isomerization of 5-hexen-2-one (2mol% Pd catalyst).Attorney Docket No. 0073605-001022

[0117] FIG. 49 depicts representative 1H NMR time course data for positional isomerization of5-hexenone by [4][BF4]2(CD3CN, 500 MHz). Conditions: [Pd] = 1.4 mM (2 mol%), [hexenone] = 72 mM, rt.

[0118] FIG. 50 depicts representative 1H NMR time course data for isomerization of 5-hexenone by [2][BF4]2. After initial substrate was nearly fully converted (and some changes to catalyst speciation were observed), additional substrate was added at t = 267 hr.

[0119] FIG. 51 depicts representative 1H NMR time course data for positional isomerization ofeugenol by [1][BF4]2(CD3CN, 500 MHz). Conditions: [Pd] = 1.4 mM (2 mol%), [eugenol] = 72 mM, rt.

[0120] FIG. 52 depicts representative 1H NMR time course data for positional isomerization ofeugenol by [2][BF4]2(CD3CN, 500 MHz). Conditions: [Pd] = 1.4 mM (2 mol %), [eugenol] = 72 mM, rt.

[0121] FIG. 53 depicts representative time course data for the positional isomerization ofeugenol. Starting material consumption was monitored by measuring peak area of the set of signals at ca. 4.9 ppm (2 dd, 2H); product formation was monitored by measuring peak area of the signals ca. 6.1 ppm (m, 2H), as shown above in this disclosure.

[0122] FIG. 54 depicts representative 1H NMR time course data for positional isomerization ofeugenol by [Pd(MeCN)4][BF4]2(CD3CN, 500 MHz). Conditions: [Pd] = 1.4 mM (2 mol %), [eugenol] = 72 mM, rt. A Pd(0) mirror is observed within the first ca. 1 hr of the reaction.

[0123] FIG. 55 depicts representative 1H NMR time course data for positional isomerization ofeugenol by [4][BF4]2(CD3CN, 500 MHz). Conditions: [Pd] = 1.4 mM (2 mol %), [eugenol] = 72 mM, rt.

[0124] FIG. 56 depicts representative results for isomerization of varying equivalents of polarsubstrates by Pd complexes. Conditions: [substrate] = 4.6 M, [Pd] = 0.0046 mM – 0.46 mM, MeNO2, rt. Turnover numbers observed for 1 × 106equivalents of substrate are displayed in the inset; n.d. = no detectable amount of product after 24 hr.

[0125] FIGS. 57A-B depict two kinetic models describing a multi-step catalytic processpertaining to the present disclosure.

[0126] FIG. 57C depicts results of kinetic simulations for a catalytic reaction, with r.d.s. thatbecomes competitive with other steps; (a) structurally static case; (b) concentration suppression (kBC1= 0); (c) rate accelerations (kBC1 = kBC2, 5 × kBC2, 10 × kBC2, respectively).Attorney Docket No. 0073605-001022

[0127] FIG. 58 depicts results of kinetic simulations for a catalytic reaction with slow r.d.s.; (a)structurally static case; (b) dynamic case with concentration suppression of one state (kBC1= 0); (c) dynamic case where rate of slow step is same for each state (kBC1= kBC2) or accelerated for one state (2 × kBC2, 5 × kBC2, respectively), manifesting in overall rate acceleration.

[0128] FIG. 59 depicts results of kinetic simulations for a catalytic reaction with varying rate ofB2 / B1 interconversion; (a) rate of r.d.s. is much faster from B1 than B2; (b) rate of r.d.s. is comparable between states B1 and B2.

[0129] FIG. 60 depicts computed free energies for ligand exchange from Scheme 2.

[0130] FIG. 61A depicts a reaction coordinate diagram for cis-stilbene isomerization catalyzedby [1][BF4]2.

[0131] FIG. 61B depicts a reaction coordinate diagram for cis-stilbene isomerization catalyzedby [2][BF4]2.

[0132] FIGS. 62A-V depict optimized geometries of various chemical species discussed in thepresent disclosure.

[0133] FIGS. 63A-E depict crystal structures of various chemical species discussed in thepresent disclosure.

[0134] FIG. 64 depicts a schematic illustrating a continuum of ligand binding affinities ofvarious dicationic Pd compounds and a comparison between a traditional approach of ligand binding and the approach adopted by the present disclosure. The binding affinity of weak-field ligands can be enhanced by coupling ligation with an additional downhill reaction. Tuning the magnitude of this step provides an opportunity to manipulate ligand binding affinity without meaningfully perturbing the metal electronics.

[0135] FIG. 65 depicts an exemplary plot showing a correlation between the wavenumber ofC≡N bond and the difference in chemical shift between observed31P peaks and the reference31P peak of PPh3O. The structure of a model compound for κ2–[1]2+(see FIG. 64) is illustrated. Estimates of Lewis acidity (based on FTIR & Gutmann-Beckett) suggest that this compound is weakly ligated.

[0136] FIG. 66 depicts variable-temperature UV / Vis spectra of [1]2+. These data indicate that atemperature-dependent equilibrium is operable. Comparison with the steady-state absorption spectraof [2]2+suggests that the ligand cyclization equilibrium shifts toward κ2–[1]2+at low temperature.Attorney Docket No. 0073605-001022

[0137] FIG. 67A depicts a schematic illustrating the preparation of a Pd complex from L1. L1can be further modified with the intent of perturbing the cyclization equilibrium. The derivative ligands can be compared based on the observed binding mode when ligated to neutralize a PdII, which should decrease the propensity for ligand cyclization.

[0138] FIG. 67B depicts a schematic illustrating the preparation of a Pd complex from L3. Twohydrogen atoms in L1 are replaced by two methyl groups, as seen in L3, and the resulting L3 enhances the stability of the cyclized ligand. Metalation with neutral precursor Pd(MeCN)2Cl2generates a κ1-bound zwitterionic complex.

[0139] FIG. 68 depicts exemplary 1H NMR spectra (400 MHz, CD3CN) describing an exchangereaction between [1]2+and L3. [1]2+and L3 undergo ligand exchange to cleanly generate [3]2+and L1 – further suggesting that the binding affinity of L3 is greater than that of L1.

[0140] FIG. 69 depicts an exemplary schematic showing the binding affinity and thermalstability of various Pd complexes described in this disclosure. Keqfor ligand cross exchange experiments were determined via1H NMR and used to order the relative binding affinities of derivative ligands. Increasing binding affinity and thermal stability were observed for several modified Pd complexes (e.g., the L3-based compound and the compound containing a 6-membered ring instead of a 5-membered ring under κ1mode) with respect to reference Pd complexes based on L1 and L2; the most stable derivatives can be refluxed in MeCN for over one week without decomposing.

[0141] FIG. 70 depicts an exemplary schematic pertaining to the protonolysis of Pd complexes,showing a correlation between cyclization driving force and protic stability. Attempted protonolysis of κ1–complex yields a N-protonated free ligand. Ligand protonation likely occurs from the κ2– complex and the overall Keqfor this reaction is therefore reflective of the magnitude of ligand cyclization equilibrium.

[0142] FIG. 71 depicts the change in Gibbs free energy for cyclization processes, ΔGcyclization,and pKas of various Pd complexes. Pd alkyl derivatives exhibit varying levels of resistance toprotonolysis. The most stable derivatives do not react with excess HBF4 or TfOH. Ligand cyclizationtherefore significantly increases protection from protonation.

[0143] FIG. 72 depicts exemplary data showing catalytic performance of the Pd complexesdescribed herein. Enhancing ligand binding affinity may increase catalyst lifetime for olefinisomerization of protic substrates. Maximum turnover number was determined for each catalyst byAttorney Docket No. 0073605-001022 increasing substrate concentration until < 95% conversion was obtained. Observed maximum turnover numbers (TONs) are higher for ligands with higher binding affinities.

[0144] FIG. 73 depicts simplified mechanistic considerations for a copolymerization reaction.Methyl acrylate is used as an exemplary polar monomer. The clover sign represents a ligand.

[0145] FIG. 74 depicts a comparison between existing strategies and the present work.

[0146] FIG. 75 depicts an exemplary schematic of polymerization or copolymerization reactionsusing polar monomers (e.g., a eugenol-like styrene derivative).

[0147] FIG. 76 depicts an exemplary synthetic strategy for generating glycidyl azide polymer(GAP).

[0148] FIG. 77 depicts an exemplary synthetic strategy for increasing energetic content andderivatization to triazole.

[0149] FIG. 78 depicts an exemplary schematic showing the degradation mechanism of[(L1)Pd(Me(CN)3]2+.

[0150] FIG. 79 depicts an exemplary schematic showing thermodynamic cycles for ligandbinding affinity.

[0151] FIG. 80 depicts an exemplary schematic showing four exemplary shapeshifting ligands.

[0152] FIG. 81 depicts an exemplary schematic describing the preparation of[(L4)(MeCN)PdCl2] according to FIG. 80.

[0153] FIG. 82 depicts a conceptual evolution of catalysts for olefins described in the presentdisclosure.

[0154] FIG. 83 depicts various ligation strategies based on reactions between protonatedligands, polar substrates, and Pd-containing precursors.

[0155] FIG. 84 depicts reaction mechanisms of α- and β-insertions in polymerization.

[0156] FIG. 85 depicts stereoisomerism as a key feature for displacing polar monomer.

[0157] FIG. 86 depicts accelerating stereoisomerism as a key feature for displacing polarmonomer.

[0158] FIG. 87 depicts exemplary data including wavenumbers of C≡N bonds in various Pdcomplexes and the shift in wavenumber with respect to a reference [PdL4]2+complex. Catalytic activity of these Pd complexes is consistent with the two-state catalytic mechanism described herein.

[0159] FIG. 88 depicts various isomerization and polymerizations that can be catalyzed by theshapeshifting catalysts described in the present disclosure.Attorney Docket No. 0073605-001022

[0160] FIG. 89 depicts exemplary time course data of the isomerization reaction from cis-stilbene to trans-stilbene catalyzed by various Pd-containing complexes described herein.

[0161] FIG. 90 depicts a catalytic cycle of isomerization of 5-hexen-2-one, a polar substrate.

[0162] FIG. 91 depicts exemplary time course data of the conversion from 5-hexen-2-one to 4-hexen-2-one, using [Pd(MeCN)4]2+as a catalyst. S = MeCN.

[0163] FIG. 92 depicts exemplary data of catalytic conversion from 5-hexen-2-one to 4-hexen-2-one, using [(L1)Pd(MeCN)3]2+as a catalyst. S = MeCN.

[0164] FIG. 93 depicts exemplary data of catalytic conversion from 5-hexen-2-one to 4-hexen-2-one, using [(L2)Pd(MeCN)3]2+as a catalyst. R = C6H4-t-butyl. S = MeCN.

[0165] FIG. 94 depicts various exemplary polar substrates compatible with the shapeshiftingcatalysts described herein.

[0166] FIGS. 95-102 depict various reaction mechanisms (e.g., protonolysis) pertaining to thePd complexes described herein and associated thermodynamic data.

[0167] FIGS. 103-104 depict schematics describing preparations of various Pd complexesdescribed herein.

[0168] FIG. 105 depicts the preparation of a polystyrene homopolymer and a hydroxylatedstyrene / styrene copolymer (e.g., a copolymer of 4-vinylphenol and styrene) using the shapeshifting catalysts described in the present disclosure.

[0169] FIG. 106 depicts an exemplary styrene / styrene copolymer film and its degradation in air.

[0170] FIG. 107 depicts the evolution of IR spectra for a hydroxylated styrene / styrenecopolymer produced using the shapeshifting catalysts described herein.

[0171] FIG. 108 depicts thermogravimetric analysis (TGA) and differential scanningcalorimetry (DSC) data of a polystyrene homopolymer prepared using the shapeshifting catalysts described herein.

[0172] FIG. 109 depicts 1H diffusion-ordered spectroscopy (1H DOSY) data of the polystyrenehomopolymer in FIG. 108.weight average molecular weight (Mw) determined by1H DOSY is ca. 3200 Da, in line with the Mwdetermined by gel permeation chromatography (GPC), which is ca. 3400 Da.

[0173] FIG. 110 depicts thermogravimetric analysis (TGA) and differential scanningcalorimetry (DSC) data of a hydroxylated styrene / styrene copolymer prepared using the shapeshifting catalysts described herein.Attorney Docket No. 0073605-001022

[0174] FIG. 111 depicts a comparison between IR spectra of hydroxylated styrene / styrenecopolymer films freshly cast from acetone and aged for ca. one month, respectively. The hydroxylated styrene / styrene copolymer film was prepared using the shapeshifting catalysts described herein.

[0175] FIG. 112 depicts exemplary 1H NMR spectra (400 MHz, CDCl3) of a dimerized productof 4-styrenesulfonate. The dimerized product is synthesized using a shape-shifting catalyst described herein, specifically 0.5 mol% of [1][BF4], in nitromethane (MeNO2) at room temperature.

[0176] FIG. 113 depicts an exemplary thermal ellipsoid of a shape-shifting catalyst describedherein, specifically [1], prepared as a triflate salt. The thermal ellipsoid plot is presented at 50% probability level. H atoms are omitted for clarity.

[0177] FIG. 114 depicts exemplary 1H NMR spectra (500 MHz, CD3CN) of the shape-shiftingcatalyst shown in FIG. 113.

[0178] FIG. 115 depicts exemplary 1H NMR spectra (500 MHz, CD3CN) of a shape-shiftingcatalyst described herein, specifically [1], prepared as a hexafluoroborate salt.

[0179] FIG. 116 depicts an exemplary solid-phase ATR-IR spectrum of the shape-shiftingcatalyst shown in FIG. 115.

[0180] FIG. 117 depicts exemplary 1H NMR spectra (500 MHz, CD3CN) of a shape-shiftingcatalyst described herein, specifically [1], prepared as a tetrakis(3,5- bis(trifluoromethyl)phenyl)borate salt.

[0181] The drawings are not necessarily to scale and may be illustrated by phantom lines,diagrammatic representations, and fragmentary views. In certain instances, details that are not necessary for an understanding of the embodiments or that render other details difficult to perceive may have been omitted. DETAILED DESCRIPTION

[0182] To facilitate the understanding of this invention, a number of terms are defined belowand throughout the disclosure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. The terminology herein is used to describe specific embodiments of the invention, but their usage does not limit the invention, except as outlined in the claims. All publications, patentAttorney Docket No. 0073605-001022 applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

[0183] It is to be understood that any aspect and / or element of any embodiment of themethod(s) described herein or otherwise may be combined in any way to form additional embodiments of the method(s), all of which are within the scope of the method(s).

[0184] Where a process is described herein, those of ordinary skill in the art will appreciatethat the process may operate without any user intervention. In another embodiment, the process includes some human intervention (e.g., a step is performed by or with the assistance of a human).

[0185] As used herein, including the claims, the phrase “at least some” means “one or more”and includes the case of only one. Thus, e.g., the phrase “at least some ABCs” means “one or more ABCs” and includes the case of only one ABC.

[0186] As used herein, including the claims, the term “at least one” should be understood asmeaning “one or more” and therefore includes both embodiments that include one or multiple components. Furthermore, dependent claims that refer to independent claims that describe features with “at least one” have the same meaning, both when the feature is referred to as “the” and “the at least one”.

[0187] As used herein, the term “portion” means some or all. Therefore, for example, “a portionof X” may include some of “X” or all of “X”. In the context of a conversation, the term “portion” means some or all of the conversation.

[0188] As used herein, including the claims, the phrase “using” means “using at least” and isnot exclusive. Thus, e.g., the phrase “using X” means “using at least X”. Unless specifically stated by use of the word “only”, the phrase “using X” does not mean “using only X”.

[0189] As used herein, including the claims, the phrase “based on” means “based in part on” or“based, at least in part, on” and is not exclusive. Thus, e.g., the phrase “based on factor X” means “based in part on factor X” or “based, at least in part, on factor X”. Unless specifically stated by use of the word “only”, the phrase “based on X” does not mean “based only on X”.

[0190] In general, as used herein, including the claims, unless the word “only” is specificallyused in a phrase, it should not be read into that phrase.

[0191] As used herein, including the claims, the phrase “distinct” means “at least partiallydistinct”. Unless specifically stated, distinct does not mean fully distinct. Thus, e.g., the phrase “X isAttorney Docket No. 0073605-001022 distinct from Y” means that “X is at least partially distinct from Y” and does not mean that “X is fully distinct from Y”. Thus, as used herein, including the claims, the phrase “X is distinct from Y” means that X differs from Y in at least some way.

[0192] It should be appreciated that the words “first”, “second”, and so on, in the descriptionand claims, are used to distinguish or identify, and not to show a serial or numerical limitation.

[0193] Similarly, letter labels (e.g., “(A)”, “(B)”, “(C)”, and so on, or “(a)”, “(b)”, and so on)and / or numbers (e.g., “(i)”, “(ii)”, and so on) are used to assist in readability and to help distinguish or identify, and are not intended to be otherwise limiting or to impose or imply any serial or numerical limitations or orderings. Similarly, words such as “particular”, “specific”, “certain”, and “given”, in the description and claims, if used, are to distinguish or identify, and are not intended to be otherwise limiting.

[0194] As used herein, including the claims, the terms “multiple” and “plurality” mean “two ormore,” and include the case of “two”. Thus, e.g., the phrase “multiple ABCs” means “two or more ABCs” and includes “two ABCs”. Similarly, e.g., the phrase “multiple PQRs” means “two or more PQRs” and includes “two PQRs”.

[0195] The present invention also covers the exact terms, features, values, and ranges, etc., incase these terms, features, values, and ranges, etc., are used in conjunction with terms such as “about”, “around”, “generally”, “substantially”, “essentially”, “at least”, etc. Thus, e.g., “about 3” or “approximately 3” shall also cover exactly 3, and “substantially constant” shall also cover exactly constant.

[0196] As used herein, unless stated otherwise, the terms “about” or “approximately” refer to avalue that is within 10% above or below the value being described.

[0197] As used herein, including the claims, singular forms of terms are to be construed as alsoincluding the plural form and vice versa, unless the context indicates otherwise. Thus, it should be noted that as used herein, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. In other words, terms such as “a”, “an”, and “the” are not intended to refer to only a singular entity but include the general class of which a specific example may be used for illustration.

[0198] Throughout the description and claims, the terms “comprise”, “including”, “having”,“contain”, and their variations should be understood as meaning “including but not limited to” and are not intended to exclude other components unless specifically so stated.Attorney Docket No. 0073605-001022

[0199] It will be appreciated that variations to the embodiments of the invention can be madewhile still falling within the scope of the invention. Alternative features serving the same, equivalent, or similar purpose can replace features disclosed in the specification, unless stated otherwise. Thus, unless stated otherwise, each feature disclosed represents one example of a generic series of equivalent or similar features.

[0200] Use of exemplary language, such as “for instance”, “such as”, “for example”(“e.g.,”), and the like, is merely intended to better illustrate the invention and does not indicate a limitation on the scope of the invention unless specifically so claimed.

[0201] While the invention has been described in connection with what is presentlyconsidered to be the most practical and embodiments thereof are further described in the examples below, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0202] The following description sets forth various examples along with specific details toprovide a thorough understanding of claimed subject matter. It will be understood by those skilled in the art, however, that claimed subject matter may be practiced without one or more of the specific details disclosed herein. Further, in some circumstances, well-known methods, procedures, systems, and / or components have not been described in detail in order to avoid unnecessarily obscuring claimed subject matter. The illustrative embodiments described in the detailed description and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

[0203] Synthetic polymers are ubiquitous in daily life. Most of these plastics are nonpolarhydrocarbons, for example polyolefins (~50%, e.g., polyethylene and polypropylene) and polystyrene. The annual polyolefin production capacity is estimated at 120 million tons and greater than 200 billion USD in market value per year. While these polymers clearly have desirable properties, they are comprised (predominantly) of strong, nonpolar C–C and C–H bonds. Certain properties are difficult to design into the resulting hydrophobic polymers – e.g., adhesion, solubility, dyability and miscibility / compatibility (for making polymer blends).Attorney Docket No. 0073605-001022

[0204] Copolymers often include (a) the parent monomer and (b) a small percentage of aderivative functionalized monomer can retain the attractive properties of the parent polymer while introducing new, desired properties. For example, copolymers of ethylene and carbon monoxide have similar melting point, crystallization point, elasticity, and tensile strength to polyethylene. The copolymer is also more photodegradable than pure polyethylene. Because these copolymers are so similar to the parent polymers, they are also strong candidates for retaining use of existing industrial infrastructure. Therefore, olefin / polar monomer copolymerization is a leading possibility for designing next-generation synthetic polymers.

[0205] Polyketones (Carilon / Poketone), first launched in 1996, can serve as a relevant casestudy. Structurally, these materials differ from standard polyolefins because they feature ketone units – from feeding CO in various percentages as a comonomer. Originally, only perfectly alternating polymers could be synthesized. However, the high CO content resulted in polymers with higher melting temperatures, reducing processability. Recent advancements in catalyst design have led to non-perfectly alternating copolymers, lowering CO content to below 10%. These new polymers have more attractive properties (i.e., retaining the chemical and mechanical properties of polyethylene, including now melting at 118 °C), which has reinvigorated interest in developing polyketones. A production line with capacity of 50 kt yr-1was built in 2015. Applications for polyketones are expanding, including into high-profit markets that have not been penetrated by traditional polyolefins (e.g., the biomedical industry). The diverse range of applications results in a diverse set of regulatory environments. For example, in some markets, polyketones are marketed as “sustainable alternatives” to polyethylene.

[0206] Based on the success for the polyketones, the community generally believes thatderivative polymers incorporating polar groups in small percentages can retain the attractive properties of polyolefins and allow for the design of new properties. This strategy for obtaining new polymer properties is appealing because: (1) the raw material costs are minimally changed from those of polyolefins (adding only a small percentage of an additional comonomer) and (2) these copolymers are more likely to be able to use existing infrastructure for processing polyolefins.

[0207] The industrial community – especially Dow Chemical Company – has repeatedlyexpressed a need for controlled copolymerization of nonpolar and polar monomers. The resulting copolymers retain the processability of the parent polymer while introducing new, desirable properties (like photodegradability or deformability). These derivative copolymers are more likely toAttorney Docket No. 0073605-001022 continue using existing industrial infrastructure than polymers comprised of only a new monomer. Furthermore, the small quantity of the polar monomer only marginally changes the cost of materials.

[0208] For designing polymers, catalysts that can control the polymer microstructure(distribution of monomers, chain branching, tacticity) are needed. Large plastic manufacturers appear to maintain a portfolio of polymerization catalysts, often based on a common set of metal / ligand complexes, which are tuned from a parent catalyst to obtain desired polymer designs. The process itself also alters the composition of the polymer.

[0209] Right now, these copolymers are predominantly accessed through free radical reactionsat high temperatures and pressures. These conditions make it difficult to control the polymer microstructure and dispersity – preventing access to desired physical and mechanical properties. Therefore, these next-generation designer polymers have yet to be realized. Ethylene / carbon monoxide (CO) copolymers are an exception to this generalization, as they can be synthesized under mild conditions to yield the desired composition and distribution of molecular weights. These copolymers have even been commercialized and sold, first by Shell (as Carilon) and now by Hyosung (as POKETONE).

[0210] Specialized palladium (Pd) catalysts are the inventions that led to commercialization forethylene / CO copolymers. However, the design strategies that were used for these catalysts result only in tolerance for a single polar monomer: CO. To crudely explain the problem, for metal- catalyzed polymerization reactions, monomers first associate to an electrophilic Pd complex; they subsequently insert into the growing polymer (coordination-insertion polymerization). However, nonpolar ethylene is a weak nucleophile; polar CO is more nucleophilic. So, to obtain a copolymer that is predominantly ethylene, the less reactive monomer should somehow be incorporated more than the more reactive polar monomer. In addition, when CO (the polar monomer) binds to the catalyst, the association can be so strong that the binding event permanently deactivates the catalyst (this statement is helpful but also an oversimplification). The commercialized Pd catalysts were invented in a thirty-year campaign that tuned catalyst electrophilicity – striking a delicate balance of being electrophilic enough to activate nonpolar olefins, but not so electrophilic that CO binds irreversibly. Catalysts for other nonpolar / polar copolymers are thought to require similar campaigns tuning electrophilicity, a challenge now termed “the polar monomer problem.”

[0211] Historically, transition metal catalysts – often the best at controlling polymer structure –are incompatible with polar monomers. Simply put, a metal catalyst must be electrophilic (LewisAttorney Docket No. 0073605-001022 acidic) to activate any olefinic monomer. This electrophilicity results in unwanted interactions with polar monomers e.g., leading to catalyst inhibition / deactivation.

[0212] There are no known catalysts that are generally tolerant of polar functional groups;commercialized catalysts to date optimize around a single polar monomer. However, studying these pre-existing processes makes it possible to infer valued performance criteria. For example, high thermal stability is needed because polymerization reactions are run at 120 °C (to prevent polymer precipitation). The present work focuses on obtaining the needed thermal stability.

[0213] The present disclosure provides an alternative strategy for imbuing Pd catalysts withtolerance for polar functional groups. As a nonlimiting example, it has been demonstrated herein that these catalysts can copolymerize nonpolar / polar monomers (generating specialty polystyrenes). These Pd catalysts equilibrate between two electronic states, rapidly alternating between the two through a reversible chemical reaction. One state is more electrophilic, for activating the olefinic monomers; the other state is more nucleophilic, to reverse unwanted associations of any polar functional group. This mechanism of polar group tolerance has proven generalizable to many polar functional groups. Therefore, the catalysts described herein, and design concepts associated thereto, can be used for generating derivative polyolefins and / or expanding the use-cases of existing polyolefins. The present disclosure provides a solution to the polar monomer problem and further expands the scope of attainable properties for the world’s most successful commercial plastics. Shapeshifting Catalyst

[0214] As used herein, a “shapeshifting catalyst” is a catalyst capable of interconvertingbetween a first configuration or state and a second configuration or state in order to perform a certain aspect of its catalytic function.

[0215] As used herein, a “catalytic function” or “catalytic activity” is a capability of a chemicalspecies to perform catalysis and function as a catalyst. As used herein, “catalysis” is a process wherein a chemical species accelerates a chemical reaction by lowering at least one activation barrier along a reaction coordinate and increases at least one rate constant associated with the at least one activation barrier. The chemical species capable of performing catalysis is accordingly classified as a catalyst. In some embodiments, to perform a catalytic function, a catalyst can first be consumed by one or more reactants to form one or more intermediates, then be regenerated as the one or more intermediates are converted to one or more products. In other words, a catalyst should not get consumed as a net result and accordingly should not be included as a reactant in a net chemicalAttorney Docket No. 0073605-001022 reaction. The catalytic function or activity of a catalyst can be described using mathematical tools or kinetic models such as Arrhenius equation, Eyring equation. Michaelis-Menten equation, Lineweaver-Burk equation, among others, as deemed suitable by a person of ordinary skill in the art upon reviewing the entirety of this disclosure.

[0216] In some embodiments, one or more reactants can bind / adsorb to a catalyst, participate ina chemical reaction, then dissociate / desorb from the catalyst as one or more products. In some embodiments, a catalyst can include a homogeneous catalyst, wherein the catalyst and reactant(s) are dispersed in the same phase (often a solution). In some embodiments, a catalyst can include a heterogeneous catalyst, wherein the catalyst and reactant(s) are dispersed in two or more distinct phases, with at least one interface in between. As a nonlimiting example, a heterogeneous catalyst can be included in a solid phase, and one or more reactants can be dispersed in a gas phase; a chemical reaction catalyzed by the heterogeneous catalyst can accordingly occur at an interface between the solid phase and the gas phase. In some embodiments, a catalyst, such as a heterogeneous catalyst, can have a large specific surface area for one or more reactants to bind / adsorb to and react. In some embodiments, a heterogeneous catalyst can be implemented as a supported catalyst. As used herein, a “supported catalyst” is a type of catalyst wherein one or more materials with catalytic activity are supported by a porous, catalytically inactive matrix to increase the specific surface area thereof.

[0217] Specifically, through ligand design, the present disclosure provides a shapeshiftingcatalyst that has access to two states. These two states are electronic dissimilar to one another – one state being highly Lewis acidic and the other being more Lewis basic. These two-state catalysts have proven generally tolerant of Lewis basic functionality but retain activity that is intrinsic to Lewis acidic catalysts.

[0218] In some embodiments, the shapeshifting catalyst has a charge-localized state in chemicalequilibrium with a charge-separated state. As used herein, a “charge-localized state” is a state in which one or more charges is located on a single atom or a single cluster of atoms. As used herein, a “charge-separated state” is a state in which one or more charges are delocalized or distributed across multiple atoms within a single chemical species.

[0219] In some embodiments, the shapeshifting catalyst has an electrophilic state in chemicalequilibrium with a nucleophilic state. As used herein, an “electrophilic” state is a state in which at least a portion of a chemical species has a relatively lower electron density and, accordingly, anAttorney Docket No. 0073605-001022 affinity for another electron-rich chemical species. As used herein, a “nucleophilic” state is a state in which at least a portion of a chemical species has a relatively higher electron density and, accordingly, an affinity for another electron-deficient chemical species.

[0220] In some embodiments, shapeshifting catalyst can have an unmasked Lewis acidic state inchemical equilibrium with a masked Lewis acidic state. As used herein, an “unmasked” Lewis acidic state is a state in which the Lewis acidity or electron deficiency of a chemical species has not been effectively suppressed, such that the chemical species is more likely to undergo a Lewis acid-Lewis base reaction with another electron-rich chemical species. As used herein, a “masked” Lewis acidic state is a state in which the Lewis acidity or electron deficiency of a chemical species is at least partially suppressed such that the chemical species is less likely to undergo a Lewis acid-Lewis base reaction with another electron-rich chemical species.

[0221] As used herein, a “chemical equilibrium” is a dynamic steady state in which a chemicalreaction proceeds in both a forward and a reverse direction, at the same reaction rate, resulting in no observable net change in the concentration or amount of either reactant(s) or product(s).

[0222] In some embodiments, the shapeshifting compound can include a coordination complex.As used herein, a “coordination complex” is a chemical species that includes a central metal atom / cation and one or more surrounding chemical species coordinating thereto by donating their electron density.

[0223] In some embodiments, the shapeshifting catalyst can include an organometalliccompound. As used herein, an “organometallic compound” is a metal-containing chemical species that contains at least one metal–carbon bond. Ligand

[0224] The shapeshifting catalyst can include a ligand. As used herein, a “ligand” is a chemicalspecies capable of binding with and / or stabilizing another chemical species, typically through coordinate covalent bond. A ligand can include a neutral molecule or an ion, and usually contains relatively polarizable elements such as C, O, N, P, S, or the like that can function as a Lewis base by donating its lone-pair electron(s) or π electrons to an electron-deficient Lewis acid species.

[0225] The ligand can undergo various types of reversible changes, including without limitationdenticity, hapticity protic state, structural rearrangements, and / or the like. Similar examples can be found in a reversible aromatization-dearomatization process that can facilitate H2activation (see e.g.,Attorney Docket No. 0073605-001022 J. Am. Chem. Soc. 2006, 128, 15390), and in a use of hemilability to achieve a 113-fold increase in oxidation addition of methyl iodide (MeI) (see e.g., J. Chem. Soc., Dalton Trans. 1974, 480).

[0226] The ligand, when under its free state (i.e., not coordinated to a metal or metal cation),can include i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker, such as without limitation an alkylene linker having a length of two to five C atoms. Aromatic N-heterocycle

[0227] As used herein, an “aromatic N-heterocycle” is a planar, conjugated chemical structurethat not only satisfies the Hückel’s rule by having (4n + 2) π electrons but also contains at least one N atom in its ring(s).

[0228] In some embodiments. the aromatic N-heterocycle can include one or more N-heterocycles selected from a group consisting of a substituted or unsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstituted oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substituted or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted or unsubstituted tetrazine, a substituted or unsubstituted purine, and a substituted or unsubstituted pteridine, wherein the one or more N-heterocycles can beAttorney Docket No. 0073605-001022 optionally fused with a substituted or unsubstituted benzene, furan, pyrrole, thiophene, indole, naphthalene, anthracene, phenathrene, chryscene, or pyrene.

[0229] In some embodiments. the aromatic N-heterocycle can include a substituted orunsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstituted oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substituted or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted or unsubstituted tetrazine, a substituted or unsubstituted purine, and / or a substituted or unsubstituted pteridine, wherein the one or more N-heterocycles can be optionally fused with a substituted or unsubstituted benzene, furan, pyrrole, thiophene, indole, naphthalene, anthracene, phenathrene, chryscene, or pyrene.

[0230] In some embodiments, the aromatic N-heterocycle can include a condensed N-heterocycle of two or more members selected from a group consisting of a substituted or unsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstitutedAttorney Docket No. 0073605-001022 oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substituted or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted or unsubstituted tetrazine, a substituted or unsubstituted purine, and a substituted or unsubstituted pteridine.

[0231] In some embodiments, the aromatic N-heterocycle can include a condensed N-heterocycle of a substituted or unsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstituted oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substituted or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted orAttorney Docket No. 0073605-001022 unsubstituted tetrazine, a substituted or unsubstituted purine, and / or a substituted or unsubstituted pteridine.

[0232] In some embodiments, the aromatic N-heterocycle can include a 14- or 18-electron πsystem. Alkenyl Group

[0233] As used herein, an “alkenyl group” is a chemical structure derived from an alkenemolecule and represented by a general formula –CnH2n-1. As a nonlimiting example, an alkenyl group can include a vinyl group, –CH=CH2, which is derived from ethylene (CH2=CH2). As a nonlimiting example, an alkenyl group can include an allyl group, –CH2–CH=CH2, which is derived from propene (CH3–CH=CH2).

[0234] In some embodiments, one or more H atoms of the alkenyl group can be substituted by ahalogen atom, a straight-chain alkyl group having 1-12 C atoms, a branched or cyclic alkyl group having 3-12 C atoms, an alkenyl or alkynyl group having 2-12 C atoms, or an aryl group having 6-12 C atoms. In some embodiments, one or more H atoms of the alkenyl group can be substituted by a - C6H4-C(CH3)3group, wherein the t-butyl (-C(CH3)3) group can be positioned at the ortho, meta, or para position with respect to the alkenyl group. Transition Metal Cation

[0235] In some embodiments, the transition metal cation can be a cation of a metal elementfrom Group 4 (Ti, Zr, Hf), 6 (Cr, Mo, W), 9 (Co, Rh, Ir), 10 (Ni, Pd, Pt), or 11 (Cu, Ag, Au) of the periodic table. In some embodiments, the transition metal cation can be a cation of Pd or Pt. In some embodiments, the transition metal cation can be a divalent or multivalent cation. In some embodiments, the transition metal cation can be Pd(II). Denticity

[0236] As used herein, “denticity” or “κ” is the number of atoms or groups of atoms with whicha ligand binds to a metal center in a coordination complex. Denticity should be differentiated from hapticity (η), which is the number of contiguous atoms in a ligand that are bonded to a metal center. As a nonlimiting example, when an alkene functions as a ligand, its denticity is κ = 1, whereas its hapticity is η = 2.

[0237] The shapeshifting catalyst changes its structure and reactivity as the ligand undergoesrearrangement and changes its binding mode. When under the charge-localized, electrophilic, and / or unmasked Lewis acidic state, the ligand coordinates to the transition metal cation in a bidentateAttorney Docket No. 0073605-001022 mode (κ = 2) through an N atom of the aromatic N-heterocycle and the alkenyl (i.e., olefin) group, e.g., in a κ2-pyrimidine / olefin mode. When under the charge-separated, nucleophilic, and / or masked Lewis acidic state, the ligand coordinates to the transition metal cation in a monodentate mode (κ = 1), e.g., in a monoanionic κ1-alkyl mode. The unmasked Lewis acidic state and the masked Lewis acidic state can interconvert to each other through formation or dissociation of a C–N bond.

[0238] In some embodiments, the formation or dissociation of the C–N bond is accompanied bya cyclization or retrocyclization of a five- six, seven-, or eight-membered ring, depending on the length of the alkylene linker. Additional details will be provided below in this disclosure. Alkylene Linker

[0239] As used herein, an “alkylene linker” is a chemical structure derived from an alkane andrepresented by a general formula –CnH2n–.

[0240] In some embodiments, one or more H atoms of the alkylene linker can each besubstituted by a halogen atom, a straight-chain alkyl group having 1-12 C atoms, a branched or cyclic alkyl group having 3-12 C atoms, an alkenyl or alkynyl group having 2-12 C atoms, or an aryl group having 6-12 C atoms. In some embodiments, one or more H atoms of the alkylene linker can each be substituted by a methyl group. Thermodynamic Stability

[0241] In some embodiments, the charge-separated, nucleophilic, or masked Lewis acidic statecan have a comparable stability to that of the respective charge-localized, electrophilic, or unmasked Lewis acidic state. In some embodiments, the charge-separated, nucleophilic, or masked Lewis acidic state can be thermodynamically more stable (i.e., associated with a lower Gibbs free energy) than the respective charge-localized, electrophilic, or unmasked Lewis acidic state. In some embodiments, the charge-separated, nucleophilic, or masked Lewis acidic state can have a Gibbs free energy that is lower than that of the respective charge-localized, electrophilic, or unmasked Lewis acidic state by no more than 30 kcal mol-1. As nonlimiting examples, the charge-separated, nucleophilic, or masked Lewis acidic state can have a Gibbs free energy that is lower than that of the respective charge-localized, electrophilic, or unmasked Lewis acidic state by no more than 2 kcal mol-1, no more than 3 kcal mol-1, no more than 4 kcal mol-1, no more than 5 kcal mol-1, no more than 10 kcal mol-1, no more than 15 kcal mol-1, no more than 20 kcal mol-1, no more than 25 kcal mol-1, no more than 30 kcal mol-1, and / or the like. As another nonlimiting example, the charge-separated, nucleophilic, or masked Lewis acidic state can have a Gibbs free energy that is lower than that of theAttorney Docket No. 0073605-001022 respective charge-localized, electrophilic, or unmasked Lewis acidic state by at least 0.1 kcal mol-1, at least 0.2 kcal mol-1, at least 0.5 kcal mol-1, at least 1 kcal mol-1, at least 5 kcal mol-1, at least 10 kcal mol-1, at least 15 kcal mol-1, and / or the like. Additional Features

[0242] In some embodiments, the shapeshifting catalyst can further include one or more labileligands coordinated to the transition metal cation. As used herein, a “labile” ligand is a ligand with a relatively lower binding affinity to the transition metal cation that can be displaced by a ligand with a stronger binding affinity. In some embodiments, at least one labile ligand of the one or more labile ligands can be an acetonitrile molecule.

[0243] In some embodiments, the shapeshifting catalyst can be a tetrafluoroborate (BF4-) salt, ahexafluoroborate (PF6-) salt, a trifluoromethanesulfonate or triflate (CF3SO3-) salt, or a tetrakis(3,5- bis(trifluoromethyl)phenyl)borate ([{3,5-(CF3)2C6H3}4B]-) salt of a cationic (i.e., positively charged) coordination complex. The cationic coordination complex can be produced by a chemical reaction between the ligand, the transition metal cation, and optionally one or more labile ligands.

[0244] In some embodiments, the transition metal cation can have a coordination number offour or six. Accordingly, in some embodiments, the transition metal cation can have a square planar or octahedral coordination geometry.

[0245] In some embodiments, both the charge-localized state and the charge-separated state canbe catalytically active and capable of simultaneously driving one or more chemical transformations. In some embodiments, only the charge-localized state can be catalytically active. Method of Preparation

[0246] Another aspect of the present disclosure is a method of preparing the shapeshiftingcatalyst. The method includes metalating the ligand using a salt or coordination complex of the transition metal cation. In some embodiments, a coordination complex with one or more labile ligands, such as without limitation [Pd(MeCN)4][BF4]2, can be used for preparing the shapeshifting catalyst. Use / Method of Use

[0247] The method of using the shapeshifting catalyst includes providing a catalytically activeamount of the shapeshifting catalyst to one or more organic substrates and transforming the one or more organic substrates into one or more products. As used herein, a “catalytically active” amount is a quantity of the shapeshifting catalyst that is sufficient for completing a chemical reaction in aAttorney Docket No. 0073605-001022 reasonable time frame. The catalytically active amount can include any amount or concentration deemed suitable or relevant by a person of ordinary skill in the art, upon reviewing the entirety of this disclosure. As a nonlimiting example, the shapeshifting catalyst can be provided at an amount of at least 0.0001 mol% and no greater than 5 mol% of the reaction mixture, including any subrange therein.

[0248] In some embodiments, the one or more organic substrates can be unsaturated and / orcontain one or more C=C bonds. In some embodiments, at least one organic substrate of the one or more organic substrates can be an unsubstituted or substituted olefin or styrene.

[0249] In some embodiments, at least one organic substrate or the one or more substrates caninclude a polar functional group. In some embodiments, the polar functional group can be selected from a list consisting of an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester, a sulfonate ester, a sulfonate ion, a halogen, and a pyridinyl group. In some embodiments, the polar functional group can be an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester, a sulfonate ester, a sulfonate ion, a halogen, and / or a pyridinyl group.

[0250] In some embodiments, the shapeshifting catalyst can be used for an isomerization,oligomerization, telomerization, and / or polymerization or copolymerization reaction.

[0251] As used herein, “isomerization” is a chemical process of converting a chemical speciesto one or more of its isomers. As nonlimiting examples, the shapeshifting catalysts described herein can be used to drive a cis-trans isomerization, an E-Z isomerization, positional isomerization, and / or the like.

[0252] As used herein, “oligomerization” is a chemical process of synthesizing an oligomer. Asused herein, an “oligomer” is a chemical species that includes a few, typically 2-40, repeating monomer units. An oligomer should be contrasted to a polymer, which is usually understood to have a large number of units, possibly thousands or millions. However, there is no sharp distinction between the two. Additional details regarding polymers are provided below in this disclosure.

[0253] As used herein, “telomerization” is a chemical process of synthesizing a telomer. Asused herein, a “telomer” is a particular kind of oligomer with two distinct end groups. As a nonlimiting example, telomerization can include a linear dimerization of 1,3-dienes with simultaneous addition of a nucleophile.Attorney Docket No. 0073605-001022

[0254] As used herein, “polymerization” is a chemical process for synthesizing a polymer. Asused herein, a “polymer” is a large molecule with repeating structural units connected to one another by covalent chemical bonds. The terms polymer and macromolecules are often used interchangeably. As nonlimiting examples, a polymer can be prepared, using the shapeshifting catalyst, from one or more monomers such as without limitation ethylene (to form polyethylene), propylene (to form polypropylene), styrene (to form polystyrene), acrylate (to form polyacrylate), acrylamide (to form polyacrylamide), methacrylate (to form polymethacrylate), methacrylamide (to form polymethacrylamide), vinyl ester (to form polyvinyl ester), vinyl amide (to form polyvinyl amide), and / or the like.

[0255] More specifically, the shapeshifting catalyst described herein can be used forhomopolymerization or copolymerization. As used herein, “homopolymerization” is a chemical process for synthesizing a homopolymer. As used herein, a “homopolymer” is a polymer derived from a single type of monomer. As used herein, “copolymerization” is a chemical process for synthesizing a copolymer. As used herein, a “copolymer” is a type of polymer derived from more than one type of monomers. Depending on the types of monomers involved, a copolymer can include a bipolymer (i.e., with two types of monomers), a terpolymer (i.e., with three types of monomers), a quaterpolymer (i.e., with four types of monomers), and / or the like. A copolymer can contain a specific ratio between different monomers, such as without limitation a 20:80 or 5:95 molar ratio for a bipolymer, a 10:80:10 molar ratio for a terpolymer, and / or the like. Additionally, depending on the type of copolymerization being used, a copolymer can accordingly be categorized as an alternating copolymer, a random copolymer, a block copolymer, a stereoblock copolymer, a periodic copolymer, a gradient copolymer, a graft copolymer, a brush copolymer, a star copolymer, and / or the like.

[0256] The shapeshifting catalysts (and catalyst design principles) described herein can beapplied to useful polymerization or copolymerization reactions. Specifically, these catalysts can be used to predictably generate organic materials with tunable properties and diffuse increasingly challenging synthetic problems. The capability of these shapeshifting catalysts in reducing or preventing Lewis base inhibition, as disclosed herein, are compatible with the design principles generated from current best-of-class catalysts. Therefore, the present disclosure provides a solution that is generalizable to many Lewis basic monomers.Attorney Docket No. 0073605-001022

[0257] As a nonlimiting example, he shapeshifting catalysts described herein have beensuccessfully applied towards the copolymerization of styrene and polar styrene-like monomers such as 4-vinylphenol; the tolerance of Lewis bases has proven transferable.

[0258] In some embodiments, the method can further include exposing the one or more organicsubstrates to the shapeshifting catalyst to facilitate a polymerization reaction, thereby producing a polymeric product. In some embodiments, the polymeric product can include polystyrene, polyethylene, or polypropylene. In some embodiments, the polymeric product can include a copolymer. In some embodiments, at least one monomer of the copolymer comprises a polar functional group. In some embodiments, the charge-separated, nucleophilic, or masked Lewis acidic state is tolerant of polar functional groups. In some embodiments, both the charge-localized, nucleophilic, or masked Lewis acidic state and the charge-separated, electrophilic, or unmasked Lewis acidic state are tolerant of polar functional groups. Article of Manufacture

[0259] In some embodiments, an article of manufacture can include the shapeshifting catalyst(s)described herein. Such article of manufacture can include catalytic systems or reactors, or polymer- based compositions containing the shapeshifting catalyst(s) or residual thereof. Nonlimiting examples of such polymer-based compositions can be found in use cases such as packaging (flexible packaging, rigid packaging, food packaging, etc.), automotives (interior components, exterior parts, overmolding and seating, etc.), consumer goods (household items, toys, electronics, etc.), construction (pipes and fittings, insulation, geotextiles, etc.), textiles (non-woven fabrics, carpet backing, apparel, etc.), medical applications (medical devices, drug delivery systems, hygienic products, etc.), agriculture (mulch films, greenhouse covers, pesticide and fertilizer containers, etc.), manufacturing (3D printing, injection molding, blown film extrusion, etc.), environmental applications (recyclable materials, biodegradable compounds, etc.), or chemicals (chemical storage, adhesives or coatings, etc.). Method of Stabilizing a Lewis-Acidic Catalyst

[0260] A method of stabilizing a Lewis-acidic catalyst is also provided based on theshapeshifting catalyst described herein. The method can include coordinating a ligand to a transition metal cation of a Lewis-acidic catalyst, the ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker having a length of two to five C atoms, wherein under the charge-localized state, the ligand coordinates toAttorney Docket No. 0073605-001022 the transition metal cation in a bidentate mode through an N atom of the aromatic N-heterocycle and the alkenyl group, under the charge-separated state, the ligand coordinates to the transition metal cation in a monodentate mode, and the charge-localized state and the charge-separated state interconvert to each other through formation or dissociation of a C–N bond. Method of Making a Polymeric Material

[0261] A method of making a polymeric material is also provided based on the shapeshiftingcatalyst described herein. The method can include providing a catalytically active amount of a shapeshifting catalyst. The shapeshifting catalyst includes a ligand having i) an aromatic N- heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker having a length of two to five C atoms and a transition metal cation, wherein, under a charge-localized state, the ligand coordinates to the transition metal cation in a bidentate mode through one or more N atoms of the aromatic N-heterocycle and the alkenyl group, under a charge- separated state, the ligand coordinates to the transition metal cation in a monodentate mode, and the charge-localized state and the charge-separated state interconvert to one another through formation or dissociation of a C–N bond. The method can further include contacting the shapeshifting catalyst with one or more organic substrates to produce a polymeric product.

[0262] In some embodiments, the polymeric product can include polystyrene, polyethylene, orpolypropylene. In some embodiments, the polymeric product can include a copolymer. In some embodiments, at least one monomer of the copolymer can include a polar functional group.

[0263] In some embodiments, the charge-separated state can be tolerant of polar functionalgroups. In some embodiments, both the charge-localized state and the charge-separated state can be tolerant of polar functional groups. In some embodiments, the polar functional group can be selected from a list consisting of an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester, a sulfonate ester, a sulfonate ion, a halogen, and a pyridinyl group. In some embodiments, the polar functional group can include an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester, a sulfonate ester, a sulfonate ion, a halogen, and / or a pyridinyl group. In some embodiments, the one or more organic substrates can be unsaturated. In some embodiments, at least one organic substrate of the one or more organic substrates can include an unsubstituted or substituted olefin or styrene.Attorney Docket No. 0073605-001022 EXAMPLES EXAMPLE 1: Shapeshifting Ligands Mask Lewis Acidity of Dicationic Palladium(II)

[0264] Supporting ligands limit the degree of electrophilic activation for any substrate becausethey also reduce the Lewis acidity of the transition metal cation. In this example, the Lewis acidity of dicationic Pd(II) is masked by using “shapeshifting” bidentate pyrimidine / olefin ligands L1 and L2. These ligands delocalize / relocalize charge via reversible C–N bond formation. So, although ligated dicationic Pd compounds [1]2+and [2]2+appear charge separated (distributed across Pd and ligand), they react comparably to a solvated Pd(II) dication. Despite reacting like strong Lewis acids, the complexes are tolerant of polar functional groups (Lewis bases that often inhibit electrophilic catalysis). This property likely originates from the installation of a more nucleophilic (charge separated) state. This case study suggests that catalysts featuring reversible dynamics can be advantaged relative to structurally static counterparts.

[0265] Upon coordination to a transition metal cation, olefins are activated by bonding andbackbonding interactions (the Dewar-Chatt-Duncanson model).1Little backbonding occurs in Lewis acidic metal / ligand complexes; the olefin will therefore lose electron density and become more electrophilic.2Eisenstein / Hoffmann1dand Sen3have both suggested that electrophilic Pd / olefin complexes can “slip” to the corresponding κ1-alkyl, generating carbonium character at the β–carbon. This mode of electrophilic activation is a key step4in catalytic reactions such as isomerization,3a, 5oligomerization,6telomerization,7and polymerization,8– some of which are run on industrial scale.

[0266] Many functional groups – not just olefins – coordinate to electrophilic metal ions. Thesecompeting Lewis acid / base interactions can inhibit olefin binding and / or temper Lewis acidity via charge stabilization.9Both effects inhibit desired reactions with olefins.10Electrophilic catalysts for olefin activation are therefore associated with poor functional group tolerance.11

[0267] One approach for mitigating these deactivation reactions is to install multidentate weakor mid-field ligands. However, because those supporting ligands are Lewis bases, they will also temper the Lewis acidity of the transition metal cation (see FIG. 1F, panel a).

[0268] The example described herein presents an alternative strategy for designing electrophilicmetal / ligand complexes: “masking” Lewis acidity via reversible mechanisms of charge stabilization (see FIG. 1F, panel b). For example, L1 and L2 are potential bidentate ligands featuring an olefin tethered to a weakly nucleophilic pyrimidine. The olefin can be activated by dicationic Pd(II) and undergo C–N bond formation. This process relocates charge from Pd to the 14 electron π-system –Attorney Docket No. 0073605-001022 reducing Lewis acidity of Pd.12However, these C–N bond forming steps are rapidly reversed,13so ligated Pd complexes might bifurcate between the more nucleophilic, charge separated state and the more electrophilic, charge localized state (a “shapeshifting”14ligand).

[0269] The syntheses of charge-separated Pd dications [1]2+ and [2]2+ (as their [BF4]– salts) aredescribed below as equations 1 and 2. As shown in equation 1, ligand cyclization relocates charge from Pd2+to L1. Delocalization over the aromatic system likely stabilizes the ligand-based charge.

[0270] Inwith chargedistribution across both Pd and the ligand. However, as catalysts, the complexes are comparable to more electrophilic species e.g., a solvated Pd dication. Additional stoichiometric experiments imply that the mechanism of charge transfer (to-and-from the Pd) is reversible. So, [1]2+and [2]2+are effectively “masked” Lewis acids. These catalysts have also proven unusually tolerant of Lewis basic functional groups. Such tolerance is likely a consequence of introducing a more Lewis basic “masking” state into the catalytic cycle. Results

[0271] Two Binding Modes for L1 / L2.

[0272] L1 and L2 can adopt either of two coordination modes: κ1-alkyl or κ2-pyrimidine / olefin.Both L1 or L2 cleanly metallate when added to a MeCN solution of [Pd(MeCN)4][BF4]2, generating [1][BF4]2or [2][BF4]2respectively (eq 1). The x-ray structures for L2 and [2][BF4]2indicate thatAttorney Docket No. 0073605-001022during metalation, an anti- addition of Pd and the pyrimidine N occurred across what was previouslythe C=C bond (see FIG. 2, panels a and b, respectively). This addition elongates the bond from 1.322(5) Å (for L2) to 1.529(6) Å. The corresponding bond in [1][BF4]2is 1.525(4) Å. These observations indicate that the ligands of [1][BF4]2and [2][BF4]2coordinate to Pd as monoanionic κ1- alkyls. The relative Pd–C bond lengths for [1][BF4]2and [2][BF4]2(2.024(3) Å vs 2.054(5) Å, respectively) suggest L1 is less sterically demanding than L2.

[0273] When L1 is metalated to Pd(MeCN)2Cl2, the ligated complex 3 (eq 2) is produced. Thex-ray structure of 3 indicates that, in this case, L1 binds as a bidentate neutral ligand (κ2- pyrimidine / olefin). The olefinic bond length (C19–C20) is 1.369(3) Å – suggesting minimal backbonding (as expected for Pd(II),1aFIG. 2, panel c). Slight asymmetry is observed in the Pd–C bond lengths (Pd–C19 is 2.187(5) Å and Pd–C20 is 2.202(5) Å).

[0274] The κ1-alkyl and κ2-pyrimidine / olefin binding modes have distinct features in infraredspectroscopy. For [1][BF4]2, strong bands are observed at 1635, 1555, and 1255 cm-1(νC=N, νC=N, νCC, and δCHrespectively). Relative to free ligand L1, these bands are 2-4 × more intense and shifted by ca. +15 cm-1(see FIG. 3).15Similar changes were observed for [2][BF4]2and free ligand L2 (FIG. 14). The IR spectrum of 3 is consistent with N-coordination to Pd.16The κ1-alkyl specific changes are consistent with C–N bond formation as a mechanism of charge transfer into the π-system of L1 / L2 (see FIG. 3). Density functional theory (DFT) calculations – performed with the PBE017functional, def2-TZVP18basis set, and conductor-like polarizable continuum model – agree with experimental observations (relative positions and intensities).19

[0275] The thermodynamically preferred coordination mode (κ1-alkyl vs κ2-pyrimidine / olefin)can be rationalized based on charge stabilization. For [1]2+and [2]2+, charge delocalization is preferred (distributed between ligand and Pd), so the ligand undergoes cyclization and is observed as a κ1-alkyl. For 3, the anionic donor ligands [Cl]–reduce the advantage for the charge separated state, so the ligand is observed as a κ2-pyrimidine / olefin.

[0276] C–N Bond Formation is Reversible

[0277] Additional experiments using [1]2+ and [2]2+ suggest that the C–N forming step can berapidly reversed (retrocyclization / C–N cleavage), as shown in Scheme 1 below. Scheme 1. Protonolysis yields N-protonation.Attorney Docket No. 0073605-001022

[0278] For example, adding greater than one equiv. of HBF4•Et2O to a solution of either κ1-alkyl regenerates [Pd(MeCN)4]2+and expels the corresponding N-protonated free ligand ([H–L1]+or [H–L2]+, Scheme 1). The N-protonolysis product implies that retrocyclization must be faster than protonation at carbon (which would yield the C-protonolysis product). Our observations are similar to previous work from Stahl, who also concluded that retrocyclization occurs rapidly.13b

[0279] Ligand self-exchange and cross-exchange experiments also imply that C–N bondformation is reversible. A mixture of L1 and [1]2+was prepared in CD3CN. In a 2D-exchange spectroscopy experiment (EXSY, 298 K, 100 ms mixing time),20exchange peaks were observed between three pairs of resonances from [1]2+and L1 (see FIG. 4). These observations indicate that ligand self-exchange is occurring, with the ligand of [1]2+equilibrating with free L1.

[0280] In a ligand cross-exchange experiment, L1 was added to a solution of [2]2+. Quantitativeconversion to [1]2+and displaced L2 was observed. No reaction was observed when L2 was added to a solution of [1]2+. These observations are consistent with a ligand exchange equilibrium, where L2 has a lower binding affinity than L1. Additional details can be found in Scheme 2 below.Attorney Docket No. 0073605-001022 Scheme 2. Ligand exchange between L1 / [2]2+and L2 / [1]2+.

[0281] When L1 / L2 are bound to Pd as monoanionic alkyl ligands, there are no obviouspathways for ligand exchange / dissociation. Again, a straightforward proposal is the microscopic reverse of C–N bond formation. This C–N cleavage can occur from either the square planar κ1-alkyl or after association of an exogenous ligand. After C–N cleavage, typical ligand exchange / dissociation pathways can be invoked. The κ2-pyrimidine / olefin is depicted in Scheme 2 because it is speculated to be the second most stable form of [1]2+and [2]2+(considering the chelate effect and the isolated complex 3).21

[0282] We probed the proposed potential energy surface depicted in Scheme 2 using DFTcalculations. Those calculations predict that the net reaction ([κ1-2]2++ [L1] → [κ1-1]2++ [L2]) is indeed downhill, by 9.6 kcal mol-1. For 1, the κ2-pyrimidine / olefin was computed as 7.2 kcal mol-1less stable than the corresponding κ1-alkyl; for 2 the two isomers are near thermoneutrality.22These values indicate that both states would have meaningful concentrations at equilibrium.Attorney Docket No. 0073605-001022

[0283] If the ligands easily interconvert between the two binding modes, then they will respondto modifications to the remaining coordination sites on Pd. It is worth noting that addition of donor ligands such as PPh3or Cl- can stabilize the metal-based charge and shift the equilibrium to favor κ2mode, as charge is more stable on metal than on the supporting ligand. For example, when two equivalents of [Et4N][Cl] are added to a CD2Cl2solution of [1]2+, generate neutral dichloride 3 is generated. The chloride ligands of 3 can also be abstracted using 2 equiv. AgBF4to generate [1]2+(eq 3, observed by1).

[0284] case. Bothcleanly generate the corresponding monophosphine complexes [1–PPh3]2+ and [2–PPh3]2+ (eq 4 andeq 5, respectively).Attorney Docket No. 0073605-001022

[0285] However, the 1H NMR spectrum for [1–PPh3]2+ resembles that of [1]2+ and [2]2+, whilethe 1H NMR of [2–PPh3]2+ does not (see FIG. 24B, measured in CD3CN). For example, the mostdownfield doublet for [1]2+, [2]2+, and [1–PPh3]2+appear at 8.37, 8.15, and 8.33 ppm, respectively (see FIG. 24B). The corresponding doublet for [2–PPh3]2+appears at 9.26 ppm and better resembles the spectroscopic features of 3 (which has a corresponding doublet at 9.09 ppm). Similarly, the IR spectrum of [1–PPh3]2+retains the strong bands at 1635, 1555, and 1255 cm-1(resembling the spectra of [1]2+and [2]2+). The corresponding bands of [2–PPh3]2+are comparatively weak, closelyresembling the spectra of 3 (see FIG. 5).

[0286] The spectroscopic data suggest that the ligand of [1–PPh3]2+ remains bound in the κ1-alkyl form and that the ligand of [2–PPh3]2+is now bound as a κ2-pyrimidine / olefin. Presumably the strong donor ligand (PPh3) stabilizes charge on the metal center – reducing the advantage for the charge separated κ1-alkyl state (bringing the two states closer to thermoneutrality). Because L2 is bulkier than L1, the ligand is more prone to retrocyclization (perturbing equilibrium for [2–PPh3]2+towards the κ2-pyrimidine / olefin). The corresponding equilibrium for [1–PPh3]2+favors the κ1-alkyl.

[0287] To summarize, these observations strongly suggest the C–N bond formation can berapidly reversed. Thus, especially in the presence of exogenous ligands, the charge separated κ1– alkyls [1]2+and [2]2+can transfer charge back-and-forth via C–N cleavage and reformation.

[0288] [1]2+ and [2]2+ as Catalytic Lewis Acids

[0289] It is anticipated that the κ1-alkyl states of [1]2+ and [2]2+ are worse Lewis acids than mostPd complexes. Because a charge is formally transferred to the π-system, they might be better described as monocationic on Pd. However, through C–N cleavage, the charge can be returned to Pd. So, these apparently poor Lewis acids may interconvert with a more Lewis acidic state (which should be comparable to other dicationic Pd). Thus, [1]2+and [2]2+could promote catalytic transformations that are specific to highly Lewis acidic dicationic Pd. A class of olefin activations unique to dicationic Pd involve generating β-carbonium character through olefin coordination and slippage (eq. 6).

[0290] Sen hasand has tested manydicationic Pd(II) complexes as catalysts. In MeCN, the fastest catalyst was the solvated dication,Attorney Docket No. 0073605-001022 [Pd(MeCN)4]2+; rates of reaction slow as the catalyst is increasingly substituted with Lewis basic ligands.3a, 3b

[0291] The present study tested for the presence of a Lewis acidic state by comparing theshapeshifting complexes [1]2+and [2]2+to other Pd complexes: [Pd(MeCN)4]2+, [Pd(bc)(MeCN)2]2+, [Pd(bpy)(MeCN)2]2+, and [Pd(PPh3)2(MeCN)2]2+(bc = bathocuproine; bpy = 2,2’-bipyridine). [4]2+, which bears model ligand L3 (eq. 7), was also synthesized.

[0292] The model ligand L3 lacks an olefin and can only bind through the pyrimidine N; [4]2+therefore represents a crude model for the Lewis acidic state of [1]2+or [2]2+.

[0293] Because all the tested complexes have MeCN ligands, the nitrile stretching frequences(νC≡N) can be used as an additional tool for ordering Lewis acidity (beyond catalytic activity).23Drago has noted that νC≡Nincreases (relative to free MeCN) upon coordination to a Lewis acidic metal; the magnitude of this shift depends on Lewis acidity.24The observed νC≡Nare reported in FIG. 6, legend.

[0294] As expected, νC≡N appears at the highest wavenumber for [Pd(MeCN)4]2+ (2354 cm-1);those of complexes [1]2+and [2]2+appear below all the benchmark complexes (2324 and 2323 cm-1). A similar νC≡N was observed with the bona fide monocation [Pd(bpy)(MeCN)(Me)]+(2323 cm-1). These observations further support that [1]2+and [2]2+are charge separated.

[0295] When the catalysts are used to isomerize 1-hexene in CD3CN, the relative rates ofreaction are [Pd(MeCN)4]2+> [4]2+> [2]2+> [1]2+> [Pd(bc)(MeCN)2]2+> [Pd(bpy)(MeCN)2]2+> [Pd(PPh3)2(MeCN)2]2+(see FIG. 6). The bis-phosphine only converts 3% of the substrate after 24 hours. Catalytic activity trends with νC≡Nexcept for [1]2+and [2]2+(which are faster than would be expected).25

[0296] The geometric isomerization of cis-stilbene to trans-stilbene was also tested. This olefinlacks allylic hydrogens, so the consensus mechanism involves: (1) substrate coordination, (2) olefin slippage – making C–C rotation more facile by imparting more single-bond character, and (3)Attorney Docket No. 0073605-001022 product dissociation.5cThe geometric isomerization of cis-stilbene occurs with relative rates [2]2+> [1]2+> [Pd(MeCN)4]2+> [4]2+in MeCN (FIG. 7) – though the differences in rate are marginal.26Discussion: Advantages from “Masking” a Reactive State

[0297] The stoichiometric and catalytic results can be explained by [1]2+ and [2]2+ accessing amore electrophilic state through C–N bond cleavage. Structurally, these states likely resemble [2– PPh3]2+; electronically they might resemble model complex [4]2+.27

[0298] Because these ligands “mask” Lewis acidity, the concentration for the electrophilic statehas been suppressed. These concentration effects would account for the order of activity in the isomerization of 1-hexene (see Kinetic Model 1 described below in this disclosure).

[0299] In the geometric isomerization of cis-stilbene to trans-stilbene, [2]2+ and [1]2+ are fasterthan structurally static electrophiles. Under certain circumstances, the shapeshifting catalysts described herein can offer kinetic advantages.

[0300] The energy for all presumed intermediates in the isomerization of cis-stilbene to trans-stilbene were computed to identify such circumstances. The minima were identified on the potential energy surface featuring the reactant / product with the catalyst [1]2+in both (a) the κ1-alkyl mode(A’, B’, and C’; see FIG. 8) and (b) the κ2-pyrimidine / olefin mode (A’’, B’’, and C’’; FIG. 8). Fromthe substrate-bound states, B’ and B’’, a transition state (TS) search was performed by inputting guess structures gathered from a scan of the H–C=C–H dihedral angle (of stilbene). The κ1-alkyl(B’) did not converge on any TS despite exhaustive search efforts. A transition state was identifiedfrom the κ2-pyrimidine / olefin (TS’’ is +15.7 kcal mol-1 from B’’, see FIG 60). These findings furthersuggest that C–N bond cleavage must occur before the Pd is electrophilic enough to activate the olefin. An analogous thermodynamic landscape was computed using [2]2+(see FIG. 60, in this case TS’’ is +16.0 kcal mol-1from the corresponding B’).

[0301] Assuming the olefin only isomerizes through B’’ (B’’ → TS’’ → C’’), the rate of thecatalytic reaction will be accelerated by any more rapid means of generating B’’.28For example, if substrate association has been accelerated by introducing the “masking” κ1-alkyl state,29then the shapeshifting system would exhibit a rate acceleration like that which we have observed (relative to a structurally static case). A derivation can be found in Kinetic Model 1 and 2, as described below in this disclosure.

[0302] The rate accelerations and decelerations we have observed between [1]2+ / [2]2+ and otherdications (like [Pd(MeCN)4]2+) have been modest. However, if the introduced state (the “masking”Attorney Docket No. 0073605-001022 κ1–alkyl) greatly accelerates a step that was slow for the strongly Lewis acidic masked” state, then larger kinetic differences are to be expected (see Kinetic Model 2 described below). For example, olefinic substrates bearing polar functional groups are problematic for Lewis acidic catalysts. Those polar functional groups compete with the olefin (to bind) and are slow to dissociate. Slow, rate determining dissociations prevent processing of polar substrates. Because the ligands described herein install a more nucleophilic state into the catalyst, these dissociative steps would likely be accelerated.

[0303] Several substrates bearing polar functional groups were treated with catalytic quantitiesof [1]2+, [2]2+, [Pd(MeCN)4]2+, and [4]2+(Table 1). Table 1. Polar substrates isomerized by Pd complexes.eAttorney Docket No. 0073605-001022

[0304] Neither [Pd(MeCN)4]2+ nor [4]2+ effectively process these substrates; the “masked”electrophiles [1]2+and [2]2+are generally effective. For each substrate, the same patterns are observed in the time course data (collected by1H NMR). For example, hex-5-ene-2-one chelates to [Pd(MeCN)4]2+and the catalyst decomposes within the first 136 minutes to a Pd mirror. In contrast, both [1]2+and [2]2+process this substrate throughout the entire time course of 9000 minutes (see FIG. 9). Unlike in previously discussed comparisons, the more hindered catalyst [2]2+is substantiallyAttorney Docket No. 0073605-001022 faster than [1]2+. This observation is what would be expected for more rapid ligand dynamics (see Kinetic Model 3 described below).

[0305] Catalyst decomposition prevents systems like [Pd(MeCN)4]2+ and [4]2+ from fullyconverting the substrate. The shapeshifting systems are active over a longer period, suggesting that the ligands also somehow protect dicationic Pd from decomposition. Even with the slowest / most challenging substrate attempted – dimethyl maleate (an electron deficient olefin bearing chelating Lewis basic functionality) –substantial conversion was observed prior to catalyst decomposition (reaction occurs over 600 hours, see FIG. 39).

[0306] To better assess catalyst lifetime, the reactions were repeated with the polar substrates inexorbitant excess. These reactions were performed in MeNO2to make the experimental timescale practical (reaction rates are faster in MeNO2relative to MeCN).3cThe reactions were sampled until no change was detectable for the substrate-to-product ratio (by1H NMR). If at a given substrate concentration, a catalyst achieved complete conversion, an additional experiment was performed where the substrate concentration was increased by an order of magnitude (see FIG. 10). For example, using hex-5-ene-2-one as substrate, [1]2+and [2]2+fully convert 1 × 104and 1 × 105equivalents of substrate. But with 1 × 106equivalents of that substrate, a 19% conversion was observed. This observation corresponds to a turnover number of 1.9 × 105. Product was not detectable in analogous experiments using [Pd(MeCN)4]2+or [4]2+. So, the shapeshifting catalysts outperform the structurally static counterparts by five orders of magnitude. Similar results were obtained using other polar substrates (see FIG. 58). Conclusion

[0307] The properties for Lewis acidic transition metal complexes make them useful foractivating olefinic substrates. However, when used as catalysts, those same properties predispose these compounds to inhibition and / or death (e.g., through irreversible substrate coordination). This exemplary study illustrates an approach that reversibly stabilizes charge – by “masking” a Lewis acidic Pd(II) dication. The ligands L1 and L2 transfer charge through the C–N bond form formation, delocalizing the dication into the aromatic 14 electron π-system. Stoichiometric experiments imply that the charge can be relocalized onto Pd through C–N bond cleavage (especially when exogenous ligands and / or substrates are added to solution). Access to a more Lewis acidic state is further suggested by catalytic performances, where [1]2+and [2]2+react similarly to benchmark Pd dications (e.g., [Pd(MeCN)4]2+). The “shapeshifting” ligands install a second, more nucleophilic state into anAttorney Docket No. 0073605-001022electrophilic catalyst. This feature likely accounts for why [1]2+ and [2]2+ effectively processsubstrates bearing polar functional groups.

[0308] For a shapeshifting catalyst, every elementary step of a catalytic cycle can occur fromeither of the two states.30The Curtin Hammett principle31indicates that the faster reaction will be more kinetically relevant. Two state catalysts may mitigate the unattractive properties that are intrinsic to either state.

[0309] Example 1 References

[0310] 1. (a) Hahn, C.; Vitagliano, A.; Giordano, F.; Taube, R., Coordination of Olefins and N-Donor Ligands at the Fragment [2,6-Bis((diphenylphosphino)methyl)pyridine]- palladium(II). Synthesis, Structure, and Amination of the New Dicationic Complexes [Pd(PNP)(CH2CHR)](BF4)2(R = H, Ph). Organometallics 1998, 17 (10), 2060-2066. (b) Chang, T. C. T.; Foxman, B. M.; Rosenblum, M.; Stockman, C., Reactivity of distorted C5H5Fe(CO)2(olefin) cations toward nucleophilic attack. J. Am. Chem. Soc. 1981, 103 (24), 7361-7362. (c) Fürstner, A.; Davies, P. W., Catalytic Carbophilic Activation: Catalysis by Platinum and Gold π Acids. Angew. Chem. Int. Ed. 2007, 46 (19), 3410-3449. (d) Eisenstein, O.; Hoffmann, R., Transition-metal complexed olefins: how their reactivity toward a nucleophile relates to their electronic structure. J. Am. Chem. Soc. 1981, 103 (15), 4308-4320.

[0311] 2. (a) Kurosawa, H.; Ikeda, I., Recent developments in the chemistry of olefin complexesof palladium and platinum: Some novel findings as well as elaborate extensions. J. Organomet. Chem.1992, 428 (1), 289-301. (b) Pi-Complexes. In The Organometallic Chemistry of the Transition Metals, 2014; pp 134-162(c) Sakaki, S.; Maruta, K.; Ohkubo, K., Ab initio MO study of palladium-assisted nucleophilic attack on a coordinated olefin: semiquantitative understanding of the reaction and the mechanism of palladium acceleration. Inorg. Chem. 1987, 26 (15), 2499-2505. (d) Felix, R. J.; Munro-Leighton, C.; Gagné, M. R., Electrophilic Pt(II) Complexes: Precision Instruments for the Initiation of Transformations Mediated by the Cation–Olefin Reaction. Acc. Chem. Res. 2014, 47 (8), 2319-2331. (e) Chianese, A. R.; Lee, S. J.; Gagné, M. R., Electrophilic Activation of Alkenes by Platinum(II): So Much More Than a Slow Version of Palladium(II). Angew. Chem. Int. Ed. 2007, 46 (22), 4042-4059. (f) Cameron, A. D.; Smith Jr, V. H.; Baird, M. C., On the mechanism of activation of coordinated olefins toward nucleophilic attack. Int. J. Quantum Chem 1986, 30 (S20), 657-663.Attorney Docket No. 0073605-001022

[0312] 3. (a) Sen, A.; Lai, T.-W., Catalysis by solvated transition-metal cations. Novel catalytictransformations of alkenes by tetrakis(acetonitrile)palladium ditetrafluoroborate. Evidence for the formation of incipient carbonium ions as intermediates. J. Am. Chem. Soc. 1981, 103 (15), 4627- 4629. (b) Sen, A.; Lai, T. W., Mechanism of palladium(II)-catalyzed carbon-carbon double bond isomerization in olefins. Inorg. Chem. 1984, 23 (20), 3257-3258. (c) Sen, A.; Lai, T.-W.; Thomas, R. R., Reactions of electrophilic transition metal cations with olefins and small ring compounds. Rearrangements and polymerizations. J. Organomet. Chem. 1988, 358 (1), 567-588.

[0313] 4. (a) Koh, J. H.; Mascarenhas, C.; Gagné, M. R., Pd(II)-Catalyzed cyclogeneration ofcarbocations: subsequent rearrangement and trapping under oxidative conditions. Tetrahedron 2004, 60 (34), 7405-7410. (b) Zhang, J.; Vaidya, T.; Brennessel, W. W.; Frontier, A. J.; Eisenberg, R., Dicationic Palladium(II) Complexes as Active Lewis Acid Catalysts for Polarized Nazarov Cyclization. Organometallics 2010, 29 (15), 3341-3349. (c) Mikami, K.; Hatano, M.; Akiyama, K., Active Pd(II) Complexes as Either Lewis Acid Catalysts or Transition Metal Catalysts. In Palladium in Organic Synthesis: Tsuji, J., Ed. Springer Berlin Heidelberg: Berlin, Heidelberg, 2005; pp 279- 321(d) Asao, N.; Nogami, T.; Takahashi, K.; Yamamoto, Y., Pd(II) Acts Simultaneously as a Lewis Acid and as a Transition-Metal Catalyst:  Synthesis of Cyclic Alkenyl Ethers from Acetylenic Aldehydes. J. Am. Chem. Soc. 2002, 124 (5), 764-765. (e) Rach, S. F.; Kühn, F. E., Nitrile Ligated Transition Metal Complexes with Weakly Coordinating Counteranions and Their Catalytic Applications. Chem. Rev. 2009, 109 (5), 2061-2080.

[0314] 5. (a) Ponec, R.; Řeřicha, R., Theoretical study of the catalytic activity of platinum(II)and palladium(II) complexes in cis-trans isomerisations of alkenes. J. Organomet. Chem. 1988, 341 (1), 549-557. (b) Camp, A. M.; Kita, M. R.; Blackburn, P. T.; Dodge, H. M.; Chen, C.-H.; Miller, A. J. M., Selecting Double Bond Positions with a Single Cation-Responsive Iridium Olefin Isomerization Catalyst. J. Am. Chem. Soc. 2021, 143 (7), 2792-2800. (c) Farquhar, A. H.; Gardner, K. E.; Acosta-Calle, S.; Camp, A. M.; Chen, C.-H.; Miller, A. J. M., Cation-Controlled Olefin Isomerization Catalysis with Palladium Pincer Complexes. Organometallics 2022, 41 (22), 3366- 3372.

[0315] 6. (a) Suslov, D. S.; Bykov, M. V.; Abramov, P. A.; Pahomova, M. V.; Ushakov, I. A.;Voronov, V. K.; Tkach, V. S., [Pd(acac)(MeCN)2]BF4: air-tolerant, activator-free catalyst for alkene dimerization and polymerization. RSC Advances 2015, 5 (126), 104467-104471. (b) Hahn, C.; Cucciolito, M. E.; Vitagliano, A., Coordinated Olefins as Incipient Carbocations:  CatalyticAttorney Docket No. 0073605-001022 Codimerization of Ethylene and Internal Olefins by a Dicationic Pt(II)−Ethylene Complex. J. Am. Chem. Soc. 2002, 124 (31), 9038-9039. (c) Mecking, S., Cationic nickel and palladium complexes with bidentate ligands for the C–C linkage of olefins. Coord. Chem. Rev. 2000, 203 (1), 325-351. (d) Yruegas, S.; Paccagnini, M.; Ho, S. C.; Sattler, A.; Chirik, P. J., Nickel-Catalyzed Dimerization of Di- and Trisubstituted Olefins. Organometallics 2022, 41 (15), 2059-2066. (e) Dong, Z.; Ren, Z.; Thompson, S. J.; Xu, Y.; Dong, G., Transition-Metal-Catalyzed C–H Alkylation Using Alkenes. Chem. Rev. 2017, 117 (13), 9333-9403.

[0316] 7. Dénès, F.; Pérez-Luna, A.; Chemla, F., Addition of Metal Enolate Derivatives toUnactivated Carbon−Carbon Multiple Bonds. Chem. Rev. 2010, 110 (4), 2366-2447.

[0317] 8. (a) Sen, A., New olefin polymerization and copolymerization catalysts. Effect ofcoordinating functionalities. 2001, 73 (2), 251-254. (b) Mecking, S.; Johnson, L. K.; Wang, L.; Brookhart, M., Mechanistic Studies of the Palladium-Catalyzed Copolymerization of Ethylene and α-Olefins with Methyl Acrylate. J. Am. Chem. Soc. 1998, 120 (5), 888-899. (c) Jiang, Z.; Sen, A., Tailored cationic palladium(II) compounds as catalysts for highly selective linear dimerization of styrene and linear polymerization of p-divinylbenzene. J. Am. Chem. Soc. 1990, 112 (26), 9655- 9657.

[0318] 9. Nakamura, A.; Anselment, T. M. J.; Claverie, J.; Goodall, B.; Jordan, R. F.; Mecking,S.; Rieger, B.; Sen, A.; van Leeuwen, P. W. N. M.; Nozaki, K., Ortho-Phosphinobenzenesulfonate: A Superb Ligand for Palladium-Catalyzed Coordination–Insertion Copolymerization of Polar Vinyl Monomers. Acc. Chem. Res. 2013, 46 (7), 1438-1449.

[0319] 10. (a) Chen, C., Designing catalysts for olefin polymerization and copolymerization:beyond electronic and steric tuning. Nature Reviews Chemistry 2018, 2 (5), 6-14. (b) Williams, B. S.; Leatherman, M. D.; White, P. S.; Brookhart, M., Reactions of Vinyl Acetate and Vinyl Trifluoroacetate with Cationic Diimine Pd(II) and Ni(II) Alkyl Complexes:  Identification of Problems Connected with Copolymerizations of These Monomers with Ethylene. J. Am. Chem. Soc. 2005, 127 (14), 5132-5146. (c) Paulson, E. R.; Moore, C. E.; Rheingold, A. L.; Pullman, D. P.; Sindewald, R. W.; Cooksy, A. L.; Grotjahn, D. B., Dynamic π-Bonding of Imidazolyl Substituent in a Formally 16-Electron Cp*Ru(κ2-P,N)+ Catalyst Allows Dramatic Rate Increases in (E)-Selective Monoisomerization of Alkenes. ACS Catalysis 2019, 9 (8), 7217-7231. (d) Paulson, E. R.; Delgado, E., III; Cooksy, A. L.; Grotjahn, D. B., Catalyst versus Substrate Control of Forming (E)-2-AlkenesAttorney Docket No. 0073605-001022 from 1-Alkenes Using Bifunctional Ruthenium Catalysts. Organic Process Research & Development 2018, 22 (12), 1672-1682.

[0320] 11. (a) Zhao, M.; Chen, C., Accessing Multiple Catalytically Active States in Redox-Controlled Olefin Polymerization. ACS Catalysis 2017, 7 (11), 7490-7494. (b) Ríos, P.; Rodríguez, A.; Conejero, S., Enhancing the catalytic properties of well-defined electrophilic platinum complexes. Chem. Commun. 2020, 56 (40), 5333-5349.

[0321] 12. (a) Anticipating that cyclization includes charge transfer, we incorporated thepyrimidine into a larger 14 electron π system. Related references:. (b) Panunzi, A.; De Renzi, A.; Palumbo, R.; Paiaro, G., Addition reactions on coordinated olefinic ligands. II. Reaction between amines and monoolefins coordinated in cis-dichloro(olefin) (tert-phosphine)platinum(II) complexes. J. Am. Chem. Soc. 1969, 91 (14), 3879-3883. (c) Panunzi, A.; De Renzi, A.; Paiaro, G., Addition reactions on coordinated olefinic ligands. III. trans. Addition of a nucleophile to a platinum(II) coordinated simple olefin. J. Am. Chem. Soc. 1970, 92 (11), 3488-3489.

[0322] 13. (a) Hahn, C.; Morvillo, P.; Vitagliano, A., Olefins Coordinated at a HighlyElectrophilic Site − Dicationic Palladium(II) Complexes and Their Equilibrium Reactions with Nucleophiles. Eur. J. Inorg. Chem. 2001, 2001 (2), 419-429. (b) White, P. B.; Stahl, S. S., Reversible Alkene Insertion into the Pd–N Bond of Pd(II)-Sulfonamidates and Implications for Catalytic Amidation Reactions. J. Am. Chem. Soc. 2011, 133 (46), 18594-18597. (c) Kaplan, P. D.; Schmidt, P.; Orchin, M., Nuclear Magnetic Resonance Evidence for π → σ Ligand Conversion in Platinum(II) Complexes. J. Am. Chem. Soc. 1968, 90 (15), 4175-4176. (d) Senn, H. M.; Blöchl, P. E.; Togni, A., Toward an Alkene Hydroamination Catalyst:  Static and Dynamic ab Initio DFT Studies. J. Am. Chem. Soc. 2000, 122 (17), 4098-4107. (e) Åkermark, B.; Bäckvall, J. E.; Hegedus, L. S.; Zetterberg, K.; Siirala-Hansén, K.; Sjöberg, K., Palladium-promoted addition of amines to isolated double bonds. J. Organomet. Chem. 1974, 72 (1), 127-138. (f) Green, M.; Sarhan, J. K. K.; Al-Najjar, I. M., Neighboring group effects on the stability of azaplatinacyclobutane rings in (2- aminoethyl)platinum(II) compounds. Organometallics 1984, 3 (4), 520-524. (g) Pryadun, R.; Sukumaran, D.; Bogadi, R.; Atwood, J. D., Amine Attack on Coordinated Alkenes:  An Interconversion from Anti-Markovnikoff to Markovnikoff Products. J. Am. Chem. Soc. 2004, 126 (39), 12414-12420.

[0323] 14. Bismillah, A. N.; Chapin, B. M.; Hussein, B. A.; McGonigal, P. R., Shapeshiftingmolecules: the story so far and the shape of things to come. Chemical Science 2020, 11 (2), 324-332.Attorney Docket No. 0073605-001022

[0324] 15. (a) Yang, Y.-l.; Kou, Y., Determination of the Lewis acidity of ionic liquids bymeans of an IR spectroscopic probe. Chem. Commun. 2004, (2), 226-227. (b) Parry, E. P., An infrared study of pyridine adsorbed on acidic solids. Characterization of surface acidity. J. Catal. 1963, 2 (5), 371-379. (c) Balaban, A. T.; Mateescu, G. D.; Elian, M., Infra-red absorption spectra of pyrylium salts. Tetrahedron 1962, 18 (10), 1083-1094.

[0325] 16. Greenwood, N. N.; Wade, K., 232. Complexes of boron trichloride with pyridine andpiperidine. Journal of the Chemical Society (Resumed) 1960, (0), 1130-1141.

[0326] 17. Adamo, C.; Barone, V., Toward reliable density functional methods withoutadjustable parameters: The PBE0 model. The Journal of Chemical Physics 1999, 110 (13), 6158- 6170.

[0327] 18. (a) Weigend, F.; Ahlrichs, R., Balanced basis sets of split valence, triple zeta valenceand quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. Physical Chemistry Chemical Physics 2005, 7 (18), 3297-3305. (b) Andrae, D.; Huermann, U.; Dolg, M.; Stoll, H.; Preu, H. L., Energy-adjustedab initio pseudopotentials for the second and third row transition elements. Theoretica chimica acta 1990, 77, 123-141.

[0328] 19. Miertuš, S.; Scrocco, E.; Tomasi, J., Electrostatic interaction of a solute with acontinuum. A direct utilizaion of AB initio molecular potentials for the prevision of solvent effects. Chem. Phys. 1981, 55 (1), 117-129.

[0329] 20. Neuhaus, D.; Williamson, M. P. The Nuclear Overhauser Effect in Structural andConformational Analysis, 2nd ed.; Wiley-VCH: New York, 2000; pp 185− 187.

[0330] 21. By DFT, the drawn κ2-pyrimidine / olefin bearing two MeCN ligands was found to bemore stable than either the κ1-olefin or the κ1-pyrimidine isomer bearing three MeCN ligands.

[0331] 22. For [2]2+, the κ2-isomer was predicted to be more stable by 0.63 kcal mol-1.However, given the proximity to thermoneutrality, identifying the more stable isomer by DFT may be impractical. Experimentally, the1H NMR are consistent with a κ1-alkyl, even at -35 °C (CD3CN, no signs of coalescence). .

[0332] 23. (a) Henneike, H. F., Jr.; Drago, R. S., Comparison of the donor properties ofdimethylcyanamide and acetonitrile. Inorg. Chem. 1968, 7 (9), 1908-1915. (b) N. Storhoff, B.; C. Lewis Jr, H., Organonitrile complexes of transition metals. Coord. Chem. Rev. 1977, 23 (1), 1-29.

[0333] 24. (a) Reedijk, J.; Zuur, A. P.; Groeneveld, W. L., Complexes with ligands containingnitrile groups. Part III. Infrared spectra of coordinated methyl cyanide. Recl. Trav. Chim. Pays-BasAttorney Docket No. 0073605-001022 1967, 86 (10), 1127-1137. (b) Purcell, K. F., .sigma.- and .pi.-Bonding effects in the coordination of the cyano group. J. Am. Chem. Soc. 1967, 89 (24), 6139-6143. (c) Wayland, B. B.; Schramm, R. F., Cationic and neutral chloride complexes of palladium(II) with the nonaqueous solvent donors acetonitrile, dimethyl sulfoxide, and a series of amides. Mixed sulfur and oxygen coordination sites in a dimethyl sulfoxide complex. Inorg. Chem. 1969, 8 (4), 971-976. (d) Purcell, K. F.; Drago, R. S., Studies of the Bonding in Acetonitrile Adducts1. J. Am. Chem. Soc. 1966, 88 (5), 919-924. (e) These changes reflect strengthening of σC–Nand σC–C(which gain more s-orbital character in response to generating a M–N bond). Other effects – backbonding, kinematic coupling (Pd–N^C–CH3), and Fermi resonance – are comparatively small.

[0334] 25. The catalytic activities for [1]2+ and [2]2+ might also be compared to[Pd(L)(MeCN)(Me)]+(L = bc, bpy), where olefin isomerization is competitive with polymerization through olefin insertion. No insertion reactions were observed for [1]2+and [2]2+, further reiterating their anomalous catalytic behavior. See (a) G. R. Jones, H. E. Basbug Alhan, L. J. Karas, J. I. Wu, E. Harth, Switching the reactivity of palladium diimines with “ancillary” ligand to select between olefin polymerization, branching regulation, or olefin isomerization. Angew. Chem. Int. Ed. 2021, 60, 1635; (b) D. Nguyen, S. Wang, L. C. Grabow, E. Harth, Deciphering the Olefin Isomerization- Polymerization Paradox of Palladium(II) Diimine Catalysts: Discovery of Simultaneous and Independent Pathways of Olefin Isomerization and Living Polymerization. J. Am. Chem. Soc. 2023, 145, 9755.

[0335] 26. The other Pd dications [Pd(N–N)(MeCN)2]2+ (N–N = bc, bpy) and[Pd(PPh3)2(MeCN)2]2+were not active in this transformation.

[0336] 27. It is anticipated that the olefin arms for [κ2-1]2+ and [κ2-2]2+ are less nucleophilicthan the nitrile ligand of [4]2+(consider the typical position for πC=Cvs the nitrile lone pair).

[0337] 28. A description of when a rate acceleration should be expected based on theinstallation of a new state can be found in the supporting information "Discussion of postulated Curtin-Hammett derived rate acceleration." That discussion also includes several kinetic models that illustrate expected catalytic rate accelerations.

[0338] 29. The computations predict that the association of cis–stilbene to the electrophilic κ2-pyrimidine / olefin state (e.g., [κ2–1]2+) is more endergonic than association to the corresponding κ1- alkyl (e.g., [κ1–1]2+).Attorney Docket No. 0073605-001022

[0339] 30. (a) General reviews on two-state catalysis (b-d); other examples of two statecatalysis include: hemilability (e-g); metal-ligand cooperativity (h-k); metal / ligand proton tautomerism (l-o); other tautomerisms (p-s), structurally dynamic ligands (t,u), and spin acceleration (v). Further related work involves conformational gating (w,x). (b) Crabtree, R. H., Multifunctional ligands in transition metal catalysis. New J. Chem. 2011, 35 (1), 18-23. (c) Annibale, V. T.; Song, D., Multidentate actor ligands as versatile platforms for small molecule activation and catalysis. RSC Advances 2013, 3 (29), 11432-11449. (d) Blacquiere, J. M., Structurally-Responsive Ligands for High-Performance Catalysts. ACS Catalysis 2021, 11 (9), 5416-5437. (e) Miller, E. M.; Shaw, B. L., Kinetic and other studies on oxidative addition reactions of iridium phosphine complexes of the type trans-[IrCl(CO)(PMe2R)2](R = Ph, o-MeO·C6H4, or p-MeO·C6H4). J. Chem. Soc., Dalton Trans. 1974, (5), 480-485. (f) Jeffrey, J. C.; Rauchfuss, T. B., Metal complexes of hemilabile ligands. Reactivity and structure of dichlorobis(o-(diphenylphosphino)anisole)ruthenium(II). Inorg. Chem. 1979, 18 (10), 2658-2666. (g) Adams, G. M.; Weller, A. S., POP-type ligands: Variable coordination and hemilabile behaviour. Coord. Chem. Rev. 2018, 355, 150-172. (h) Khusnutdinova, J. R.; Milstein, D., Metal–Ligand Cooperation. Angew. Chem. Int. Ed. 2015, 54 (42), 12236-12273. (i) Verhoeven, D. G. A.; Moret, M.-E., Metal–ligand cooperation at tethered π-ligands. Dalton Transactions 2016, 45 (40), 15762-15778. (j) Higashi, T.; Kusumoto, S.; Nozaki, K., Cleavage of Si–H, B–H, and C–H Bonds by Metal–Ligand Cooperation. Chem. Rev. 2019, 119 (18), 10393- 10402. (k) Habraken, E. R. M.; Jupp, A. R.; Brands, M. B.; Nieger, M.; Ehlers, A. W.; Slootweg, J. C., Parallels between Metal-Ligand Cooperativity and Frustrated Lewis Pairs. Eur. J. Inorg. Chem. 2019, 2019 (19), 2436-2442. (l) Quintana, L. M. A.; Johnson, S. I.; Corona, S. L.; Villatoro, W.; Goddard, W. A.; Takase, M. K.; VanderVelde, D. G.; Winkler, J. R.; Gray, H. B.; Blakemore, J. D., Proton–hydride tautomerism in hydrogen evolution catalysis. Proceedings of the National Academy of Sciences 2016, 113 (23), 6409-6414. (m) Pal, S.; Kusumoto, S.; Nozaki, K., Dehydrogenation of Dimethylamine–Borane Catalyzed by Half-Sandwich Ir and Rh Complexes: Mechanism and the Role of Cp* Noninnocence. Organometallics 2018, 37 (6), 906-914. (n) Kuo, J. L.; Goldberg, K. I., Metal / Ligand Proton Tautomerism Facilitates Dinuclear H2Reductive Elimination. J. Am. Chem. Soc. 2020, 142 (51), 21439-21449. (o) Bhatti, T. M.; Kumar, A.; Parihar, A.; Moncy, H. K.; Emge, T. J.; Waldie, K. M.; Hasanayn, F.; Goldman, A. S., Metal–Ligand Proton Tautomerism, Electron Transfer, and C(sp3)–H Activation by a 4-Pyridinyl-Pincer Iridium Hydride Complex. J. Am. Chem. Soc. 2023, 145 (33), 18296-18306. (p) Dugan, T. R.; Sun, X.; Rybak-Akimova, E. V.; Olatunji-Ojo,Attorney Docket No. 0073605-001022 O.; Cundari, T. R.; Holland, P. L., A Masked Two-Coordinate Cobalt(I) Complex That Activates C– F Bonds. J. Am. Chem. Soc. 2011, 133 (32), 12418-12421. (q) Gisewhite, D. R.; Yang, J.; Williams, B. R.; Esmail, A.; Stein, B.; Kirk, M. L.; Burgmayer, S. J. N., Implications of Pyran Cyclization and Pterin Conformation on Oxidized Forms of the Molybdenum Cofactor. J. Am. Chem. Soc. 2018, 140 (40), 12808-12818. (r)Li, Z.; Wang, Z.; Chekshin, N.; Qian, S.; Qiao, J. X.; Cheng, P. T.; Yeung, K.- S.; Ewing, W. R.; Yu, J.-Q., A tautomeric ligand enables directed C‒H hydroxylation with molecular oxygen. Science 2021, 372 (6549), 1452-1457. (s) Race, J. J.; Albrecht, M., Pyridylidene Amines and Amides: Donor-Flexible Ligands for Catalysis. ACS Catalysis 2023, 13 (14), 9891-9904. (t) Jackman, K. M. K.; Bridge, B. J.; Sauvé, E. R.; Rowley, C. N.; Zheng, C. H. M.; Stubbs, J. M.; Boyle, P. D.; Blacquiere, J. M., C(sp3)–C(sp3) Coupling with a Pd(II) Complex Bearing a Structurally Responsive Ligand. Organometallics 2019, 38 (8), 1677-1681. (u) Jackman, K. M. K.; Liang, G.; Boyle, P. D.; Zimmerman, P. M.; Blacquiere, J. M., Changes in ligand coordination mode induce bimetallic C–C coupling pathways. Dalton Transactions 2022, 51 (10), 3977-3991. (v) Holland, P. L., Distinctive Reaction Pathways at Base Metals in High-Spin Organometallic Catalysts. Acc. Chem. Res. 2015, 48 (6), 1696-1702. (w) Charette, B. J.; King, S. R.; Chen, J.; Holm, A. R.; Malme, J. T.; Cook, R. D.; Schaller, R. D.; Jackson, N. E.; Olshansky, L., Excited State Dynamics of a Conformationally Fluxional Copper Coordination Complex. The Journal of Physical Chemistry A 2023, 127 (37), 7747-7755. (x) Griffin, P. J.; Olshansky, L., Rapid Electron Transfer Self-Exchange in Conformationally Dynamic Copper Coordination Complexes. J. Am. Chem. Soc. 2023, 145 (37), 20158-20162.

[0340] 31. Seeman, J. I., Effect of conformational change on reactivity in organic chemistry.Evaluations, applications, and extensions of Curtin-Hammett Winstein-Holness kinetics. Chem. Rev. 1983, 83 (2), 83-134. Supporting Data for Example 1

[0341] Synthetic Procedures

[0342] Synthesis of SI1Attorney Docket No. 0073605-001022

[0343] Under N2, 3,3-dimethyl-1-butyne (3.12 mL, 25.38 mmol) was dissolved in 40 mL of dryTHF. Ethyl magnesium bromide (8.88 mL of 3.0 M in Et2O) was then added dropwise over a period of approximately 5 minutes. The resulting mixture was heated at 50 °C for two hours. 2- aminobenzonitrile (1.5 g, 12.6 mmol) was weighed in a vial, dissolved in ~2 mL of THF and added dropwise to the reaction mixture over a period of approximately 10 minutes. The vial was rinsed with an additional 1 mL of THF and added to the reaction mixture. The reaction changes from colorless to bright yellow and vigorous bubbling is observed. The mixture was heated at 50 °C until consumption of 2-aminobenzonitrile was observed by TLC (20% EtOAc / hexanes), approximately 20 hrs. The solution was then cooled to 0 °C and slowly acidified by the addition of 1 M H2SO4(~ 5 mL, until acidic to pH paper). The reaction was then stirred at room temperature for 3 days. During this time, the pH of the solution was monitored and additional H2SO4was added as necessary to maintain a pH of about 3-4. Next, the solution was neutralized by addition of saturated NaHCO3solution (approximately 20 mL). Vigorous stirring was necessary as this formed a biphasic mixture. This mixture was then transferred to a separatory funnel. The reaction flask was rinsed with EtOAc (3×), which was also transferred to the separatory funnel. The layers were separated and the aqueous phase was extracted with EtOAc (3×). The combined organic extracts were washed with saturated NaCl solution, dried over MgSO4and the solvent was evaporated. The resulting crude residue was purified via silica gel chromatography (10% EtOAc / hexanes – 30% EtOAc / hexanes) to yield SI1 as a yellow solid. Yields ranged from 33-72%.

[0344] Characterization of SI1

[0345] 1H NMR (500 MHz, CDCl3) δ 8.04 (dd, J = 8.0, 1.5 Hz, 1H, HB), 7.32 – 7.25 (m, 1H,HD), 6.68 (ddd, J = 8.0, 7.0, 1.0 Hz, 1H, HC), 6.62 (dd, J = 8.5, 1.0 Hz, 1H, HE), 6.29 (s, 2H, HF), 1.37 (s, 9H, HA). See FIG. 11A.

[0346] 13C{1H} NMR (126 MHz, CDCl3) δ 180.24, 151.04, 135.11, 134.73, 119.12, 116.80,116.12, 103.06, 78.46, 30.40, 28.13. See FIG. 11B.

[0347] HRMS (ESI-TOF) m / z: [M + H]+ Calcd for C13H17NO: 202.1232. Found: 202.1226.

[0348] FTIR (neat) cm-1: 3450 (br), 3341 (br), 1619 (s), 1584 (s), 1258 (s), 1232 (s).

[0349] Synthesis of SI2Attorney Docket No. 0073605-001022

[0350] 645 mg SI1 (3.22 mmol) was dissolved in 30 mL absolute ethanol. 0.37 mL hydrazinemonohydrate (6.44 mmol) was added dropwise and the mixture was refluxed under N2overnight. The solvent was then evaporated under reduced pressure and the crude residue was purified via silica gel chromatography (10% EtOAc / hexanes). SI2 was obtained as a pale yellow / green solid with yields ranging from 20-83%. In some instances, the crude reaction mixture was alternatively purified via recrystallization from minimal hot ethanol. Yields in this case ranged from 86-92%.

[0351] Characterization of SI2

[0352] 1H NMR (500 MHz, CDCl3) δ 7.41 (d, J = 8.0 Hz, 1H; HD), 7.10 (t, J = 8.0 Hz, 1H; HF),6.84 (t, J = 7.5 Hz, 1H; HE), 6.70 (d, J = 8.0 Hz, 1H, HG), 6.33 (s, 1H, HB), 1H; HHor HC;likely H-bonded), 1.33 (s, 9H; HA). See FIG. 11C.

[0353] 13C{1H} NMR (101 MHz, CDCl3) δ 161.87, 139.25, 136.27, 128.74, 123.80, 119.74,115.41, 96.02, 71.94, 32.38, 30.82. See FIG. 11D.

[0354] HRMS (ESI-TOF) m / z: [M + H]+ Calcd for C13H18N3: 216.1500. Found: 216.1495.

[0355] FTIR (neat) cm-1: 3368 (s), 2959 (m), 1614 (m), 1590 (m), 1489 (s), 1421 (m), 1360 (m),1238 (s), 1197 (m), 994 (m), 751 (vs).

[0356] Synthesis of L1

[0357] (EDC·HCl,0.751 mmol, 1.3 equiv.) and 4-dimethylaminopyridine (DMAP, 0.810 mmol, 1.4 equiv.) were dissolved in 15 mL dry DCM. The solution was cooled to 0°C, then 4-pentenoic acid (0.578 mmol, 1.0 equiv.) was added dropwise via syringe and the reaction mixture was stirred for five minutes. SI2 (0.691 mmol, 1.2 equiv.) was dissolved in 2 mL dry DCM and added dropwise to the reactionAttorney Docket No. 0073605-001022 mixture via syringe. The reaction was stirred at room temperature overnight and monitored via TLC (20% EtOAc / hexanes). A mixture of SI3 and L1 was typically observable by TLC. 1 M HCl was then added (approx. 5 drops, until acidic to pH paper) and the solution was stirred at room temperature overnight. SI3 was observed to convert to L1 under these conditions. The mixture was then partitioned with water and the resulting aqueous phase was extracted with DCM (3×). Combined DCM extracts were washed with saturated NaCl solution, dried over MgSO4and the solvent was evaporated. The crude residue was purified via silica gel chromatography (10% EtOAc / hexanes), and both SI3 and L1 were collected. Recovered SI3 was then dissolved in DCM and acidified with 1M HCl. After stirring at room temperature overnight, a clean conversion to L1 was generally observed by TLC. The mixture was then transferred to a separatory funnel and washed with 1 M NaHCO3solution (2×). The aqueous phase was extracted with DCM (3×), then the combined DCM extracts were washed with a saturated NaCl solution and dried over MgSO4. The solvent was evaporated and the crude residue was eluted from a plug of silica with a 1% EtOAc / hexanes solution. Overall, 143 mg L1 was obtained a colorless oil (83%).

[0358] Characterization of L1

[0359] 1H NMR (500 MHz, CD3CN) δ 8.10 (dd, J = 8.0, 1.5 Hz, 1H; HC), 7.84 (dd, J = 7.5, 1.0,1H; HF), 7.66 (ddd, J = 8.0, 7.0, 1.5 Hz, 1H; HD), 7.58 (ddd, J = 7.5, 7.0, 1.0 Hz, 1H; HE), 7.09 (s, 1H; HB), 6.06 (ddt, J = 17.0, 10.0, 6.5 Hz, 1H; HI), 5.16 (dd, J = 17.0, 2.0 Hz, 1H; HK), 5.03 (dd, J = 10.5, 1.5 Hz, 1H; HJ), 3.40 (m, 2H; HG), 2.78 (m, 2H; HH), 1.47 (s, 1H). See FIG. 11E.

[0360] 13C{1H} NMR (101 MHz, CD3CN) δ 166.75, 151.33, 140.51, 140.38, 138.68, 130.30,128.62, 127.93, 124.07, 120.39, 115.69, 96.17, 33.37, 32.65, 30.68, 30.58. See FIG. 11F.

[0361] HRMS (ESI-TOF) m / z: [M + H]+ Calcd for C18H21N3: 280.1813. Found: 280.1808.

[0362] FTIR (neat) cm-1: 3076 (w), 2961 (m), 1620 (s), 1546 (m), 1475 (m), 1385 (m), 1245(m), 912 (m), 754 (vs).

[0363] Synthesis of L2Attorney Docket No. 0073605-001022

[0364] L2 was synthesized using a procedure nearly identical to that of L1, usingEDC·HCl / DMAP to couple SI2 and (E)-5-(4-(tert-butyl)phenyl)pent-4-enoic acid. These procedures differed only in the final purification of L2. The crude product obtained from stirring purified SI4 in acidified DCM overnight was suspended in approximately 5 mL of MeOH and filtered through Celite®. The compound was then washed from the Celite with DCM and the solvent was evaporated. The resulting colorless powder was redissolved in minimal DCM (approximately 1 mL), layered with MeOH (approximately 12 mL) and the solvents were allowed to slowly mix in the freezer overnight. Colorless needles of L2 were obtained by filtering the mixture through a medium porosity frit and washing with minimal cold MeOH (3×). Overall yields ranged from 66-89%.

[0365] Characterization of L2

[0366] 1H NMR (500 MHz, CD2Cl2) δ 8.12 (dd, J = 8.0, 1.5* Hz, 1H), 7.98 (dd, J = 7.5, 1.0*Hz, 1H), 7.77 – 7.70 (ddd, J = 8.0, 7.0, 1.5, 1H), 7.65 (ddd, J = 7.5, 7.0, 1.0 Hz, 1H), 7.46 – 7.36 (m, 4H), 7.02 (s, 1H), 6.62 (d, J = 16.0 Hz, 1H), 6.52 (dt, J = 16.0, 6.5 Hz, 1H), 5.46 (s, 1H), 5.45 (s, 2H), 3.62 (dd, J = 8.5, 6.5 Hz, 2H), 3.04 (q, J = 7.5 Hz, 2H), 1.67 (s, 5H), 1.58 (s, 9H), 1.42 (s, 9H). (*implied) Assignments are depicted in FIG. 11G.

[0367] 13C{1H} NMR (126 MHz, CD2Cl2) δ 166.24, 151.03, 140.19, 139.87, 135.28, 130.67,129.51, 129.13, 128.27, 127.13, 126.01, 125.75, 123.32, 120.00, 95.22, 54.27, 54.06, 53.84, 53.62, 53.41, 34.76, 33.08, 32.89, 31.42, 30.65, 29.84. See FIG. 11H.

[0368] HRMS (ESI-TOF) m / z: [M + H]+ Calcd for C28H34N3: 412.2752. Found: 412.2746.

[0369] FTIR (neat) cm-1: 3040 (w), 2962 (s), 1670 (s), 1619 (s), 1591 (vs), 1544 (s), 1468 (s),1415 (m), 1295 (s), 967 (m), 800 (m), 759 (vs).

[0370] Synthesis of L3

[0371] EDC·HCl / DMAP to couple SI4 and pentanoic acid. L3 was isolated as a yellow oil in yields ranging from 51-76%.

[0372] Characterization of L3Attorney Docket No. 0073605-001022

[0373] 1H NMR (500 MHz, CD3CN) δ 8.07(dd, J = 7.5 Hz, 1H), 7.80 (dd, J = 8.0 Hz, 1H), 7.64(ddd, J = 8.0, 7.0, 1.5, 1H), 7.55 (ddd, J = 7.5, 7.0, 1.0, 1H), 7.04 (s, 1H), 3.27 (t, J = 7.5 Hz, 2H), 1.49 (m, 2H), 1.43 (s, 9H), 0.99 (t, J = 7.5 Hz, 3H). See FIG. 11I.

[0374] 13C{1H} NMR (126 MHz, CD3CN) δ 166.65, 152.22, 140.60, 140.38, 130.24, 128.57,127.80, 124.04, 120.37, 96.08, 33.37, 32.85, 30.70, 28.83, 23.13, 14.14. See FIG. 11J.

[0375] HRMS (ESI-TOF) m / z: [M + H]+ Calcd for C18H24N3: 282.1970. Found: 282.1966.

[0376] FTIR (neat) cm-1: 2958 (m), 1621 (s), 1546 (m), 1475 (m), 1385 (m), 1362 (m), 1245(m), 979 (w), 754 (vs).

[0377] Synthesis of [1][BF4]2

[0378] [Pd(MeCN)4]in 2 mL of acetonitrile insidean inert atmosphere glovebox. L1 (9.8 mg, 0.035 mmol) dissolved in 1.5 mL of acetonitrile was added dropwise over approximately 2 minutes. The resulting solution was stirred at room temperature for 30 minutes then stored at –25°C for an additional 30 minutes. Cold Et2O (approximately 12 mL) was added dropwise to the rapidly stirring solution until cloudiness persisted and a colorless precipitate began to form. The mixture was stored at –25 °C for 1 hour, then the colorless powder was collected on a medium porosity frit and washed 3× with minimal cold Et2O. The powder was dissolved in acetonitrile and recrystallized by layering with Et2O. Slow mixing of the solvents overnight at –25°C yielded 24 mg of [1][BF4]2as colorless needles (97%).

[0379] Characterization of [1][BF4]2

[0380] 1H NMR (500 MHz, CD3CN) δ 8.37 (dd, J = 8.0, 1.0 Hz, 1H), 8.05 – 7.98 (m, 2H), 7.91(ddd, J = 8.0, 7.0, 1.5 Hz, 1H), 7.52 (s, 1H), 5.42 (td, J = 9.0, 5.0 Hz, 1H), 4.14 – 4.05 (m, 1H), 3.99 – 3.92 (m, 1H), 3.00 – 2.91 (m, 1H), 2.78 – 2.72 (m, 1H), 2.48 – 2.41 (m, 2H), 1.47 (s, 9H). See FIG. 11K.

[0381] 13C{1H} NMR (101 MHz, CD3CN) δ 175.33, 158.58, 141.04, 133.12, 131.36, 129.97,126.40, 120.13, 119.30, 102.54, 70.24, 34.19, 30.67, 29.94, 28.56, 14.99. See FIG. 11L.

[0382] HRMS (ESI-TOF) m / z: [M – H – MECN]+ Calcd for C22H26N5Pd 466.1218; Found466.1226.Attorney Docket No. 0073605-001022

[0383] FTIR (neat) cm-1: 3144 (w), 2973 (m), 2324 (w), 2302 (w), 1634 (vs), 1607 (s), 1555(vs), 1255 (s), 1022 (s, br), 766 (vs).

[0384] Anal. Calcd. for [1][BF4]2 C24H30N6PdB2F8: C, 42.23; H, 4.43; N, 12.31. Found: C,25.19; H, 2.591; N, 7.180.*

[0385] *This compound was analyzed several times. While the analyses are close to “passing”,carbon content appears to be low, which could be due to formation of non-combusting Pd-carbides or sample decomposition. Given the ambiguity surrounding that compound, a wide variety of data were collected, including1H and13C NMR. The samples were first crystallized to yield X-ray quality crystals (and the structure of this compound was also resolved). IR and UV-visibledata were also collected. Using all these different techniques, no differences were discerned from sample-to-sample.

[0386] Synthesis of [2][BF4]2

[0387] [Pd(MeCN)4]in 3 mL of acetonitrile insidean inert atmosphere glovebox. L2 (14.8 mg, 0.036 mmol) dissolved in 3 mL of a 1:2 acetonitrile:Et2O solution was added dropwise over approximately 2 minutes. The resulting solution was stirred at room temperature for 30 minutes then stored at –25°C for an additional 30 minutes. Cold Et2O (approximately 12 mL) was added dropwise to the rapidly stirring solution, then pentane (approximately 1 ml) was added until cloudiness persisted and a pastel yellow precipitate began to form. The mixture was stored at –25°C for 1 hour, then the pastel yellow powder was collected on a frit and washed 3× with minimal cold Et2O. The powder was dissolved in acetonitrile andrecrystallized by slow vapor diffusion of Et2O into the solution to afford 27 mg of [2][BF4]2 as paleyellow needles (90%).

[0388] Characterization of [2][BF4]2

[0389] 1H NMR (500 MHz, CD3CN) δ 8.15 (d, J = 8.0, 1.0 Hz, 1H), 7.59 (ddd, J = 8.0, 6.5, 1.5Hz, 1H), 7.46 (s, 1H), 7.34 – 7.21 (m, 5H), 6.02 (dd, J = 10.5, 8.0 Hz, 1H), 4.27 – 4.15 (m, 1H), 4.09Attorney Docket No. 0073605-001022 – 4.00 (m, 1H), 3.62 (dd, J = 13.0, 8.0 Hz, 1H), 3.22 – 3.10 (m, 1H), 1.48 (s, 9H), 1.28 (s, 9H). See FIG. 11M.

[0390] 13C{1H} NMR (101 MHz, CD3CN) δ 175.53, 159.17, 152.10, 140.97, 137.78, 131.36,130.62, 130.03, 128.44, 127.63, 125.43, 120.86, 102.43, 73.31, 39.78, 35.46, 34.24, 31.10, 30.66, 30.16, 29.97. See FIG. 11N.

[0391] HRMS (ESI-TOF) m / z: [M–H–MECN]+ Calcd for C32H38N5Pd: 598.2162. Found:598.2169.

[0392] FTIR (neat) cm-1: 3129 (w), 2964 (m), 2323 (w), 2290 (w), 1635 (vs), 1557 (s), 1367(m), 1256 (s), 1023 (s, br), 765 (vs).

[0393] Anal. Calcd. for [4][BF4]2 C34H42B2F8N6Pd×MECN: C, 50.12; H, 5.20; N, 10.31. Found:C, 46.307; H, 4.604; N, 10.079.*

[0394] *This compound was analyzed several times. While the analyses are close to “passing”,the samples appear low in carbon. This observation could be due to formation of non-combusting Pd-carbides and / or sample decomposition during shipping. However, the samples used in this disclosure are first crystallized to yield X-ray quality crystals (and an X-ray structure was also resolved). The samples are then analyzed by1H and13C NMR, as well as IR and UV-Vis spectroscopies. Using all these different techniques, no differences were discerned from sample-to- sample.

[0395] Synthesis of 3

[0396] Pd(MeCN)of dichloromethane insidean inert atmosphere glovebox. L1 (20 mg, 0.072 mmol) dissolved in 4 mL of dichloromethane was added dropwise and the cloudy, dark orange mixture was stirred at room temperature for approximately 30 minutes. The final clear, yellow / orange solution was concentrated in vacuo to approximately ½ volume then filtered through Celite®. Product precipitation was induced by the addition of pentane (approximately 10 mL), and the resulting orange powder was collected on a frit and rinsed 3× with cold Et2O. The solid was then dissolved in dichloromethane and the solution wasAttorney Docket No. 0073605-001022 layered with pentane. Slow mixing of the solvents at –25°C yielded 30.7 mg of 3 as yellow-orange needles (96%).

[0397] Characterization of 3

[0398] 1H NMR (500 MHz, CD2Cl2) δ 9.29 (dd, J = 8.5, 1.0 Hz, 1H), 8.14 (dd, J = 8.0, 1.5 Hz,1H), 7.96 (ddd, J = 8.5, 7.0, 1.5 Hz, 1H), 7.86 – 7.79 (ddd, J = 8.5, 7.0, 1.0 Hz, 1H), 7.22 – 7.12 (m, 2H), 5.80 – 5.74 (m, 1H), 5.10 (ddd, J = 15.0, 6.0, 2.0 Hz, 1H), 4.65 (dd, J = 15.0, 2.0 Hz, 1H), 4.30 (ddd, J = 15.5, 13.0, 2.5 Hz, 1H), 3.05 – 2.98 (m, 1H), 2.01 (tdd, J = 13.0, 8.5, 2.0 Hz, 1H), 1.58 (s, 9H). (Assignments shown below and in FIG. 11O)

[0399] 13C{1H}NMR (126 MHz,, 154.98 (L), 139.32 (E), 137.00 (K),130.09 (H), 129.02 (I), 127.93 (G), 123.34 (J), 118.75 (F), 113.37 (O), 98.36 (D), 88.90 (P), 33.07 (M), 32.99 (B), 29.78 (A), 27.57 (N). See FIG. 11P.

[0400] HRMS (ESI-TOF) m / z: [M – H – 2Cl]+ Calcd for C18H20N3Pd: 384.0691. Found:384.0678.

[0401] FTIR (neat) cm-1: 3116 (m), 2968 (m), 1622 (m), 1601 (m), 1541 (w), 1486 (vs), 1312(m), 1102 (w), 964 (m), 839 (m), 772 (vs), 758 (vs), 558 (w).

[0402] Anal. Calcd. for 3 C18H21Cl2N3Pd×C0.5HCl: C, 44.51; H, 4.44; N, 8.42. Found: C,44.408; H, 4.203; N, 8.260.

[0403] NMR-scale preparation and characterization of [4][BF4]2

[0404] [4][BF4]2(1 eq, 0.011 mmol) in asmall amount of CD3CN. In a separate vial, 4.8 mg [Pd(MeCN)4][BF4]2(1 eq, 0.011 mmol) wasAttorney Docket No. 0073605-001022 dissolved in a small amount of CD3CN, then the L3 solution was added slowly. The resulting solution was pipette mixed and transferred to a J. Young valve NMR tube. Initially, a single product is observed via1H NMR, which slowly converts to SI5 and SI6 over time. The identification of [4][BF4]2as the initial product was aided by characterization of SI5 and SI6. In attempting to crystallize the initial product ([4][BF4]2) by slow diffusion of Et2O into a MeCN solution, we have isolated single crystals of SI5. The X-ray crystal structure of SI5 confirms coordination of a second equivalent of L3. The1H NMR spectrum of this complex is distinct to that of proposed [4][BF4]2. The third species observed by1H NMR, SI6, can be generated by addition of 3 equivalents of L3 to [Pd(MeCN)4][BF4]2. See FIGS. 11Q-R.

[0405] A solution-phase IR spectrum was collected by generating [4][BF4]2 from 6.6 mg[Pd(MeCN)4][BF4]2and 4.2 mg L3 in CD3CN. Half of this sample was transferred to a J. Young valved NMR tube and half was transferred to a CaF2solution cell. While IR analysis was performed, the sample was monitored via1H NMR to ensure only [4][BF4]2was present in solution at the time of measurement. A blank spectrum (CD3CN in the CaF2cell) was then collected and subtracted from the spectrum of [4][BF4]2. See FIG. 11S.

[0406] The purity of [4][BF4]2 was also confirmed by UV / Vis spectroscopy. One equivalent ofL3 was titrated into a solution of [Pd(MeCN)4][BF4]2in MeCN. A clean conversion to [4][BF4]2was observed. Details regarding data processing are given in FIGS. 12A-B:

[0407] FTIR characterization of L1 / L2 and [Pd]2+ complexes

[0408] Comparison of L1 / L2 and [1][BF4]2 / [2][BF4]2

[0409] The interpretation of the changes observed in the IR spectrum of [1][BF4]2 relative to L1(FIG. 3) was aided by comparisons to similar compounds.

[0410] For example, L1 was protonated and isolated as the corresponding [BF4]- salt ([H–L1][BF4], FIG. 12C). In the IR spectrum of [H–L1][BF4], the changes in the νC=N, νC=N+ νCC, and δCHbands (wavenumber position and intensity relative to L1) are consistent with those of [1][BF4]2(FIG. 12C). This result further suggests that these enhancements are related to charge accumulation in the heterocyclic system of [1][BF4]2.

[0411] The corresponding PtII alkyl complex of [1][BF4]2 was also prepared andcrystallographically characterized. The IR spectrum of this complex is nearly identical to that of [1][BF4]2(FIG. 13). These spectral differences are also mirrored in a comparison between L2 and [2][BF4]2(FIG. 14).Attorney Docket No. 0073605-001022

[0412] Protonolysis of [1]2+ and [2]2+

[0413] Solutions of [1]2+ and [2]2+ were generated by dissolving either 2.0 mg of [1][BF4]2(0.0029 mmol) or 2.3 mg of [2][BF4]2(0.0029 mmol) in 300 µL of CD3CN. A stock solution of HBF4·Et2O was prepared by diluting 5 µL of HBF4•Et2O (0.037 mmol HBF4) into 510 µL of CD3CN.

[0414] Three 40 µL aliquots of HBF4 solution (1 eq. HBF4 each) were then titrated into the [1]2+solution. A1H NMR spectrum was collected after each addition. Minimal changes to the1H NMR are observed until addition of the 3rdequivalent of HBF4.

[0415] One 40 aliquot of HBF4 solution (1 eq.) was then added to the [2]2+ solution and a 1HNMR spectrum was collected. A reference1H NMR spectrum of [H-L2]+was also collected, and [H-L2]+was generated in situ as follows: 1.2 mg of L2 (0.0029 mmol) was dissolved in 300 µL of CD3CN, then 40 µL of the HBF4solution was added. See FIGS. 15-16.

[0416] Ligand Exchange Experiments

[0417] Ligand cross-exchange between [2]2+ and L1

[0418] 2.5 mg ofthen dissolved in 150 µLof CD3CN. 2.1 mg of L1 (0.0075 mmol, 3.75 eq) was weighed in a separate vial and dissolved in 150 µL of CD3CN. The L1 solution was then added to the [2]2+solution and one drop of CH2Cl2was added as an internal standard. The resulting mixture was pipette mixed then transferred to a J. Young valved NMR tube. Reaction progress was monitored over 24 hours via1H NMR (see FIG. 17).

[0419] Ligand cross-exchange between [1]2+ and L2

[0420] 1.2 mg of [1][BF4]2 (0.0018 mmol, 1 eq) was weighed in a vial then dissolved in 150 µLof CD3CN. 2.8 mg of L2 (0.0068 mmol, 3.75 eq) was weighed in a separate vial and dissolved in 150 µL of CD3CN. The L2 solution was then added to the [1]2+solution and one drop of CH2Cl2was added as an internal standard. The resulting mixture was pipette mixed then transferred to a J. Young valved NMR tube. No reaction was observed via1H NMR over ca. 24 hours.Attorney Docket No. 0073605-001022

[0421] Ligand self-exchange between [1]2+ and L1

[0422] 1.8mg of [1][BF4]2 (0.0026 mmol, 1 eq) was weighed in a vial then dissolved in 150 µLof CD3CN. 1.7 mg of L1 (0.0061 mmol, 2.3 eq) was weighed in a separate vial then dissolved in 150 µL of CD3CN. The L1 solution was then added to the [1]2+solution, and the resulting mixture was pipette mixed then transferred to a J. Young valved NMR tube. A series of 2D-EXSY experiments were performed with varying mixing times (10, 100, 200, and 1000 ms). See FIGS. 18-20.

[0423] Exogeneous Ligand Additions

[0424] Portion-wise addition of PPh3

[0425] NMR experiment procedure. In a representative experiment, stock solutions of Pd alkylcomplexes were prepared by dissolving [1][BF4]2(11.2 mg, 0.016 mmol) or [2][BF4]2(12.7 mg, 0.016 mmol) in 800 mL of CD3CN. A stock solution of PPh3was prepared by dissolving 10.4 mg in 600 mL of CD3CN. A typical experiment was performed as follows: 100 mL aliquots of the Pd alkyl stock solution (0.00198 mmol) were transferred into four separate vials via syringe. Aliquots of PPh3stock solution were then added to each vial: 15 mL (0.5 eq, 0.00099 mmol), 30 mL (1 eq, 0.0020 mmol), 45 mL (1.5 eq, 0.0030 mmol), 60 mL (2 eq, 0.0040 mmol). The resulting solutions were thoroughly pipette mixed, then additional CD3CN was added such that the final volume of each sample was 300 mL. Solutions were transferred to a J. Young valved NMR tube and1H and31P{1H} NMR spectra were collected immediately. Samples were monitored over a period of approximately 3 days over which no changes were observed to the NMR spectra.

[0426] [Pd(PPh3)2(MeCN)2][BF4]2 was generated according to a published procedure5 for use asa reference: 2.2 mg [Pd(MeCN)4][BF4]2(1 eq, 0.0050 mmol) was dissolved in 200 mL CD3CN. Separately, 2.6 mg PPh3(2 eq, 0.0099 mmol) was dissolved in 600 mL CD3CN and added to the Pd solution. The resulting mixture was pipette mixed, transferred to a J. Young valved NMR tube and analyzed via31P NMR.

[0427] For [2][BF4]2, between 0 and 1 eq of PPh3, a new species is observed via 1H NMR, [2-PPh3]2+. Two signals are observed via31P NMR, which is attributed to a pair of diastereomers (likely a pair of planar chiral isomers that arise from coordination of Pd to the olefin). When a second equivalent of PPh3is added, free L2 is observed via1H NMR and [Pd(PPh3)2(MeCN)2][BF4]2. At this point, precipitation of a colorless solid in the NMR tube is also observed likely due to the low solubility of L2 in CD3CN. See FIGS. 21A-D, 22A-D.Attorney Docket No. 0073605-001022

[0428] IR experiment procedure. A stock solution of PPh3 was prepared by dissolving 6.6 mgPPh3in 700 mL of CD3CN. [1-PPh3]2+was generated by dissolving 4.9 mg [1][BF4]2(0.0072 mmol) in 400 mL of CD3CN and adding a 200 mL aliquot of the PPh3stock solution (1 eq PPh3, 0.0072 mmol). [2-PPh3]2+was generated by dissolving 5.9 mg [2][BF4]2(0.0072 mmol) in 400 mL of CD3CN and adding a 200 mL aliquot of the PPh3stock solution (1 eq PPh3, 0.0072 mmol). The solutions of [1-PPh3]2+and [2-PPh3]2+were then each divided into two 300 mL samples. One sample was analyzed via1H NMR to confirm purity and identity of the compound. The other sample was transferred to a CaF2solution cell for IR analysis. Measurements were taken in transmission mode with 16 background and sample scans at 4 cm-1resolution. A blank spectrum (CD3CN in the CaF2cell) was then collected and subtracted from the spectra of [1-PPh3]2+and [2-PPh3]2+.

[0429] Addition of [Et4N][Cl]

[0430] In a representative experiment, 2.5 mg [1][BF4]2 (0.037 mmol) was weighed in a vialand dissolved in a small amount of CD3CN. In a separate vial, 6.1 mg [Et4N][Cl] was dissolved in 500 mL of CD3CN. 100 mL of the [Et4N][Cl] solution (0.0073 mmol, 2 eq.) was then slowly added to the solution of [1][BF4]2. The resulting solution was pipette mixed, transferred to a J. Young valved NMR tube and analyzed via1H NMR.

[0431] 3 is observed as the major species. A similar spectrum was observed whenindependently synthesized 3 was dissolved in CD3CN (the sample of 3 is clean in CD2Cl2but speciation in CD3CN is more complex). See FIGS. 23, 24A-B.

[0432] A comparison between the ATR-FTIR spectra of free ligand L1 and (1κ2)-Cl2 is shownin FIG. 24C.

[0433] NMR-Scale Catalytic Reactions

[0434] The primary purpose of these experiments was to monitor the speciation of [1][BF4]2 and[2][BF4].Accordingly, the amount of substrate varies from ca. 25 eq to 135 eq. Under these conditions, the catalyst speciation AND the percentage conversion could be monitored.

[0435] General procedures. Stock solutions of the Pd complexes and olefinic substrates inCD3CN were prepared at various concentrations. Each substrate was tested in at least two independent experiments using catalyst solutions generated from different batches of Pd complex. In a representative experiment, these solutions were prepared as follows: [1][BF4]2(2.8 mg, 0.0041 mmol), [2][BF4]2(3.4 mg, 0.0041 mmol) and [Pd(MeCN)4][BF4]2(1.8 mg, 0.0041 mmol) were individually weighed in volumetric flasks. Separately, three drops of CH2Cl2was dissolved in 200Attorney Docket No. 0073605-001022 µL of CD3CN. A 50 µL aliquot of the CH2Cl2solution was added to each Pd-containing flask (CH2Cl2was used as an internal standard). CD3CN was then added to bring the total volume of each solution to 1 ml CD3CN. Cis-stilbene (12.2 mg, 0.068 mmol) was weighed into a vial then dissolved in 600 µL CD3CN. NMR-scale reactions were then set up by transferring a 200 µL aliquot of each Pd stock solution to three separate vials. A 100 µL aliquot of olefin stock solution was added to each vial. The samples were pipette mixed and transferred to J. Young valved NMR tubes. Experiments conducted in CD3NO2followed an analogous procedure.

[0436] Reaction time course data were collected via 1H NMR. The first time point was collectedimmediately after samples were prepared. All measurements were collected on a 500 MHz (CD3CN experiments) or 400 MHz (CD3NO2experiments) spectrometer. Within each time course, a common shim file was loaded before allowing the spectrometer to automatically set the shims, in order to increase reproducibility. For each reaction, percent conversion was determined by taking the ratio of starting material peak area at the first time point (when no product was observed) / starting material peak area at the final time point. Starting material peak areas were measured relative to the internal standard.

[0437] Isomerization of non-polar substrates

[0438] Positional isomerization of 1-hexene

[0439] Table 2 includes representative examples of 1-hexene isomerization by Pd complexes.Associated reaction mechanisms are shown in FIGS. 25A-B (see Inorg. Chem. 1984, 23, 3258−3261 and Organometallics 2022, 41, 3366−3372). Corresponding1H NMR spectra are included in FIG. 25C. Table 2. Representative examples of 1-hexene isomerization by Pd complexes.Attorney Docket No. 0073605-001022

[0440] Cis-Stilbene to Trans-Stilbene Isomerization

[0441] Given the acceleration observed for [1][BF4]2 and [2][BF4]2 relative to[Pd(MeCN)4][BF4]2, the conversion of cis-stilbene to trans-stilbene was carefully monitored on an NMR scale in CD3CN. Samples were prepared as described in the previous section. Relative trends are consistent over 12 replicates which spanned three sets of conditions (varying [Pd]:[substrate] ratio). Representative time course data is shown below in Tables 3A-D and FIGS. 26-31.

[0442] Concentration data were extracted from the resulting 1H NMR spectra by analyzing bothpeak intensities and peak areas of the starting material and product. A peak at 6.65 ppm (s, 2H) was chosen to monitor cis-stilbene consumption and a peak at 7.58 ppm (d, 4H) was chosen to monitorAttorney Docket No. 0073605-001022 trans-stilbene formation. Peak areas were measured by integrating each peak relative to the CH2Cl2standard peak.

[0443] Relative peak heights were determined as follows:

[0444] -For cis-stilbene, the intensity of the singlet at 6.65 ppm was measured and then dividedby the intensity of the CH2Cl2standard peak.

[0445] -For trans-stilbene, the intensities of the two peaks within the doublet (at 7.59 and 7.57ppm) were measured. The average of the peak intensities was calculated and then divided by the intensity of the CH2Cl2standard peak to give the reported relative peak height.

[0446] Two physical observables (e.g., both peak intensity and peak area) were used to increasethe confidence in our measurements. The results are consistent for both methods. The following considerations were noted for comparing the time course data sets below:

[0447] -Data points in the product area curves differ by a factor of 2 relative to thecorresponding starting material peak area points (starting material peak corresponds to 2H, product peak corresponds to 4H).

[0448] -Data points in the product peak intensity curves differ by a factor of 2 relative to thecorresponding product peak area points (peak intensity is halved because the signal is a doublet). Table 3A. Reaction Time Course Data Corresponding to FIG. 27. [1][BF4]2[2][BF4]2[Pd(MeCN)4][BF4]2is rea .29 185 093 891 525 414 045 775 659 524Attorney Docket No. 0073605-001022 128.13 1.079 0.231 4.244 0.45 128.32 1.077 0.037 4.848 0.247 128.05 0.863 0.331 4.05 0.47 146.37 1.137 0.14 4.394 0.332146.62 1.11 0.014 4.898 0.22 146.65 0.937 0.216 4.275 0.348 242 .2 173 167[1][BF4]2[Pd(MeCN)4][BF4]2Attorney Docket No. 0073605-001022 66.9 15.711 0.193[1][BF4]2[2][BF4]2[Pd(MeCN)4][BF4]2[4][BF4]2time (hr.) trans cis time (hr.) trans cis time (hr.) trans cis time (hr.) trans cis 2 1 4 5 7 1 9 4 5 6 4 2 4 1 6Table 3D. Reaction Time Course Data Corresponding to FIG. 31. [2][BF4]2[Pd(MeCN)4][BF4]2[4][BF4]2Attorney Docket No. 0073605-001022 time (hr.) trans cis time (hr.) trans cis time (hr.) trans cis 0 0.22 1.56 0 0.09 1.53 0 0.09 1.58 5 8 1 3 9 8 5 3 2 9 7

[0449] Comparison of relative isomerization rates in CD3CN and CD3NO2

[0450] Sen has reported that other electrophilic ions promote isomerization reactions faster inCD3NO2. Using a dicationic Pd catalyst, [Pd(MeCN)4]2+, Sen reports a product distribution after 20 minutes but does not specifically discuss rate comparisons (the reaction was presumably too fast).

[0451] For the geometric isomerization if cis-stilbene to trans-stilbene, the catalysts are faster inCD3NO2. For the positional isomerization of 1-hexene, no solvent dependence is observed. The polar substrates also isomerize faster in MeNO2compared to MeCN. Differing solvent dependences should not be a surprise, as the positional isomerization involves moving an allylic hydrogen while the cis-to-trans isomerization of stilbene does not (i.e., they likely occur by different mechanisms). This issue is also discussed in Organometallics 2022, 41, 3366. See FIGS. 32-33.

[0452] NMR-Scale Isomerization of Polar Substrates

[0453] Monitoring Catalyst SpeciationAttorney Docket No. 0073605-001022

[0454] Isomerization reactions were first performed on NMR-scale to monitor the speciation ofcatalysts [1]2+and [2]2+over the reaction time course. Conditions were chosen such that the concentration of both catalyst and substrate were appropriate for1H NMR analysis. A full summary of these results is shown in Table 4. Table 4. Polar-functionalized substrates isomerized by [1][BF4]2and [2][BF4]2.Attorney Docket No. 0073605-001022below. Signals associated with [1][BF4]2 / [2][BF4]2are shown in the inset of each stack of NMR spectra. In some cases, these signals are obscured by substrate / product peaks. See FIG. 34-37.

[0456] Some changes in catalyst speciation were observed at late time points in some reactions.The consumption of starting material and formation of product over time were plotted to verify thatAttorney Docket No. 0073605-001022 no noticable changes occur to the kinetic profiles of these reactions. Representative examples of1H NMR and time course data are shown in FIG. 38 and FIG. 39 for both catalysts ([1][BF4]2and [2][BF4]2). Additional results are shown in FIGS. 40-43.

[0457] Side-by-side comparison of [1][BF4]2, [2][BF4]2, [4][BF4]2 and [Pd(MeCN)4][BF4]2

[0458] Side-by-side comparisons of [1][BF4]2 / [2][BF4]2 and [Pd(MeCN)4][BF4]2 were made foreach substrate in Table 5. All experiments were conducted on NMR scale using a procedure analogous to the one described previously. These experiments were carried out multiple times under varying conditions (concentration of catalyst and substrate). Comparisons of preparative scale reactions are discussed in a later section.

[0459] Observations can be generally grouped into two different outcomes: (1)[Pd(MeCN)4][BF4]2is deactivated after isomerizing a portion of the starting material (< 20% conversion, entries 1 and 2 in Table 5) or (2) [Pd(MeCN)4][BF4]2is inactive for olefin isomerization (no product observed, entries 3 and 4 in Table 5).

[0460] [4][BF4]2 was also tested. Observations based on [4][BF4]2 generally mirror those for[Pd(MeCN)4][BF4]2. A full summary of these results is given in Table 5. Additional experimental details for a representative substrate, 5-hexen-2-one (entry 1) from Table 1, is given below.Table 5. Comparison of [1][BF4]2, [2][BF4]2, [4][BF4]2 and [Pd(MeCN)4][BF4]2 as isomerizationcatalysts for polar substrates.Attorney Docket No. 0073605-001022

[0461] 5-hexen-2-one to 4-hexen-2-one and 3-hexen-2-one isomerization

[0462] Concentration data were extracted from the resulting 1H NMR spectra by analyzing peakareas of the starting material and product. A peak at 5.82 ppm (m, 1H) was used to monitor starting material consumption, and a peak at 5.56 ppm (m, 2H) was used to monitor product formation.

[0463] Over the course of the reaction, minimal change is observed in the 1H NMR spectra of[1][BF4]2and [2][BF4]2until most of the substrate has been consumed (approximately 1-2 eq substrate remaining). At this point, a new set of signals is observed for [2][BF4]2, while [2][BF4]2appears as a mixture of the unaltered complex and a new species. In both cases, no deposition of a Pd mirror is observed. In the [Pd(MeCN)4][BF4]2catalyzed reaction, signals consistent with Pd- chelated species SI7 are observed. Representative1H NMR and time course data are given below; the two sets of examples shown (9 mol% and 2 mol% catalyst loading) were carried out using catalyst solutions prepared from two different batches of [1]2+and [2]2+. See Tables 6A-B and FIGS. 44-50.Attorney Docket No.0073605-001022 Table 6A. Reaction Time Course Data Corresponding to FIG.47. [1][BF4]2[2][BF4]2[Pd(MeCN)4][BF4]2time (hr) 4-hexenone time (hr) 4-hexenone time (hr) 4-hexenoneabe S5 . eac on me Course aa Correspondng o G. 8. [1][BF4]2[2][BF4]2[Pd(MeCN)4][BF4]2neAttorney Docket No. 0073605-001022

[0464] Eugenol to isoeugenol isomerization

[0465] Concentration data were extracted from the resulting 1H NMR spectra by analyzing peakareas of the starting material and product. A peak at 6.02-5.91 ppm (ddt, 1H) was used to monitor starting material consumption, and a peak at 6.18-6.07 ppm (m, 2H) was used to monitor product formation.

[0466] Over the course of the reaction, minimal change is observed in the 1H NMR spectra of[1][BF4]2and [2][BF4]2until most of the substrate has been consumed (approximately 1-2 eq substrate remaining). At this point, a new set of signals is observed for [2][BF4]2, while [1][BF4]2appears as a mixture of the unaltered complex and a new species. In both cases, no deposition of a Pd mirror is observed. See FIGS. 51-55.

[0467] Isomerization of Polar Substrates: High Turnover Number Experiments

[0468] Catalyst lifetimes were assessed by repeating the preceding experiments on preparativescale. Four substrates were selected from Table 3 as representative examples. All four catalysts – [1][BF4]2, [2][BF4]2, [4][BF4]2and [Pd(MeCN)4][BF4]2– were tested for each of these substrates in MeNO2.

[0469] A representative series of experiments was set up as follows:

[0470] 5.74 M stock solutions were prepared for each substrate by weighing 11.5 mmol ofsubstrate in a volumetric flask and adding MeNO2to obtain a solution with total volume of 2.0 mL. Stock solutions of [1][BF4]2, [2][BF4]2and [Pd(MeCN)4][BF4]2were prepared by separately weighing 1.6 mg (0.0023 mmol), 1.9 mg (0.0023 mmol) and 2.0 mg (0.0046 mmol), respectively, in 1.0 mL volumetric flasks and dissolving in 1.0 mL MeNO2.10 µL aliquots were removed from each Pd solution, transferred to a 1.0 mL volumetric flask diluted with MeNO2(final concentration = 2.3 × 10-5M for [1][BF4]2 / [2][BF4]2, 4.6 × 10-5M for [Pd(MeCN)4][BF4]2).

[0471] For experiments with [4][BF4]2, the catalyst solution was freshly prepared from L3 and[Pd(MeCN)4][BF4]2as follows: A stock solution of L3 was also prepared by the same procedure outlined above (final concentration = 4.6 × 10-5M). [4][BF4]2was then generated by slowly adding 300 µL of the L3 solution to 300 µL of the [Pd(MeCN)4][BF4]2(see above) solution. The resulting mixture was pipette mixed.

[0472] 50 μL of the stock solutions for [1][BF4]2, [2][BF4]2, or [4][BF4]2 were added to threeseparate vials. 25 μL of the stock solution for [Pd(MeCN)4][BF4]2was added to a fourth vial and diluted with 25 μL of MeNO2(to standardize concentrations). A 200 µL aliquot of substrate solutionAttorney Docket No. 0073605-001022 was then added to each vial. All four mixtures were pipette mixed, then the vials were sealed with caps.

[0473] Reaction progress was assessed via 1H NMR approximately every 12 hours. NMRsamples were prepared by removing 10 µL aliquots from the reaction mixtures and diluting them into 400 µL of CD3CN which had been spiked with mesitylene (to act as an internal standard; [mesitylene] = 31.0 mM). Percent conversion and TON were determined by measuring the starting material peak area relative to the internal standard (in an analogous procedure to what is described in preceding sections).

[0474] Additional details for high turnover number experiments are provided in FIG. 56 andTable 7. Table 7. Results for polar substrate isomerization under turnover limiting conditions.

[0475] Kinetic Models and Discussion of Curtin-Hammett Derived Rate AccelerationAttorney Docket No. 0073605-001022

[0476] A brief explanation is provided below regarding how suppressing concentration of theelectrophilic κ2isomer could accelerate the rate of an electrophilic isomerization. The derivation that is particularly instructive is reproduced (with some adjustments) from Tetrahedron, 1980, 1173. Consider any elementary reaction that could occur from either κ1-Pd or κ2-Pd (what is drawn is a second order reaction involving substrate). In the absence of two states, the rate of the reaction would be (rate = k2[Pdstatic][Substrate], i.e., in the left side of the diagram below). In the presence of two states, the rate of the reaction would be: (rate = k1[κ1–Pddyn][Substrate] + k2[κ2– Pddyn][Substrate]). See FIG. 57A.

[0477] Assuming that k2 is constant between the theoretical cases, above, the change in ratewhen going from structurally static to structurally dynamic would be the difference of the two rates (regardless of deceleration or acceleration): k2[Pdstatic][Substrate] - k1[κ1–Pddyn][Substrate] - k2[κ2– Pddyn][Substrate]. The expression can be simplified as: k2[Substrate]*([Pdstatic] - [κ2–Pddyn]) - k1[κ1– Pddyn][Substrate]. The effect of limiting access to the kinetically competent species) is the former term. However, the latter term (k1[κ1–Pddyn][Substrate]) will offset any of these concentration- derived effects. Thus, the magnitude of this deceleration does not exclusively depend on the thermodynamic ratio unless the latter term is negligible relative to the former.

[0478] An alternative situation where the primary effect is to limit the “active speciesconcentration” will be if k21and k12are negligible relative to the forward reactions k1and k2. This situation is “Boundary Condition I” in Chemical Reviews, 1983, 83, 83. However, this circumstance seems to be irrelevant to our current discussions because we have strong evidence that the two states interconvert quickly.

[0479] Under certain circumstances, the concentration effects could manifest in a ratedeceleration for an elementary step. However, our manuscript describes an overall rate acceleration for catalysis. Thus, we build off the analyses above to describe when an overall rate acceleration or deceleration should be expected for a multistep process. See FIG. 57B.

[0480] Now consider the effects of shapeshifting on the rate determining step AND the effectson steps that precede that step (not rate-determining). In the simplest case of A → B → C → A with B → C being rate determining, for a structurally static case (left), the rate of the reaction would berate = ^^^^[B2]. For the dynamic case on the right, it is expected that rate = ^^^^[B2] +^^^^�B1� (again an approximation is made that ^^^^does not vary from the left case to the right case, which eases comparison but is not necessary).Attorney Docket No. 0073605-001022

[0481] In this case, three independent expressions for the rate changes (to steps 1, 2, and 3,respectively) can be derived as previously. Δ() = ^^^^ ∗ [subs]([A2] − [A2]) − ^^^^[A1]Δ() = ^^^^ ∗ ([B2] − [B2]) − ^^^^[B1]= ∗ − − [C1]

[0482] than other steps, thenchanges to the depends exclusively on Δ(). In a more complex scenario, where several steps are competitive, predicting the overall will be more complex.simulation was used to demonstrate the expected effects on the rate of catalysis.Three kinetic models have been generated using COPASI to illustrate the Curtin-Hammett derived acceleration (following the same A → B → C → A mechanism).

[0484] Kinetic Model 1: Rate determining step is competitive with other elementary steps.

[0485] In Kinetic Model 1, the rate of step 2 (B → C, r.d.s.) is competitive with other steps inthe catalytic cycle. This scenario illustrates the small rate changes that would be expected when there is not an especially slow rate determining step. The reactions in the present disclosure involving the nonpolar substrates are presumably comparable to Kinetic Model 1. See FIG. 57C.

[0486] Panel (b) and Panel (c) of FIG. 57C show how the rate of the catalytic reaction would beaffected by varying kBC1. Even when the installed state is totally inactive for a step in the catalytic cycle, only a modest deceleration is to be expected (because this state can rapidly equilibrate with an active state). When kBC1= kBC2the expected time-course matches the structurally static case. For faster kBC1, a rate acceleration will be observed. However, all these kinetic effects are small compared to what will happen in Kinetic Model 2.

[0487] Kinetic Model 2: Rate determining step is much slower than other elementary steps.

[0488] The second model demonstrates the expected rate changes if the rate determining stepwere substantially slower than other steps in the catalytic reaction. Panel b shows the expected impact from concentration suppression assuming the new state is not relevant to the catalytic cycle (i.e., an off-cycle species). This model is more representative of reactions with polar substrates, where catalytic reactions might have a rate determining dissociation of the polar substrate. See FIG. 58.Attorney Docket No. 0073605-001022

[0489] Panel (c) of FIG. 58 shows how the rate of the catalytic reaction would be affected byvarying kBC1. Invoking a value for kBC1is acknowledging that this installed state can perform the rate determining step. Note that, again, when kBC1= kBC2, the expected time-course matches the structurally static case. If kBC1= 2kBC2then the time-course of the reaction is halved, and if kBC1= 5kBC2then the time course is divided by 5. These models accurately reproduce the analysis we described above (where the expected rate of the reaction is adjusted exclusively by Δ()).

[0490] Thus, when comparing structurally static systems to dynamic systems, if the dynamicsresult in a species that carries out the rate determining step more quickly (here monocationic κ1- alkyl) than the original compound (here, compared to a dicationic Pd), a rate acceleration is to be expected. The circumstances where a rate acceleration would not be observed are if the new dynamic state is slower at performing the rate determining reaction OR if the concentration effects are sufficiently severe that a different elementary step becomes rate determining. However, these concentration effects are operating on reactions that are intrinsically fast (which is to say the rate has a great distance to fall), whereas these accelerating effects are operating on steps that are intrinsically slow (which is to say that the rate has a great distance for acceleration).

[0491] Kinetic Model 3: Influence of ligand interconversion on overall rate of catalysis.

[0492] The third model demonstrates the overall rate of the reaction will vary depending on therate of interconversion between the two states B1 and B2. In this scenario, the r.d.s. (B → C, Step 2) is carried out faster by species B1 than the corresponding species B2 (kBC1> kBC2). See FIG. 59.

[0493] Panel (a) of FIG. 59 shows what would be expected based off a large difference inrelative reactivity. Panel (b) of FIG. 59 shows what would be expected based off a modest difference in relative reactivity. Both result in a rate acceleration, suggesting that increasing the rate of catalyst interconversion can result in an overall rate acceleration. This kinetic model may describe expected differences when using [2]2+vs [1]2+, especially when processing polar substrates.

[0494] Computations

[0495] To further investigate the structures and thermodynamics of the shapeshiftingcomplexes, we performed density functional theory (DFT) calculations. These calculations used the PBE010functional and the def2-TZVP11basis set, and solvent effects corresponding to acetonitrile were included using the conductor-like polarizable continuum model12(CPCM). The calculations were performed with the Gaussian 16 software package.Attorney Docket No. 0073605-001022

[0496] The ground state for square-planar these species are typically singlets. We validated thisassumption by computing the triplet states and comparing the electronic energies for different spin states (Table 8A). Table 8A. Electronic energies for singlet and triplet states of Pd complexes. Species S=0 (singlet) S=1(triplet) Pd[(MeCN)4]2+-658.241318414 Eh-658.193011263 Ehκ2-[1]2+-1255.05121013 Eh-1254.99027715 Ehκ1-[1]2+-1387.73017402 Eh-1387.66919583 Eh

[0497] The geometries of the κ1 and κ2 variants for [1]2+ and [2]2+ were optimized and the freeenergy differences were computed based on these optimized geometries. A relaxed scan was performed for the C and N atoms involved in the reversible C-N bond formation responsible for the interconversion of the two product states. The highest energy point along this scan was used as a guess structure to optimize a TS for the interconversion of product states. TS for both [1]2+and [2]2+converged with a single imaginary frequency. The computed free energies for ligand exchange from Scheme 2 are summarized in FIG. 60.

[0498] Calculated IR spectra

[0499] Ligand-based vibrational frequencies are calculated using Density Functional Theory(DFT) and summarized in Tables 8B and 8C. Table 8B. Ligand-based vibrational frequencies predicted by DFT calculations. Species νC=N,cm-1νC=N+ νC–C,cm-1δCH,cm-1Table 8C. Computed and experimental nitrile stretching frequencies for [Pd]2+complexes. Complex Computed νC≡N(cm-1) Experimental νC≡N(cm-1)Attorney Docket No. 0073605-001022 [Pd(bc)(MeCN)2]2+2438, 2435 2340 [Pd(bpy)(MeCN)2]2+2437, 2434 2334,positions and intensities are sufficiently close that they cannot be distinguished experimentally (hence why a single value is reported in the experimental table).

[0501] The computed physical quantities depend on the choice of DFT functionals. In addition,DFT is known to be less accurate for transition metal complexes. Thus, one cannot expect a perfect agreement with the experimental values. Table S8 provides a comparison of νC≡Nvalues for[Pd(MeCN)4]2+ which were computed using different functionals. The absolute results vary withdifferent functionals, demonstrating the influence the choice of functional has on the results. Inclusion of Grimme’s D3 empirical dispersion corrections14has a small effect on computed frequencies. Similarly, explicit inclusion of solvating BF4- also changes the absolute positions very little. In Table S9 we show that the functionals PBE0 and PBE provide the same qualitative trend for computed νC≡Nof all tested [Pd]2+complexes. The DFT calculations reproduce the qualitative Lewis acidity trend in νC≡Nvalues that was hypothesized regardless of the choice of functional. See Tables 9-10 below. Table 9. Comparison of different functionals for computed nitrile stretching frequencies of [Pd(MeCN)4]2+. Functional Computed νC≡N(cm-1)Attorney Docket No. 0073605-001022 Table 10. Comparison of PBE0 and PBE functionals for computed nitrile stretching frequencies of [Pd(MeCN)4]2+, shapeshifting complexes [1]2+ / [2]2+and model complex [4]2+. Complex PBE0 functional PBE functional [Pd(MeCN)4]2+2451 2450 2339 2338p p gy

[0503] To investigate the free energy barrier of the stilbene isomerization, a search wasperformed for a TS representing some point between structures B and C as described in FIG. 9. Guess structures for a TS search were gathered by performing relaxed scans of the alkene dihedral in the stilbene of κ2 / 1-[1 / 2]2+B structures at the PBE0 / def2-SVP level of theory. The structure with the highest energy was then used as a guess structure for a TS search at the PBE0 / def2-TZVP level of theory. Κ2-[1 / 2]2+structures converged with a single imaginary frequency. The C-C bond length increases from 1.388 Å to 1.478 Å and the geometry of the Pd-C becomes tetrahedral which may point towards higher single bond character. This is consistent with the proposed carbocation bond rotation. However, κ1-[1 / 2]2+TS guesses failed to converge with a single imaginary frequency. See Table 11 and FIGS. 61A-B. Table 11. Free energies for Pd-catalyzed isomerization of cis-stilbene. Species ΔG (A→B), ΔG (B→TS), ΔG (B→E), ΔG (E→A+P),Attorney Docket No. 0073605-001022* TS calculations did not converge

[0504] Optimized geometries for various chemical species pertaining to the present disclosureare shown in FIGS. 62A-S. Corresponding coordinates are summarized below in Tables 12A-N.

[0505] Optimized Geometries for κ1-alkyl complexesTable 12A. Coordinates of Optimized Geometries for κ1-[1]2+and κ1-[2]2+. κ1-[1]2+(-1387.73017402 Eh) κ1-[2]2+ (-1775.69532278 Eh)Atom x z Atom x zAttorney Docket No. 0073605-001022 H -0.354 9.339 1.799 H -0.828 9.372 1.185 H -0.687 7.997 0.693 H -0.954 7.772 0.436 9 4 9 7Attorney Docket No. 0073605-001022 H 3.551 3.192 -4.417 H 8.289 8.398 -5.264 N 5.737 1.974 -5.748 C 4.660 1.141 -6.257Attorney Docket No. 0073605-001022 H 5.391 5.392 -4.041Table 12B. Coordinates of Optimized Geometries for κ2-[1]2+and κ2-[2]2+. κ2-[1]2+(-1255.05121013 Eh) κ2-[2]2+(-1643.02903524 Eh) Atom x y z Atom x y z 1 6 8 1 0 2 0 9 6 5 6 5 7 4 2 3 1Attorney Docket No. 0073605-001022 C 1.461 8.503 1.598 C 1.259 8.379 1.517 H 0.408 9.465 -0.755 H 0.255 9.328 -0.862 8 7 7 3 1 5 8 7 0 3 9 0 8 2 6 2 9 5 3 1 4 4 5 7 0Attorney Docket No. 0073605-001022 H 0.985 5.095 -6.882 C 1.120 -0.283 -7.797 C 1.278 2.116 -6.315 5 4 9 9 7 0 1 0 9 4 4 6 6 2 8 8 2 8 2 6 0Table 12C. Coordinates of Optimized Geometry for [4]2+. [4]2+(-1388.93769439 Eh)Attorney Docket No. 0073605-001022 C 0.428 2.945 -3.700 H 1.483 8.798 -3.420Attorney Docket No. 0073605-001022 H 3.644 7.555 -3.423 H 3.212 6.793 -4.956Attorney Docket No. 0073605-001022

[0507] Optimized geometries for intermediates in cis-stilbene isomerizationTable 12D. Coordinates of Optimized Geometry for κ2-[1]2+B. κ2-[1]2+B (-1662.61875364 Eh) Atom x y zAttorney Docket No. 0073605-001022 H 4.018 10.504 0.295 C 3.289 10.956 -0.381Attorney Docket No. 0073605-001022 C 3.042 6.651 -10.350 H 1.152 5.867 -11.003Table 12E. Coordinates of Optimized Geometry for κ1-[1]2+B. κ1-[1]2+B (-1795.30728756 Eh)Attorney Docket No. 0073605-001022 H 1.755 6.629 -4.068 H 4.554 1.971 1.914Attorney Docket No. 0073605-001022 C 5.989 -0.505 -4.716 H 5.434 8.771 -6.931Attorney Docket No. 0073605-001022 H 7.968 1.263 -9.629 C 6.304 3.433 -8.403Table 12F. Coordinates of Optimized Geometry for κ -[2] B. κ2-[2]2+B (-2050.59639934 Eh)Attorney Docket No. 0073605-001022 H 4.194 10.064 -0.288 C 3.134 6.825 -0.121Attorney Docket No. 0073605-001022 1.404 4.368 -5.918 0.968 5.566 -5.120Attorney Docket No. 0073605-001022 C 8.091 0.660 -7.101 C 7.885 1.721 -7.974Table 12G. Coordinates of Optimized Geometry for κ1-[2]2+B.Attorney Docket No. 0073605-001022 4.268 4.344 1.579 5.090 3.262 1.797Attorney Docket No. 0073605-001022 1.410 9.705 0.626 7.599 8.126 -5.990Attorney Docket No. 0073605-001022 9.177 3.346 -1.678 8.663 4.641 -1.783Attorney Docket No.0073605-001022 C 5.997 3.890 -8.323 H 5.202 1.215 -8.588abe . Coordnaes o Op mzed Geomery or [ ] . [4]2+B (-1796.51348205 Eh)Attorney Docket No. 0073605-001022 H 3.742 8.403 1.590 C 1.464 6.137 0.416Attorney Docket No. 0073605-001022 H -2.947 3.026 -5.583 H -3.212 4.548 -4.692Attorney Docket No. 0073605-001022 4.747 5.427 -5.399 6.158 5.623 -5.217y . κ2-[1]2+B ® E TS (-1662.59114729 Eh)Attorney Docket No. 0073605-001022 H 1.984 12.180 0.291 H 1.136 9.567 1.745Attorney Docket No. 0073605-001022 C 6.352 0.921 -7.712 C 2.904 5.246 -8.719Table 12J. Coordinates of Optimized Geometry for κ2-[2]2+B → E TS.Attorney Docket No. 0073605-001022 κ2-[2]2+B ® E TS (-2050.56742089 Eh) Atom x y zAttorney Docket No. 0073605-001022 H 4.432 2.883 -2.986 C 2.350 6.224 -3.095Attorney Docket No. 0073605-001022 C 2.210 -1.602 -8.468 H 3.744 -3.015 -9.042Attorney Docket No. 0073605-001022 C 5.788 1.891 -10.584 H 7.068 0.280 -11.198p pTable 12K. Coordinates of Optimized Geometry for [Pd(PPh3)2(MeCN)2]2+. [Pd(PPh3)2(MeCN)2]2+(-2464.19254984 Eh)Attorney Docket No. 0073605-001022 2.712 2.366 -0.391 3.268 3.401 0.342Attorney Docket No. 0073605-001022 H -2.246 -3.957 2.322 H -1.373 -1.840 1.434Attorney Docket No. 0073605-001022 H 4.273 2.720 2.563 H 3.108 0.689 1.821[Pd(bpy)(MeCN)2]2+(-887.953572370 Eh) Atom x zAttorney Docket No.0073605-001022 N 3.349 2.006 0.038 N 3.271 -0.740 -0.027a e . oor naes o p mze eomery or [ ( py)( e )2] . [Pd(bc)MeCN2]2+(-1425.84620712 Eh)Attorney Docket No. 0073605-001022 H -0.894 -3.644 -0.099 H 1.105 -2.214 -0.092Attorney Docket No.0073605-001022 C -3.467 -2.886 0.034 C -4.516 -2.607 -0.845a e . oor naes o p mze eomery or [ (py)( e)( e )] . [Pd(bpy)(Me)(MeCN)]1+(-795.322429645 Eh) 82 68 13 25 12 40 26 04 45 49 07 01 20 45 53Attorney Docket No. 0073605-001022 N 0.471 -0.495 -0.035 H -2.879 -0.286 0.016 16 61 75 75 27 52 82 79 00 90 98 95 99 08

[0509] Crystallographic Data

[0510] Visualized crystal structures for various chemical species pertaining to the presentdisclosure are shown in FIGS. 63A-E. Associated parameters are summarized in Tables. 13A-E.

[0511] [1][BF4]2

[0512] Single crystals were obtained by slow vapor diffusion of Et2O into a MECN solution of[1][BF4]2at room temperature. Table 13A. Parameters Associated with the Crystal Structure of [1][BF4]2. Identification code kds1_autoAttorney Docket No. 0073605-001022 Space group P21 / n a / Å 12.4452(2)

[0513] 3

[0514] A solution of the 3 was synthesized in CHCl3. The sample was concentrated and thenredissolved in CH2Cl2. Single crystals were obtained by slow vapor diffusion of pentane into this CH2Cl2solution at room temperature. Table 13B. Parameters Associated with the Crystal Structure of 3.Attorney Docket No. 0073605-001022 Identification code kds17_auto Empirical formula 2(C18H21Cl2N3Pd)×2(CHCl3)

[0515] [2][BF4]2Attorney Docket No. 0073605-001022

[0516] Single crystals were obtained by slow mixing of pentane with a Et2O:MECN solution of[2][BF4]2at -25 °C. Table 13C. Parameters Associated with the Crystal Structure of 3. Identification code kds32_auto Empirical formula C34H43N6Pd×2(BF4)×C2H3NAttorney Docket No.0073605-001022 Final R indexes [all data] R1= 0.0809, wR2= 0.1619 Largest diff. peak / hole / e 1.10 / -1.10

[0518] Single crystals were obtained by slow vapor diffusion of Et2O into a MECN solution of[4][BF4]2. Table 13D. Parameters Associated with the Crystal Structure of [4][BF4]2. Identification code kds9b_auto Em iri l f rm l C H NPd ×BFAttorney Docket No. 0073605-001022 Independent reflections 4187 [Rint= 0.0622, Rsigma= 0.0635] Data / restraints / parameters 4187 / 0 / 273

[0520] Single crystals of L2 were obtained by reverse vapor diffusion of a CH2Cl2 solution ofL2 into toluene. Table 13E. Parameters Associated with the Crystal Structure of L2. Identification code kds34_autoAttorney Docket No. 0073605-001022 Radiation Cu Kα, (λ = 1.54184 Å) 2Θ range for data collection 2.420-77.770pp g p

[0522] 1. F. Wendt, O.; K. Kaiser, N.-F.; I. Elding, L., Acetonitrile and propionitrile exchangeat palladium(II) and platinum(II) †. Journal of the Chemical Society, Dalton Transactions 1997, (24), 4733-4738.

[0523] 2. Wilhelm, D.; Baeckvall, J. E.; Nordberg, R. E.; Norin, T., Stereochemistry andmechanism of palladium(II)-induced ring opening of the cyclopropane in a vinylcyclopropane. Chloro- and oxypalladation of (+)-2-carene. Organometallics 1985, 4 (7), 1296-1302.

[0524] 3. Nesper, R.; Pregosin, P. S.; Püntener, K.; Wörle, M., Homogeneous Catalysis withDicationic PdII Complexes: Aldol reaction of methyl isocyanoacetate with benzaldehyde. Helv. Chim. Acta 1993, 76 (6), 2239-2249.

[0525] 4. Ingram, A. J.; Walker, K. L.; Zare, R. N.; Waymouth, R. M., Catalytic Role ofMultinuclear Palladium–Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation. Journal of the American Chemical Society 2015, 137 (42), 13632- 13646.

[0526] 5. Sen, A.; Lai, T. W., Mechanism of palladium(II)-catalyzed carbon-carbon doublebond isomerization in olefins. Inorg. Chem. 1984, 23 (20), 3257-3258.

[0527] 6. Soro, B.; Stoccoro, S.; Agostina Cinellu, M.; Minghetti, G.; Zucca, A.; Bastero, A.;Claver, C., Effect of 5-Me substituent(s) on the catalytic activity of palladium(II) 2,2′-bipyridine complexes in CO / 4-tert-butylstyrene copolymerization. Journal of Organometallic Chemistry 2004, 689 (9), 1521-1529.Attorney Docket No. 0073605-001022

[0528] 7. Berg, N.; Bergwinkl, S.; Nuernberger, P.; Horinek, D.; Gschwind, R. M., ExtendedHydrogen Bond Networks for Effective Proton-Coupled Electron Transfer (PCET) Reactions: The Unexpected Role of Thiophenol and Its Acidic Channel in Photocatalytic Hydroamidations. Journal of the American Chemical Society 2021, 143 (2), 724-735.

[0529] 8. Gagne, M. R.; Stern, C. L.; Marks, T. J., Organolanthanide-catalyzedhydroamination. A kinetic, mechanistic, and diastereoselectivity study of the cyclization of N- unprotected amino olefins. Journal of the American Chemical Society 1992, 114 (1), 275-294.

[0530] 9. Paulson, E. R.; Delgado, E., III; Cooksy, A. L.; Grotjahn, D. B., Catalyst versusSubstrate Control of Forming (E)-2-Alkenes from 1-Alkenes Using Bifunctional Ruthenium Catalysts. Organic Process Research & Development 2018, 22 (12), 1672-1682. Example 2: Structural Dynamics Enhance Ligand Binding Affinity

[0531] Rethinking Ligand Binding Affinity

[0532] Referring now to FIG. 64, FIG. 64 includes a schematic illustrating a continuum ofligand binding affinities of various dicationic Pd compounds and a comparison between a traditional approach of ligand binding and the approach adopted by the present disclosure. The binding affinity of weak-field ligands can be enhanced by coupling ligation with an additional downhill reaction. Tuning the magnitude of this step provides an opportunity to manipulate ligand binding affinity without meaningfully perturbing the metal electronics.

[0533] Referring now to FIG. 65, FIG. 65 depicts an exemplary plot showing a correlationbetween the wavenumber of C≡N bond and the difference in chemical shift between observed31P peaks and the reference31P peak of PPh3O. The structure of a model compound for κ2–[1]2+(see FIG. 64) is illustrated. This compound is the same compound as compound [4]2+described in Example 1 above. Estimates of Lewis acidity (based on FTIR1& Gutmann-Beckett2) suggest that this compound is weakly ligated.

[0534] In addition, ligand cyclization relocates charge from Pd2+ to L1 (see Example 1).Delocalization over the aromatic system presumably stabilizes the ligand-based charge (see FIG. 3).

[0535] Evidence for a Two-State Ligand

[0536] Ligand self-exchange, as described in Example 1, demonstrates that metalation of L1 isreversible. In a 2D-EXSY experiment, cross peaks are observed between two sets of resonances forAttorney Docket No. 0073605-001022 L1 and [1]2+(Ha / Ha’ and Hb / Hb’, see FIG. 4). These observations suggest L1 equilibrates between the ligated and unbound state.

[0537] Referring now to FIG. 66, FIG. 66 includes variable-temperature UV / Vis spectra of[1]2+. These data indicate that a temperature-dependent equilibrium is operable. Comparison with thesteady-state absorption spectra of [2]2+suggests that the ligand cyclization equilibrium shifts toward κ2–[1]2+at low temperature.

[0538] Estimating Increases in Relative Binding Affinities

[0539] Increasing the driving force for cyclization enhances ligand binding affinity. Referringnow to FIG. 67A, FIG. 67A depicts a schematic illustrating the preparation of a Pd complex from L1. L1 can be further modified with the intent of perturbing the cyclization equilibrium. The derivative ligands can be compared based on the observed binding mode when ligated to neutralize a PdII, which should decrease the propensity for ligand cyclization.

[0540] Referring now to FIG. 67B, FIG. 67B depicts a schematic illustrating the preparation ofa Pd complex from L3. Two hydrogen atoms in L1 are replaced by two methyl groups, as seen in L3, and the resulting L3 enhances the stability of the cyclized ligand.3Metalation with neutral precursor Pd(MeCN)2Cl2generates a κ1-bound zwitterionic complex.

[0541] Referring now to FIG. 68, FIG. 68 depicts exemplary 1H NMR spectra (400 MHz,CD3CN) describing an exchange reaction between [1]2+and L3.2+and L3 undergo ligand exchange to cleanly generate [3]2+and L1 – further suggesting that the binding affinity of L3 is greater than that of L1.

[0542] Referring now to FIG. 69, FIG. 69 depicts an exemplary schematic showing the bindingaffinity and thermal stability of various Pd complexes described in this disclosure. Keqfor ligand cross exchange experiments were determined via1H NMR and used to order the relative binding affinities of derivative ligands. Increasing binding affinity and thermal stability were observed for several modified Pd complexes (e.g., the L3-based compound and the compound containing a 6- membered ring instead of a 5-membered ring under κ1mode) with respect to reference Pd complexes based on L1 and L2; the most stable derivatives can be refluxed in MeCN for over one week without decomposing.

[0543] Correlating Cyclization Driving Force with Protic Stability

[0544] Referring now to FIG. 70, FIG. 70 includes an exemplary schematic pertaining to theprotonolysis of Pd complexes, showing a correlation between cyclization driving force and proticAttorney Docket No. 0073605-001022 stability. Attempted protonolysis of κ1-complex yields a N-protonated free ligand. Ligand protonation likely occurs from the κ2-complex and the overall Keqfor this reaction is therefore reflective of the magnitude of ligand cyclization equilibrium.

[0545] Referring now to FIG. 71, FIG. 71 includes the change in Gibbs free energy forcyclization processes, ΔGcyclization, and pKas of various Pd complexes. Pd alkyl derivatives exhibitvarying levels of resistance to protonolysis. The most stable derivatives do not react with excessHBF4or TfOH. Ligand cyclization therefore significantly increases protection from protonation.

[0546] Benefits of Enhanced Binding Affinity

[0547] Referring now to FIG. 72, FIG. 72 includes exemplary data showing catalyticperformance of the Pd complexes described herein. Enhancing ligand binding affinity may increasecatalyst lifetime for olefin isomerization of protic substrates. Maximum turnover number wasdetermined for each catalyst by increasing substrate concentration until < 95% conversion was obtained. Observed maximum turnover numbers (TONs) are higher for ligands with higher binding affinities. Example 2 References

[0548] 1. (a) Reedijk, J.; Zuur, A. P.; Groeneveld, W. L., Complexes with ligands containingnitrile groups. Part III. Infrared spectra of coordinated methyl cyanide. Recl. Trav. Chim. Pays-Bas 1967, 86 (10), 1127-1137. (b) Purcell, K. F., .sigma.- and .pi.-Bonding effects in the coordination of the cyano group. J. Am. Chem. Soc. 1967, 89 (24), 6139-6143. (c) Wayland, B. B.; Schramm, R. F., Cationic and neutral chloride complexes of palladium(II) with the nonaqueous solvent donors acetonitrile, dimethyl sulfoxide, and a series of amides. Mixed sulfur and oxygen coordination sites in a dimethyl sulfoxide complex. Inorg. Chem. 1969, 8 (4), 971-976. (d) Purcell, K. F.; Drago, R. S., Studies of the Bonding in Acetonitrile Adducts1. J. Am. Chem. Soc. 1966, 88 (5), 919-924.

[0549] 2. P. Erdmann, L. Greb, Angew. Chem. Int. Ed. 2022, 61, e202114550.

[0550] 3. Shaw, B.L. Formation of large rings, internal metalation reactions, and internalentropy effects. Journal of the American Chemical Society 1975, 97 (13), 3856-3857. DOI: 10.1021 / ja—846a072. Example 3: New Polymers Accessed by Catalysts that Tolerate Polar Functional Groups

[0551] Nonpolar plastics such as polyethylene, polypropylene, and polystyrene are ubiquitousin daily life. Still, these materials have some unaddressed weaknesses. Because they areAttorney Docket No. 0073605-001022 hydrophobic, they do not absorb water, do not adhere to polar materials, and cannot be used to make many composite materials (especially if the other components are polar).1

[0552] Copolymerizing with other polar vinyl monomers can result in derivative polymers withnew properties – introducing (for example) oxygen permeability, dyeability, cross-linking potential, and photodegradability.1Some polyethylene / polar monomer copolymers are currently synthesized from radical processes at extreme conditions (high pressures and temperatures).1However, these extreme conditions make it difficult to control the polymerization reaction and therefore the properties of the resulting polymer (e.g., dispersities and microstructures). Overall, because copolymers featuring polar monomers remain relatively inaccessible, there are few ways to adjust certain properties of nonpolar plastics.

[0553] Transition metal catalysts that operate via coordination-insertion are a potential solutionto polar monomer copolymerization (e.g., Ziegler-Natta polymerization).2-3Despite tremendous promise, these coordination-insertion catalysts are subject to what has been termed the “polar monomer problem.” The metal catalyst olefinic monomer.4However, polar monomers are Lewis bases and tend to inhibit the polymerization reaction. For example, after polar monomer insertion, many catalysts are observed as stable chelates (“post-polar insertion” in FIG. 73). An incoming monomer needs to displace the polar functional group, an endothermic step that severely impacts catalytic activity.5This problem manifests in lower molecular weight polymers and systems that are not sufficiently active for further development. Both the academic6and industrial7community have sought catalyst designs that are not inhibited by polar monomers. Of existing catalyst design efforts, a recent perspective summarizes: “we exhaust[ed] tried and tested ligand platforms... [and] typical electronic and steric modifications... [and] we must consider more innovative strategies [for ligand design].6”

[0554] Shapeshifting Ligands for Polymerization Catalysis

[0555] The shapeshifting catalysts described in this disclosure can, at least as a proof-of-principle, address the polar monomer problem, as these catalysts are not inhibited by polar functional groups. Specifically, the ligands described in the present disclosure can be incorporated in electrophilic (Lewis acidic) transition metal catalysts – the catalysts that are generally useful for coordination-insertion polymerization.8These ligands feature two minimally Lewis basic coordinating groups: a pyrimidine and an olefin. The ligands can therefore bind as bidentate ligands, e.g., in [(κ2–L1)PdCl2]. However, when the ligands bind to a more electrophilic Pd(II) dication, aAttorney Docket No. 0073605-001022 rearrangement occurs where the pyrimidine attacks the olefinic unit. Thus, the ligands can adopt a second coordination mode, sometimes appearing as a monodentate κ1-alkyls such as [(L1)Pd(MeCN)3]2+. All charged species referred to throughout this example can be isolated as tetrafluoroborate salts, e.g., [(L1)Pd(MeCN)3][BF4]2.

[0556] Infrared spectroscopy can be used to understand how the ligand binding mode alters theelectronic structure of the transition metal complex. Relative to free ligand L1, the ligand of [(L1)Pd(MeCN)3]2+(as shown previously in FIG. 3) has greatly intensified νC=N, νC=N+ νC=C, and δCHbands. These enhancements are not observed for the ligand of [(κ2–L1)PdCl2] (FIG. 3). These observations, among other evidence presented earlier in this disclosure, strongly suggest that the C– N addition reaction is coupled to charge transfer from Pd to the ligand. Accordingly, [(L1)Pd(MeCN)3]2+is best described as a monocationic Pd with a monocationic ligand, and is more Lewis basic (nucleophilic) than most dicationic Pd.

[0557] Despite the κ1-alkyl being more thermodynamically stable, exchange spectroscopy(EXSY) on mixtures of free ligand L1 and corresponding Pd complex [(L1)Pd(MeCN)3]2+imply that a κ2- pyrimidine-olefin state exists in low concentrations, consistent with details described above in this disclosure. When the ligand undergoes retrocyclization, the charge is transferred back to Pd. Thus, the metal of the κ2-pyrimidine olefin state is a strong Lewis acid, comparable to other dicationic Pd.

[0558] Even though the ligand L1 “masks” the dicationic Pd Lewis acid, [(L1)Pd(MeCN)3]2+still promotes reactions that are unique to dicationic Pd, such as without limitation olefin isomerization, a carbocation rearrangement, and styrene polymerization, among others.9The mechanistic underpinnings of these processes are further described in Section 2.3. In head-to-head comparisons processing nonpolar substrates, our catalysts perform comparably to more traditional catalysts like [Pd(MeCN)4]2+.

[0559] Overall, by studying solution-phase speciation and observed catalytic performance, theseexperiments suggest that the ligand of [(κ1–L1)Pd(MeCN)3]2+is actively changing shape; the κ1- alkyl is equilibrating with the corresponding κ2-pyrimidine-olefin isomer. As κ1-alkyls, the metal is more nucleophilic (temporarily transferring a charge to the supporting ligand). When the ligands are κ2-pyrimidine-olefins, the metal is more Lewis acidic (the charge relocalized to Pd). Forward reactions can proceed from either of the two states, with the faster being more kinetically relevant as per the Curtin-Hammett principle.10Attorney Docket No. 0073605-001022

[0560] In head-to-head comparisons processing polar substrates, these shapeshifting catalystsgreatly outperform structurally static [Pd(MeCN)4]2+. For example, hex-5-ene-2-one (an olefin with a ketone group) chelates to [Pd(MeCN)4]2+and does not dissociate; the catalyst then decomposes to a Pd mirror. However, the catalyst [(κ1–L1)Pd(MeCN)3]2+fully processes that same substrate. The time course data shown earlier in the present disclosure is representative of what is observed for many substrates bearing polar functional groups. In catalyst performance experiments, the catalyst turned over 500,000 equivalents of the following substrate: OCH3HO .

[0561] In analogous experiments 2+, no conversion was detected. Suchremarkable improvement in functional group tolerance can be attributed to the more nucleophilic κ1- alkyl, from which polar group dissociation is more facile.

[0562] The polar monomer problem – Lewis base inhibition – is an intrinsic property of Lewisacidic transition metal catalysts. The catalysts described herein are not constrained to a highly Lewis acidic state (-2-pyrimidine-olefin). Ligand dynamics provide access to a more nucleophilic κ1-alkyl. These shapeshifting catalysts are not appreciably inhibited by polar substrate dissociation. These ligand design concepts can be applied towards catalysts for polyolefins, polystyrene, polyethylene, polypropylene, and derivatives thereof, among others. Further, the approach described herein can be used for generating new polymers that retain the attractive properties of the most successful commercial plastics.

[0563] Tuning Polymer Properties by Tuning Composition

[0564] Comparisons between the present approach and the historical copolymerization ofcarbon monoxide (CO) and ethylene are informative. Early catalysts were unacceptably slow and resulted in perfectly alternating copolymers.11-13The physical properties of these 50 / 50 copolymers are unlike polyethylene, limiting processibility (higher melting point and crystallinity). Thus began a thirty-year campaign to lower the CO content to single digit percentages.12, 14To simplify an enormous body of work, catalysts that are capable of multiple consecutive ethylene insertions must strike a delicate balance of being Lewis acidic enough to coordinate ethylene (the nonpolar monomer) but not too Lewis acidic that CO coordination becomes irreversible.12Popular catalyst paradigms progressed from monocationic [PdII–alkyls]+, to neutral PdII–alkyls,15-17and most recentlyAttorney Docket No. 0073605-001022 to neutral NiII–alkyls.14These Ni catalysts can attain single digit incorporations of CO. The non- alternating low CO / polyethylene copolymers are processible via conventional injection molding, have tensile strength comparable to polyethylene, but also have new properties such as photodegradability.14Meanwhile, the Pd catalysts have been commercialized and resultant polyketones sold by Shell (Carilon) and Hyosung (POKETONE).

[0565] Pursuing other nonpolar / polar copolymers is thought to require similar campaigns inpursuit of “Goldilocks” Lewis acidity. Accordingly, specialty synthetic strategies have been adopted. For example, Changle Chen has achieved the terpolymerization of ethylene, 1-hexene, and olefin bearing eugenol-like functionality (the polar component, see FIG. 75, top).18Because the eugenol units can coordinate to transition metal cations, introducing different metal ions to the terpolymer resulted in six derivative polymers, each with different mechanical properties. The Fe3+derivative was self-healing, which was attributed to dynamic bonding events between the eugenol-unit and the metal ions. However, the eugenol units had to be introduced as protected nonpolar silyl ethers and unveiled post-polymerization – adding two synthetic operations to the generation of the desired polymer (FIG. 74). This report illustrates that incorporating even a single polar monomer can lead to combinatorial opportunities for obtaining new polymer properties, though the synthetic strategy can be cumbersome.

[0566] The two-state catalysts described herein offer a third strategy for polar monomerincorporation – circumventing the need for precise tuning of the catalyst (like in CO / ethylene copolymerization) and the need for specialty synthetic strategies (like in the eugenol terpolymer). A general tolerance for polar functional groups can be obtainable so long as one catalyst state is electrophilic enough to coordinate / activate the nonpolar monomer (the κ2-pyrimidine-olefin) and the other state is nucleophilic enough to encourage polar monomer dissociation (the κ1-alkyl).

[0567] The functional group tolerance observed in olefin isomerization appears to betransferable to polystyrene polymerization. For example, [Pd(MeCN)4]2+is known as a good catalyst for converting styrene into polystyrene; when styrene is used at 9.0 M, the resulting polymer Mw was ~ 70,000 (Mw all determined by gel permeation chromatography, GPC).19In a head-to-head comparison using non-optimized experimental conditions (styrene was used at a concentration of 0.12 M), [Pd(MeCN)4]2+generated polystyrene with Mw ~ 1,000. The shapeshifting catalyst the catalyst [(L4)–Pd(MeCN)3]2+generated polystyrene with Mw ~ 3,400. Thus, the catalyst describedAttorney Docket No. 0073605-001022 herein compares favorably to existing good catalysts for polystyrene, though conditions can be optimized to obtain higher Mw polymers.

[0568] However, major differences in catalyst performance were observed using the eugenol-like styrene derivative, as shown in FIG. 75.

[0569] Under identical conditions as above (just varying monomer identity), [Pd(MeCN)4]2+decomposes to a Pd mirror before the monomer is depleted. In contrast, the shapeshifting systemdescribed herein completely converts the eugenol-like styrene derivative into the correspondingpolymer. Unlike the parent polystyrene, this new polymer is soluble in MeCN and not amenable to GPC analysis. In an additional experiment using a 99 / 1 mixture of styrene / 1, the shapeshifting catalyst generated the corresponding copolymer with Mw ~1,000.

[0570] Thus, at least under these conditions, the shapeshifting catalysts are much more tolerantof the polar and functionalized styrene-like monomer. Initial observations suggest that generating copolymers of differing ratios could be as easy as premixing appropriate ratios of the two components prior to introducing catalyst. Given the close structural relationship of the present working copolymerization system and previous work, it is likely that the previously successful combinatorial approach can be replicated in obtaining new polymer properties by incorporating different transition metal cations (FIG. 75).1, 18. However, the synthetic method described herein allows one to more easily tune the copolymer composition, which makes it possible to more finely tune the polymer properties. For example, if any of the polymers proves self-healing, factors that determine how the monomer composition affects the speed or degree of self-healing can be identified accordingly.

[0571] The systems described herein have proven generally tolerant of polar functional groupsand can be applied to copolymerization of other monomers. The ratio of the two monomers in a copolymer can be predicted by (a) the relative monomer binding affinities to the catalyst and (b) relative rates of insertion (see FIG. 73).5, 13, 20In the copolymerization system, the eugenol-type functionalization does alter the electronic properties of the styrenyl monomer. Thus, there is a possibility that the monomer is not randomly distributed throughout the polymer.21This potential problem can be remedied by distancing the polar functional group from the arene of styrene (e.g., by installation of a methylene). The additional methylene linker can be used to minimize the possibility of non-random distribution.Attorney Docket No. 0073605-001022

[0572] The present polymer design focuses on tuning polymer properties by altering monomercomposition – a strategy that is only practical because the catalysts described herein are so functional group tolerant. For example, solid propellants for rocketry use a polymer to bind oxidizing agent, fuels, and additives into an elastomeric mass. Currently, a popular matrix is generated by curing hydroxy-terminated polybutadiene (HTP)22-23with polyisocyanate reagents.24While these polymers have desirable mechanical properties, they also lower the energy density of the solid propellant. Replacement polymers such as glycidyl azide polymer (GAP) are thought to be good prospects for higher-energy density propellants.25These polymers feature energetic functional groups (sometimes referred to as explosophores), which upon decomposition release energy. However, the GAP derived polymers tend not to have the desired mechanical properties.26

[0573] Developing next generation propellants has been slowed by relatively inflexiblesynthetic methods.27For example, GAP is mostly generated from the anionic polymerization of epichlorohydrin (FIG. 76). This reaction installs the needed terminal hydroxy groups and installs chlorides off the polymeric backbone. The azide groups are then installed using NaN3.25This synthetic strategy leaves little room for modifying the structure and therefore the properties of the resultant polymer. Additionally, the strategy installs an additional methylene (initially as a chloromethyl, which then is azidated) onto every other carbon in the polymer backbone, diluting the energy density.

[0574] The energetic content can be increased by increasing energetic monomer content.Generally, explosophores like azides are so termed because the group has a positive heat of formation – releasing energy upon decomposition. However, these positive heats of formation are offset by negative heats of formation for other functional groups. Concepts like oxygen balance are strong predictors of inherent danger. In the present work, the low ratio of azide to carbon is such that neither the monomers nor the resulting polymers are likely to be energetic materials. However, the design principles from such work can be applied towards solid propellants, e.g., using polyazido- styrenes as energetic monomers or by installing azides into shorter repeat units like polyethylene.

[0575] With the general tolerance of polar functional groups, as described herein, a crosslinkinghydroxy unit28and an energetic azido unit29can be introduced as separate monomers. To retain the processability of polystyrene, styrene can be used as one of the monomers to perform a terpolymerization reaction (FIG. 77, first step). Such modular approach will allow one to tune for an elastomeric material, e.g., by adjusting the quantity or identity of the hydroxy containing monomerAttorney Docket No. 0073605-001022 (which can be crosslinked using polyisocyanate). If generating an elastomeric material proves challenging, then the hydroxy unit can be excluded, and existing strategies for making elastomeric polystyrenes can be used instead.30-31Several such elastomeric polymers can be prepared with varying energetic content by altering the percentage of incorporated azido unit. The energetic content can be quantified by performing thermogravimetric analysis and / or differential scanning calorimetry. A correlation between energetic content and percentage azide incorporation can accordingly be obtained. Therefore, the approach described herein provides modularity when tuning polymer properties.

[0576] Azide-functionalized polymers are particularly useful for several ongoing research anddevelopment efforts. For example, flame retardant polystyrenes are used industrially. These polymers predominantly obtain their flame resistance via halogenated additives. However, the halogenated compounds – either the additives themselves or the halogenated byproducts they generate – persist in the environment.32-33Accumulating halogen compounds are increasingly a public health concern, resulting in calls for environmentally conscious management.34

[0577] The 1,2,3-triazole is a good non-halogenated flame retardant. These triazoles are thoughtto imbue flame retardance by encouraging char (insulating the polymer-air interface, especially in conjunction with phosphorus additives)35-36and by releasing non-flammable vapors like N2or NH3.37-39Several “drop-in” epoxy-resins based on the triazole compare favorably to epoxy resins generated from bisphenol C (a benchmark halogenated flame retardant).37-39

[0578] Although the mechanism of flame retardancy should prove transferable, the triazoleshave not been tested in polystyrene. While 1,2,3-triazoles can be generated from copper-mediated azide-alkyne “click” chemistry,40-41installing the requisite functionality on polystyrene has historically been synthetically cumbersome.42-43In contrast, the azido functionalized polymers, as described earlier in this disclosure, can be used to imbue flame resistance (FIG. 77, second step). Flame resistance can be quantified through pyrolysis-combustion flow calorimetry.

[0579] The present work showcases the usefulness of catalysts that generally tolerate polarfunctional groups. With these catalysts, functional groups can be expediently installed into polystyrene. Rapid access to a family of related polymers (e.g., by altering the composition of input monomers) can facilitate the tuning of polymer properties. Alternatively, that family of related polymers can be diversified to furnish combinatorial opportunities for polymer development. TheseAttorney Docket No. 0073605-001022 findings are also transferable for designing polyolefin / polar monomer copolymers, thereby amplifying efforts in catalyst design.

[0580] If and When More Thermodynamic Protection is Needed

[0581] When olefins coordinate to a Lewis acidic metal ions (like the dicationic Pd catalystsabove), they lose electron density and become more electrophilic. Eisenstein / Hoffmann44and Sen45have both suggested that the coordinated olefin “slips” to the corresponding κ1-alkyl, generating carbonium character at the β-position, consistent with details described above in this disclosure. This activation mode causes aryl alkenes (styrenes) to polymerize, and terminal alkyl alkenes to isomerize. Thus, the present work can demonstrate functional group tolerance by synthesizing a terminal alkene bearing a functional group of interest several methylenes away. The catalyst speciation can be examined throughout the corresponding olefin isomerization reaction. The observations have proven transferable to styrene derivatives bearing the same functional group. For example, prior to attempting the eugenol-like polymerization shown FIG. 75, a corresponding eugenol-derived alkene was successfully isomerized and no catalyst decomposition observed, consistent with details described above in this disclosure. Azido- or hydroxyl-functionalized substrates can also be used.

[0582] Another surprising observation has been the tolerance of protic functional groups. Uponcoordination to a Lewis acidic metal, these protic functional groups are further acidified. Many protic substrate / catalyst complexes transfer protons to more basic components in solution, which would convert dicationic Pd catalysts into monocationic Pd complexes. These monocations are less Lewis acidic and promote neither styrene polymerization nor olefin isomerization.9, 46Thus, proton loss can be interpreted as a mechanism for catalyst deactivation. However, the catalyst described herein turned over more than 500,000 equivalents of protic substrate, as described above, which suggested to us that the ligands offer some unusual mode of protection.

[0583] A deactivating proton transfer was observed for the first time when studying hydroxylgroup tolerance, using 4-penten-1-ol as a model substrate (see FIG. 78). By monitoring catalyst speciation over time by1H NMR, [L1–H]+was identified as the major ligand-based product. Once the ligand is protonated and dissociates from the metal center (Pd), the Pd undergoes problematic reactions with the substrate, eventually decomposing to a Pd mirror.47The catalyst lifetime can beextended if extra equivalents of free ligand L1 are added to solution. While free substrate 3 is not themost acidic substrate used, in the presence of dicationic Pd, 4-penten-1-ol undergoes a cyclizationAttorney Docket No. 0073605-001022 reaction that greatly enhances its acidity (oxonium ions have a pKabelow 0 in MeCN48). The high driving force for proton transfer accounts for why protonated ligand [L1–H]+was observed in this singular case.

[0584] The reason why these ligands are difficult to protonate stems from the unusual approachto ligand design described herein. Supporting ligands are Lewis bases and binding affinity to the Lewis acidic metal is determined by the strength of the Lewis acid / Lewis base interaction (LA / LB). However, the ligands described herein coordinate and undergo a cyclization reaction. A thermodynamic cycle (FIG. 79) breaks the overall ligand binding affinity (ΔGbind) down into these two component parts (ΔGLA / LB+ ΔGcyc). Thus, the cyclization reaction provides thermodynamic protection against any de-ligation that does not exist for more traditional supporting ligands. Density functional theory calculations indicate that for [L1–Pd(MeCN)3]2+, the cyclization reaction is worth ~7.2 kcal mol-1(performed with the PBE0 functional, def2-TZVP basis set, and conductor-like polarizable continuum model). Phrased differently, because the κ1-alkyl undergoes the uphill retrocyclization prior to protonation, it is implied that protonating off the ligand of [L1– Pd(MeCN)3]2+will require 5.2 pKaunits more driving force than protonating free ligand L1.

[0585] The present work provides for development of ligands with further thermodynamicprotection against de-ligation, which can be achieved by increasing the cyclization driving force. The cyclization driving force can be modified by either: (a) altering the pendant alkene to encourage cyclization or (b) altering the π system to further delocalize charge. The overall ligand binding affinities can also be quantified by measuring ligand exchange equilibria. The two components for ligand binding cannot be deconvoluted with the present experimental approach, but estimates can be obtained using DFT (anchored by experimental observations). The need for greater driving force will be further contextualized in the pursuit of catalysts for polyethylene / polypropylene.

[0586] For example, most cyclization reactions are encouraged by installing geminal dimethylsubstituents into the carbocyclic backbone (the Thorpe-Ingolde effect).49L2, a homoallylic geminaldimethyl derivative of L1, was prepared accordingly (FIG. 80). Mixtures of [L1–Pd(MeCN)3]2+ / L2establish an equilibrium with [L2–Pd(MeCN)3]2+ / L1. Running the reaction in either the forward or the reverse direction results in an observed equilibrium constant KL2 / L1= 2.0, corresponding to ΔG of 0.4 kcal mol-1(the difference in overall ligand binding affinity). Similarly, for L3, the pyrazole of L1 has been replaced with an indole. This substitution delocalizes charge over a larger π-system after cyclization – increasing the driving force for cyclization. The corresponding ligand exchangeAttorney Docket No. 0073605-001022 experiments result in a KL3 / L1that is too large to be measured by1H NMR. This observation corresponds to ΔGoverallthat exceeds 3 kcal mol-1. To obtain a more accurate measurement, a ligand of intermediate binding affinity L* can be identified. By separately measuring KL* / L1and KL3 / L*, KL3 / L1can be determined as KL* / L1× KL3 / L*.5

[0587] Thus far, the derivative ligand with the greatest binding affinity to dicationic Pd is L4(FIG. 80). Relative to L1, (a) geminal dimethyl substituents are installed on the allylic position of the pentenyl unit and (b) the pyrazole is replaced with indole. From a series of ligand exchange experiments, it is determined that these two alterations result in at least 9 kcal mol-1greater binding affinity. Thus, L4 has at least 6.6 pKaunits of additional thermodynamic protection relative to L1. The catalyst [L4–Pd(MeCN)3]2+smoothly processes the previously problematic substrate in FIG. 78; and no [L4–H]+was observed. Thus, these new ligands and their associated ligand design strategy can be used to diffuse problems encountered in other contexts of the present invention.

[0588] The protection from de-ligation obtained is already substantial. The followingobservations are illustrative. All the ligands appear as κ1-alkyls when metalating with dicationic [Pd(MeCN)4]2+(e.g., [L1–Pd(MeCN)3]2+). In contrast, when ligands L1-L3 are metalated on to a PdCl2synthon (e.g., Pd(MeCN)2Cl2), they are observed as κ2–pyrimidine-olefins (e.g., [(κ2– L1)PdCl2]). The thermodynamically preferred coordination mode can be rationalized based on charge stabilization. For dicationic Pd, charge delocalization is preferred (monocationic ligand and monocationic Pd), so the ligands are observed as a κ1-alkyls. For neutral palladium dichlorides, the advantage for the charge separated state is reduced, so the ligands are observed as a κ2-pyrimidine- olefins. However, L4 is an exception in that the ligand is observed as a κ1–alkyl, even for the neutral palladium dichloride [(L4)(MeCN)PdCl2] (FIG. 81). The driving force for cyclization is so great that a zwitterion is generated.

[0589] Regarding two-state catalysis, these thermodynamic changes assuredly perturb theequilibria between the nucleophilic κ1-state and the electrophilic κ2-pyrimidine-olefin state. However, even if these changes suppress the concentration of the electrophilic state, these catalysts will still be active for electrophilic activations like styrene polymerization or olefin isomerization so long as the two states interconvert rapidly.10Rapid interconversion between the two states is suggested by (a) similar catalytic performance for all the derivative complexes and (b) historical information on the kinetics of C–N addition. Intermolecular amine additions to dicationic Pd-olefin complexes have documented barriers that span 4–8 kcal mol-1.50-51The two-states of theAttorney Docket No. 0073605-001022 shapeshifting ligands interconvert via an intramolecular variant of this C–N addition, which is presumably faster. For comparison, the barrier to rotation about the C–C bond of ethane is -3 kcal mol-1(from a staggered to eclipsed conformation).52

[0590] The work described herein provides support for the polymerization of functionalizedpolystyrenes described above in this disclosure. Increasing thermodynamic driving force for ligation will protect against de-ligation, and therefore many types of catalyst deactivation. Thus far, regardless of how much driving force we include in the cyclization reaction, the catalyst retains access to the reactive electrophilic state.

[0591] Catalysts for Polyolefins

[0592] Two-state catalysts are a framework for potentially resolving the polar monomerproblem for polyolefins. However, the dicationic Pd compounds synthesized thus far are not active in ethylene / propylene polymerization. The discussion below applies current design principles to a major subclass of catalysts for polyolefin polymerizations: monocationic Pd alkyls ([Pd–alkyl]+, FIG. 82).53-57This subclass was selected based off their resemblance to the existing systems described earlier in this disclosure, though the two-state framework could be useful for other major catalyst classes as well.

[0593] Transferring charge from Pd to the supporting ligand via C–N addition is likely morechallenging for monocationic Pd–alkyls than for dicationic Pd. An informative comparison: the addition of ammonia to a neutral [Rh–olefin] complex is reported as -30 kcal mol-1more uphill than the corresponding reaction in an analogous [Pd-olefin]+complex.50-51This comparison is not perfect – the current systems have more positive charge overall and the C–N addition is intramolecular. Thus, 30 kcal mol-1can be viewed as a conservative upper limit. The > 9 kcal mol-1driving force obtained with L4 may represent a major fraction of the needed perturbation (consider [(L4)(MeCN)PdCl2], which separates charge even for a neutral compound).

[0594] There is an absence of appropriate synthetic methods for preparing [Pd–alkyls]+. Mostoften, these compounds are prepared by (a) protonolysis of a dialkyl (e.g., Pd(CH3)2) or (b) abstracting chloride from Pd(CH3)(Cl) (e.g., with AgBF4). Both methods of generation rely on the synthesis of a neutral ligated Pd precursor. However, most of the shapeshifting ligands bind weakly to these neutral precursors as κ2-pyrimidine-olefins; they do not undergo a downhill cyclization reaction. These weak associations make it challenging to isolate the needed ligand / metal precursors.Attorney Docket No. 0073605-001022 The ligand L4 (or ligands with even higher binding affinity) may be an exception to the general observations made thus far.

[0595] Even if the ligand / metal precursors are isolated successfully, the resulting [Pd–alkyls]+are likely to be reactive and challenging to isolate. Most of the synthetic procedures are performed at cryogenic temperatures. The desired compounds are repeatedly reported to decompose at room temperature, and in some cases as low as –40 °C.13, 58These operational challenges have also made it impractical to add a methyl anion equivalent to the dicationic Pd compounds from earlier work.

[0596] An unconventional strategy can be adopted to access mechanistically relevantcompounds – targeting the synthesis of a “post polar insertion” state. Two such compounds have been reported as part of wider investigations.5, 59Both were easily handled after isolation from a reaction mixture (stable to heating at 60 °C and 100 °C). Furthermore, as catalysts, these compounds are reported to be equally active as the corresponding [Pd–alkyls]+(both are thought to be “on- cycle” species). Thus, it is likely that the “post polar insertion” states are (a) an equally valid target for polyolefin catalysis and (b) may be stronger starting points for carrying out mechanistic work. These compounds are subsequently referred to as [Pd–metallacycles]+in order to differentiate them from the [Pd–alkyls]+. Vinyl acetate can be used as a representative polar monomer (e.g., in FIG. 84).

[0597] To the best of the inventors’ knowledge, there are no general procedures for synthesizingthe needed [Pd–metallacycles]+. The two previously prepared compounds were generated by inserting a polar monomer into a reactive [Pd–alkyl]+– the synthon that has generally proven troublesome.

[0598] In initial work, a mild synthesis was developed for the desired [Pd–metallacycles]+,repurposing a synthetic method for octadienyl ligands.60This protocol was developed using the traditional and inexpensive bidentate dinitrogen ligand 2,2-bipyridine, which made it possible to compare1H NMR data to literature reported values. Mixing Pd2(dba)3, an alcoholic precursor of the first monomer unit, and the protonated salt of the bidentate ligand (FIG. 83, top) results in1H NMR where the only observable signals correspond to the desired [Pd–metallacycle]+and the dba. Similar observations were made using the shapeshifting ligand L3 (which ligates as a κ1-alkyl, FIG. 83, middle). This synthetic route avoids the ligated neutral PdIIprecursor (direct ligation to monocationic Pd). This protocol may be especially useful for weakly binding ligands – ones which bind acceptably to monocationic PdIIbut will not bind to less Lewis acidicAttorney Docket No. 0073605-001022 neutral PdII. Alternative alcoholic precursors can be synthesized to install other neutral chelating functionalities (e.g., FIG. 83, bottom).

[0599] Using these [Pd–metallacycles]+, questions about using functionalized monomerscan be addressed. For example, if vinyl acetate is used as a polar monomer, will the growing polymer insert into the α- or β- position (FIG. 84). Previous work was inconclusive because both outcomes were observed in varying ratios and further confounded by the interconversion between the two states.5The interconversion between the two states can be studied by independently synthesizing both the α- and β-insertion product from the corresponding hydroxy precursor (FIG. 83, middle and bottom). Their interconversion reactions can be studied to determine if they occur spontaneously (first order in complex) and / or in response to stimuli (e.g., by adding one equivalent of olefinic monomer, in which case a second order reaction overall may be observed). By first quantifying the equilibrium between two states, more complex outcomes can be deconvoluted, as any interconversion steps can be explicitly accounted for. Thus, relative rates of insertion into both the α- and β- isomers can be determined. [(L3)Pd–metallacycleβ]+has already been generated based on such novel synthetic method.

[0600] For catalytic polymerizations, the studies described herein are directly related to chain-branching. Stereoelectronic environments that favor β-insertion will result in linear polymers, and those favoring α-insertion will result in branched polymers. By repeating these studies with different ligands and / or substrates, guiding principles can be identified Similar work can be designed to generate descriptive models for tacticity, chain walking, chain termination, chain propagation, and chain reinitiation. The work described herein can demonstrate the considerable potential of stable systems that are amenable to mechanistic work.

[0601] Shapeshifting Catalysts for Polyolefins

[0602] A shapeshifting ligand can provide several advantages to polyolefin catalysis. Forethylene / CO copolymerization (the most mature nonpolar / polar copolymerization), the ortho- phosphinobenzenesulfonate ligands were amongst the first to achieve non-alternating ethylene / CO copolymerization (e.g., in FIG. 85).12, 15, 54Intensive research efforts have led to a consensus as to how these ligands address CO inhibition. The nonsymmetrical monoanionic bidentate ligand chelates through an anionic sulfonate and a neutral phosphine, the former of which has a stronger trans- effect. The “post ethylene insertion” has the growing polymer trans- to the anionic sulfonate ligand, however, the subsequent ethylene adduct has the growing polymer trans-to the neutralAttorney Docket No. 0073605-001022 phosphine. Based on this observation, Barry pseudorotation has been invoked as a key step (FIG. 85). This stereoisomerism would (a) place the more nucleophilic sulfonate trans-to the polarfunctional group (that needs to be displaced) and (b) assist in subsequent ethylene coordination(stronger backbonding to ethylene). This mechanism of addressing the polar monomer problem is conceptually like what we have proposed as the advantage of our shapeshifting ligand platforms.

[0603] Stereochemistry is also likely to be important for understanding the effect of theshapeshifting ligands. Much like the case in FIG. 85, for [(L3)Pd–metallacycleα]+, the growing polymer appears opposite to the ligand with the greatest trans- influence. However, the shapeshifting ligand dynamics may accelerate the key stereoisomerism step (FIG. 86). Recall that documented barriers for C–N addition / elimination span 4–8 kcal mol-1.50-51By comparison, for the ortho- phosphinobenzenesulfonate, in the absence of a stimulus, the barrier to stereoisomerism was estimated as 20 kcal mol-1.61The reaction can be accelerated by an incoming ligand to a certain degree.62However, the shapeshifting ligands do not need an external ligand stimulus to accelerate the pseudorotation, as the ligand interconversion process results in an additional coordinating ligand. Overall, because (a) polar group dissociation is accelerated by stereoisomerism and (b) stereoisomerism is accelerated by an incoming ligand, the class of ligands described herein may be even more advantaged for displacing polar functional groups. Experimentally, the rate of shapeshifting can be perturbed by further derivatizing the ligands described herein, e.g., by installing a terminal substituent on the alkene (see L5, is already synthesized and metalated).

[0604] Summary

[0605] The extraordinarily successful commercial plastics discussed herein – polystyrene andpolyolefins – have already altered the history of our planet. However, these nonpolar plastics still have many unaddressed weaknesses. New properties can be imbued into these legacy plastics once the polar monomer problem is resolved. Derivative copolymers featuring low polar monomer incorporation are amongst the best options for continuing to use our developed infrastructure for plastic processing.

[0606] The inherent oxymoron for the polar monomer problem is: the Lewis acidic catalyststhat are useful for olefin polymerization are also the ones most prone to polar monomer inhibition. Rather than trying to find the “perfect” balance of Lewis acidity / basicity, the approach described herein shows that a catalyst can be both Lewis acidic and Lewis basic through ligand dynamics – bifurcating between two states. By applying this approach to Pd complexes, polar group toleranceAttorney Docket No. 0073605-001022 can be achieved. The resulting complexes polymerize both styrene and polar styrene derivatives. These catalysts can achieve the needed control for precision synthesis of specialty polystyrenes. A framework to resolve encountered problems is also presented, which imbues the ligands described herein with greater thermodynamic protection. The synthetic method described herein provides a new entry point for addressing unresolved questions surrounding the polar monomer problem. The shapeshifting ligand framework described herein also aligns well with previous findings on state-of- the-art catalysts.

[0607] Additional data are provided in FIGS. 87-111.

[0608] Referring now to FIG. 87, FIG. 87 includes exemplary data including wavenumbers ofC≡N bonds in various Pd complexes and the shift in wavenumber with respect to a reference [PdL4]2+complex. Catalytic activity of these Pd complexes is consistent with the two-state catalytic mechanism described herein.

[0609] Referring now to FIG. 88, FIG. 88 includes various isomerization and polymerizationsthat can be catalyzed by the shapeshifting catalysts described in the present disclosure.

[0610] Referring now to FIG. 89, FIG. 89 includes exemplary time course data of theisomerization reaction from cis-stilbene to trans-stilbene catalyzed by various Pd-containing complexes described herein.

[0611] Referring now to FIG. 90, FIG. 90 includes a catalytic cycle of isomerization of 5-hexen-2-one, a polar substrate.

[0612] Referring now to FIG. 91, FIG. 91 includes FIG. 91 depicts exemplary time course dataof the conversion from 5-hexen-2-one to 4-hexen-2-one, using [Pd(MeCN)4]2+as a catalyst. S = MeCN.

[0613] Referring now to FIG. 92, FIG. 89 includes exemplary data of catalytic conversion from5-hexen-2-one to 4-hexen-2-one, using [(L1)Pd(MeCN)3]2+as a catalyst. S = MeCN.

[0614] Referring now to FIG. 93, FIG. 93 includes exemplary data of catalytic conversion from5-hexen-2-one to 4-hexen-2-one, using [(L2)Pd(MeCN)3]2+as a catalyst. R = C6H4-t-butyl. S = MeCN.

[0615] Referring now to FIG. 94, FIG. 94 includes various exemplary polar substratescompatible with the shapeshifting catalysts described herein.Attorney Docket No. 0073605-001022

[0616] Referring now to FIGS. 95-102, FIGS. 95-102 include various reaction mechanisms(e.g., protonolysis) pertaining to the Pd complexes described herein and associated thermodynamic data.

[0617] Referring now to FIGS. 103-104, FIGS. 103-104 include schematics describingpreparations of various Pd complexes described herein.

[0618] Referring now to FIG. 105, FIG. 105 includes schematics pertaining to the preparationof a polystyrene homopolymer and a hydroxylated styrene / styrene copolymer (e.g., a copolymer of 4-vinylphenol and styrene) using the shapeshifting catalysts described in the present disclosure.

[0619] Referring now to FIG. 106, FIG. 106 shows an exemplary styrene / styrene copolymerfilm and its degradation in air.

[0620] Referring now to FIG. 107, FIG. 107 shows the evolution of IR spectra for ahydroxylated styrene / styrene copolymer produced using the shapeshifting catalysts described herein.

[0621] Referring now to FIG. 108, FIG. 108 includes thermogravimetric analysis (TGA) anddifferential scanning calorimetry (DSC) data of a polystyrene homopolymer prepared using the shapeshifting catalysts described herein.

[0622] Referring now to FIG. 109, FIG. 109 includes 1H diffusion-ordered spectroscopy (1HDOSY, 500 MHz, C6D6) data of the polystyrenein FIG. 108. The diffusion coefficient, D, of the polystyrene homopolymer is first calculated based on an exponential attenuation of the1H NMR signal intensity, and the weight average molecular weight (Mw) is estimated based on D using a calibration curve (Macromolecules 2012, 45, 24, 9595–9603). The weight average molecular weight (Mw) determined by1H DOSY is ca. 3200 Da, in line with the Mwdetermined by gel permeation chromatography (GPC), which is ca. 3400 Da. It is worth noting that the molecular weight of the polymer can be adjusted or finetuned by, e.g., addition of 1,4-divinyl benzene or the like to allow multiple shorter polymer chains to be crosslinked together. A person of ordinary skill in the art, upon reviewing the entirety of this disclosure, will be able to recognize suitable means to improve or optimize the protocols described in this disclosure in order to prepare polymers with larger molecular weights or topologies not explicitly described herein.

[0623] Referring now to FIG. 110, FIG. 110 includes thermogravimetric analysis (TGA) anddifferential scanning calorimetry (DSC) data of a hydroxylated styrene / styrene copolymer prepared using the shapeshifting catalysts described herein.Attorney Docket No. 0073605-001022

[0624] Referring now to FIG. 111, FIG. 111 includes a comparison of the IR spectra of ahydroxylated styrene / styrene copolymer film freshly cast from acetone and aged for ca. one month, respectively. The hydroxylated styrene / styrene copolymer film was prepared using the shapeshifting catalysts described herein.

[0625] Referring now to FIG. 112, FIG. 112 depicts exemplary 1H NMR spectra (400 MHz,CDCl3) of a dimerized product of 4-styrenesulfonate. The dimerized product is synthesized using a shape-shifting catalyst described herein, specifically 0.5 mol% of [1][BF4], in nitromethane (MeNO2) at room temperature.

[0626] Referring now to FIG. 13, FIG. 113 includes an exemplary thermal ellipsoid of a shape-shifting catalyst described herein, specifically [1], prepared as a triflate salt. The thermal ellipsoid plot is presented at 50% probability level. H atoms are omitted for clarity.

[0627] Referring now to FIG. 114, FIG. 114 includes exemplary 1H NMR spectra (500 MHz,CD3CN) of the shape-shifting catalyst shown in FIG. 113.

[0628] Referring now to FIG. 115, FIG. 115 includes exemplary 1H NMR spectra (500 MHz,CD3CN) of a shape-shifting catalyst described herein, specifically [1], prepared as a hexafluoroborate salt.

[0629] Referring now to FIG. 116, FIG. 116 includes an exemplary solid-phase ATR-IRspectrum of the shape-shifting catalyst shown in FIG. 115.

[0630] Referring now to FIG. 117, FIG. 117 includes exemplary 1H NMR spectra (500 MHz,CD3CN) of a shape-shifting catalyst described herein, specifically [1], prepared as a tetrakis(3,5- bis(trifluoromethyl)phenyl)borate salt. Example 3 References

[0631] 1. Tan, C.; Zou, C.; Chen, C., Material Properties of Functional Polyethylenes fromTransition-Metal-Catalyzed Ethylene–Polar Monomer Copolymerization. Macromolecules 2022, 55 (6), 1910-1922.

[0632] 2. Chen, E. Y. X., Coordination Polymerization of Polar Vinyl Monomers by Single-SiteMetal Catalysts. Chem. Rev. 2009, 109 (11), 5157-5214.

[0633] 3. Chen, J.; Gao, Y.; Marks, T. J., Early Transition Metal Catalysis for Olefin–PolarMonomer Copolymerization. Angew. Chem. Int. Ed. 2020, 59 (35), 14726-14735.Attorney Docket No. 0073605-001022

[0634] 4. Sen, A.; Lai, T.-W.; Thomas, R. R., Reactions of electrophilic transition metal cationswith olefins and small ring compounds. Rearrangements and polymerizations. J. Organomet. Chem. 1988, 358 (1), 567-588.

[0635] 5. Williams, B. S.; Leatherman, M. D.; White, P. S.; Brookhart, M., Reactions of VinylAcetate and Vinyl Trifluoroacetate with Cationic Diimine Pd(II) and Ni(II) Alkyl Complexes:  Identification of Problems Connected with Copolymerizations of These Monomers with Ethylene. J. Am. Chem. Soc. 2005, 127 (14), 5132-5146.

[0636] 6. Chen, C., Designing catalysts for olefin polymerization and copolymerization: beyondelectronic and steric tuning. Nature Reviews Chemistry 2018, 2 (5), 6-14.

[0637] 7. Gladysz, J. A.; Ball, Z. T.; Bertrand, G.; Blum, S. A.; Dong, V. M.; Dorta, R.; Hahn,F. E.; Humphrey, M. G.; Jones, W. D.; Klosin, J.; Manners, I.; Marks, T. J.; Mayer, J. M.; Rieger, B.; Ritter, J. C.; Sattelberger, A. P.; Schomaker, J. M.; Yam, V. W.-W., Organometallics Roundtable 2011. Organometallics 2012, 31 (1), 1-18.

[0638] 8. Sipps K, Gibbs W, Sayfutyarova E, Kuo J. Shapeshifting Ligand Masks LewisAcidity of Dicationic Palladium(II). ChemRxiv. Cambridge: Cambridge Open Engage; 2023; This content is a preprint and has not been peer-reviewed.

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[0641] 11. Sen, A., Mechanistic aspects of metal-catalyzed alternating copolymerization ofolefins with carbon monoxide. Acc. Chem. Res. 1993, 26 (6), 303-310.

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[0643] 13. Rix, F. C.; Brookhart, M.; White, P. S., Mechanistic Studies of the Palladium(II)-Catalyzed Copolymerization of Ethylene with Carbon Monoxide. J. Am. Chem. Soc. 1996, 118 (20), 4746-4764.Attorney Docket No. 0073605-001022

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[0655] 25. Frankel, M. B.; Grant, L. R.; Flanagan, J. E., Historical development of glycidylazide polymer. J. Propul. Power 1992, 8 (3), 560-563.

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[0665] 35. Sykam, K.; Meka, K. K. R.; Donempudi, S., Intumescent Phosphorus and Triazole-Based Flame-Retardant Polyurethane Foams from Castor Oil. ACS Omega 2019, 4 (1), 1086-1094.

[0666] 36. Morgan, A. B.; Klatt, M., Nitrogen-Based Flame Retardants. In Non‐HalogenatedFlame Retardant Handbook, 2021; pp 236-270.Attorney Docket No. 0073605-001022

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[0673] 43. Gauthier, M.; Aridi, T., Synthesis of arborescent polystyrene by “click” grafting. J.Polym. Sci., Part A: Polym. Chem. 2019, 57 (16), 1730-1740.

[0674] 44. Eisenstein, O.; Hoffmann, R., Transition-metal complexed olefins: how theirreactivity toward a nucleophile relates to their electronic structure. J. Am. Chem. Soc. 1981, 103 (15), 4308-4320.

[0675] 45. Sen, A.; Lai, T.-W., Catalysis by solvated transition-metal cations. Novel catalytictransformations of alkenes by tetrakis(acetonitrile)palladium ditetrafluoroborate. Evidence for the formation of incipient carbonium ions as intermediates. J. Am. Chem. Soc. 1981, 103 (15), 4627- 4629.

[0676] 46. Farquhar, A. H.; Gardner, K. E.; Acosta-Calle, S.; Camp, A. M.; Chen, C.-H.; Miller,A. J. M., Cation-Controlled Olefin Isomerization Catalysis with Palladium Pincer Complexes. Organometallics 2022, 41 (22), 3366-3372.

[0677] 47. Nozaki, K.; Kusumoto, S.; Noda, S.; Kochi, T.; Chung, L. W.; Morokuma, K., WhyDid Incorporation of Acrylonitrile to a Linear Polyethylene Become Possible? Comparison of Phosphine−Sulfonate Ligand with Diphosphine and Imine−Phenolate Ligands in the Pd-Catalyzed Ethylene / Acrylonitrile Copolymerization. J. Am. Chem. Soc. 2010, 132 (45), 16030-16042.Attorney Docket No. 0073605-001022

[0678] 48. Kolthoff, I. M.; Chantooni, M. K., Protonation constants of very weak unchargedbases in acetonitrile. J. Am. Chem. Soc. 1973, 95 (26), 8539-8546.

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[0681] 51. Sakaki, S.; Maruta, K.; Ohkubo, K., Ab initio MO study of palladium-assistednucleophilic attack on a coordinated olefin: semiquantitative understanding of the reaction and the mechanism of palladium acceleration. Inorg. Chem. 1987, 26 (15), 2499-2505.

[0682] 52. Pitzer, R. M.; Lipscomb, W. N., Calculation of the Barrier to Internal Rotation inEthane. The Journal of Chemical Physics 1963, 39 (8), 1995-2004.

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[0685] 55. Burns, C. T.; Jordan, R. F., Ethylene Dimerization by Cationic Palladium(II) AlkylComplexes that Contain Bis(heterocycle)methane Ligands. Organometallics 2007, 26 (27), 6726- 6736.

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[0689] 59. Yasuda, H.; Nakano, R.; Ito, S.; Nozaki, K., Palladium / IzQO-CatalyzedCoordination–Insertion Copolymerization of Ethylene and 1,1-Disubstituted Ethylenes Bearing a Polar Functional Group. J. Am. Chem. Soc. 2018, 140 (5), 1876-1883.Attorney Docket No. 0073605-001022

[0690] 60. Hausoul, P. J. C.; Parvulescu, A. N.; Lutz, M.; Spek, A. L.; Bruijnincx, P. C. A.;Weckhuysen, B. M.; Klein Gebbink, R. J. M., Facile Access to Key Reactive Intermediates in the Pd / PR3-Catalyzed Telomerization of 1,3-Butadiene. Angew. Chem. Int. Ed. 2010, 49 (43), 7972- 7975.

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[0693] It should be understood that modifications to the embodiments disclosed herein can bemade to meet a particular set of design criteria. For instance, the number of or configuration of components or parameters may be used to meet a particular objective.

[0694] It will be apparent to those skilled in the art that numerous modifications and variationsof the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternative embodiments may include some or all the features of the various embodiments disclosed herein. For instance, it is contemplated that a particular feature described, either individually or as part of an embodiment, can be combined with other individually described features, or parts of other embodiments. The elements and acts of the various embodiments described herein can therefore be combined to provide further embodiments.

[0695] It is the intent to cover all such modifications and alternative embodiments as may comewithin the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range, including the end points. Thus, while certain exemplary embodiments of the device and methods of making and using the same have been discussed and illustrated herein, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

Claims

1. Attorney Docket No. 0073605-001022 CLAIMS1. A shapeshifting catalyst having a charge-localized state in chemical equilibrium with acharge-separated state, the shapeshifting catalyst comprising: a ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker having a length of two to five C atoms; and a transition metal cation, wherein: under the charge-localized state, the ligand coordinates to the transition metal cation in a bidentate mode through an N atom of the aromatic N-heterocycle and the alkenyl group; under the charge-separated state, the ligand coordinates to the transition metal cation in a monodentate mode; and the charge-localized state and the charge-separated state interconvert to each other through formation or dissociation of a C–N bond.

2. The shapeshifting catalyst according to claim 1, wherein the transition metal cation is acation of a metal element from Group 4, 6, 9, 10, or 11 of the periodic table.

3. The shapeshifting catalyst according to claim 1 or 2, wherein the transition metal cation is acation of Pd or Pt.

4. The shapeshifting catalyst according to any one of claims 1 or 2, wherein the transition metalcation is a divalent or multivalent cation.

5. The shapeshifting catalyst according to any one of claim 1, wherein the transition metalcation is Pd(II).

6. The shapeshifting ligand according to any one of claims 1-5, wherein the formation ordissociation of the C–N bond is accompanied by a cyclization or retrocyclization of a five- six, seven-, or eight-membered ring. Attorney Docket No. 0073605-0010227. The shapeshifting catalyst according to any one of claims 1-6, wherein the aromatic N-heterocycle comprises one or more N-heterocycles selected from a group consisting of a substituted or unsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstituted oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substituted or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted or unsubstituted tetrazine, a substituted or unsubstituted purine, and a substituted or unsubstituted pteridine, wherein the one or more N-heterocycles are optionally fused with a substituted or unsubstituted benzene, furan, pyrrole, thiophene, indole, naphthalene, anthracene, phenathrene, chryscene, or pyrene.

8. The shapeshifting catalyst according to any one of claims 1-6, wherein the aromatic N-heterocycle comprises a condensed N-heterocycle of two or more members selected from a group consisting of a substituted or unsubstituted imidazole, a substituted or unsubstituted benzimidazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted indazole, a substituted or unsubstituted oxazole, a substituted or unsubstituted benzoxazole, a Attorney Docket No. 0073605-001022 substituted or unsubstituted isoxazole, a substituted or unsubstituted benzisoxazole, a substituted or unsubstituted thiazole, a substituted or unsubstituted benzothiazole, a substituted or unsubstituted isothiazole, a substituted or unsubstituted benzisothiazole, a substituted or unsubstituted triazole, a substituted or unsubstituted benzotriazole, a substituted or unsubstituted oxodiazole, a substituted or unsubstituted benzoxadiazole, a substituted or unsubstituted thiadiazole, a substituted or unsubstituted benzothiadiazole, a substituted or unsubstituted tetrazole, a substituted or unsubstituted oxatriazole, a substituted or unsubstituted thiatriazole, a substituted or unsubstituted pentazole, a substituted or unsubstituted oxatetrazole, a substituted or unsubstituted thiatetrazole, a substituted or unsubstituted pyridine, a substituted or unsubstituted quinoline, a substituted or unsubstituted pyrazine, a substituted or unsubstituted quinoxaline, a substituted or unsubstituted naphthyridine, a substituted or unsubstituted benzodiazine, and a substituted or unsubstituted diazanaphthalene, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted quinazoline, a substituted or unsubstituted pyridazine, a substituted or unsubstituted phthalazine, a substituted or unsubstituted cinnoline, a substituted or unsubstituted triazine, a substituted or unsubstituted benzotriazine, a substituted or unsubstituted tetrazine, a substituted or unsubstituted purine, and a substituted or unsubstituted pteridine.

9. The shapeshifting catalyst according to any one of claims 1-8, wherein the aromatic N-heterocycle comprises a 14- or 18-electron π system.

10. The shapeshifting catalyst according to any one of claims 1-9, wherein one or more H atomsof the alkylene linker are each substituted by a halogen atom, a straight-chain alkyl group having 1-12 C atoms, a branched or cyclic alkyl group having 3-12 C atoms, an alkenyl or alkynyl group having 2-12 C atoms, or an aryl group having 6-12 C atoms.

11. The shapeshifting catalyst according to claim 10, wherein one or more H atoms of thealkylene linker are each substituted by a methyl group.

12. The shapeshifting catalyst according to any one of claims 1-11, wherein one or more H atomsof the alkenyl group is substituted by a halogen atom, a straight-chain alkyl group having 1- Attorney Docket No. 0073605-001022 12 C atoms, a branched or cyclic alkyl group having 3-12 C atoms, an alkenyl or alkynyl group having 2-12 C atoms, or an aryl group having 6-12 C atoms.

13. The shapeshifting catalyst according to claim 12, wherein one or more H atoms of thealkenyl group is substituted by a -C6H4-C(CH3)3group.

14. The shapeshifting catalyst according to any one of claims 1-13, further comprising one ormore labile ligands coordinated to the transition metal cation.

15. The shapeshifting catalyst according to claim 14, wherein at least one labile ligand of the oneor more labile ligands comprises acetonitrile.

16. The shapeshifting catalyst according to any one of claims 1-15, wherein the shapeshiftingcatalyst is a BF4- salt, a PF6- salt, a CF3SO3- salt, or a [{3,5-(CF3)2C6H3}4B]- salt of a cationic coordination complex.

17. The shapeshifting catalyst according to any one of claims 1-16, wherein the transition metalcation has a coordination number of four or six.

18. The shapeshifting catalyst according to any one of claims 1-17, wherein the transition metalcation has a square planar or octahedral coordination geometry.

19. The shapeshifting catalyst according to any one of claims 1-18, wherein the charge-separatedstate has a Gibbs free energy that is lower than that of the charge-localized state by no more than 30 kcal mol-1.

20. The shapeshifting catalyst according to any one of claims 1-19, wherein both the charge-localized state and the charge-separated state are catalytically active.

21. The shapeshifting catalyst according to any one of claims 1-20, wherein only the charge-localized state is catalytically active. Attorney Docket No. 0073605-00102222. A shapeshifting catalyst having an electrophilic state in chemical equilibrium with anucleophilic state, the shapeshifting catalyst comprising: a ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker having a length of two to five C atoms; and a transition metal cation, wherein: under the electrophilic state, the ligand coordinates to the transition metal cation in a bidentate mode through one or more N atoms of the aromatic N-heterocycle and the alkenyl group; under the nucleophilic state, the ligand coordinates to the transition metal cation in a monodentate mode; and the electrophilic state and the nucleophilic state interconvert to one another through formation or dissociation of a C–N bond.

23. A shapeshifting catalyst having an unmasked Lewis acidic state in chemical equilibrium witha masked Lewis acidic state, the shapeshifting catalyst comprising: a ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker having a length of two to five C atoms; and a transition metal cation, wherein: under the unmasked Lewis acidic state, the ligand coordinates to the transition metal cation in a bidentate mode through one or more N atoms of the aromatic N- heterocycle and the alkenyl group; under the masked Lewis acidic state, the ligand coordinates to the transition metal cation in a monodentate mode; and the unmasked Lewis acidic state and the masked Lewis acidic state interconvert to one another through formation or dissociation of a C–N bond. Attorney Docket No. 0073605-00102224. A method of preparing the shapeshifting catalyst according to any one of claims 1-23,comprising metalating the ligand using a salt or coordination complex of the transition metal cation.

25. A method of using the shapeshifting catalyst according to any one of claims 1-24,comprising: providing a catalytically active amount of the shapeshifting catalyst to one or more organic substrates; and transforming the one or more organic substrates into one or more products.

26. The method according to claim 25, wherein the one or more organic substrates areunsaturated.

27. The method according to claim 25 or 26, wherein at least one organic substrate of the one ormore organic substrates is an unsubstituted or substituted olefin or styrene.

28. The method according to any one of claims 25-27, wherein the at least one organic substrateor the one or more substrates comprises a polar functional group.

29. The method according to claim 28, wherein the polar functional group is selected from a listconsisting of an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester, a sulfonate ester, a sulfonate ion, a halogen, and a pyridinyl group.

30. The method according to any one of claims 25-29, further comprising:exposing the one or more organic substrates to the shapeshifting catalyst to facilitate a polymerization reaction, thereby producing a polymeric product.

31. The method according to claim 30, wherein the polymeric product comprises polystyrene,polyethylene, or polypropylene. Attorney Docket No. 0073605-00102232. The method according to claim 30 or 31, wherein the polymeric product comprises acopolymer, wherein optionally at least one monomer of the copolymer comprises a polar functional group.

33. The method according to any one of claims 30-32, wherein the charge-separated state istolerant of polar functional groups or both the charge-localized state and the charge-separated state are tolerant of polar functional groups.

34. Use of the shapeshifting catalyst according to any one of claims 1-23 in an isomerization,oligomerization, telomerization, or polymerization reaction.

35. An article of manufacture comprising the shapeshifting catalyst according to any one ofclaims 1-23.

36. A method of stabilizing a Lewis-acidic catalyst, comprising:coordinating a ligand to a transition metal cation of a Lewis-acidic catalyst, the ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker having a length of two to five C atoms, wherein: under the charge-localized state, the ligand coordinates to the transition metal cation in a bidentate mode through an N atom of the aromatic N-heterocycle and the alkenyl group; under the charge-separated state, the ligand coordinates to the transition metal cation in a monodentate mode; and the charge-localized state and the charge-separated state interconvert to each other through formation or dissociation of a C–N bond.

37. A method of making a polymeric material, comprising:providing a catalytically active amount of a shapeshifting catalyst, the shapeshifting catalyst comprising: a ligand having i) an aromatic N-heterocycle and ii) an alkenyl group covalently connected to the aromatic N-heterocycle through an alkylene linker having a length of two to five C atoms; and Attorney Docket No. 0073605-001022 a transition metal cation, wherein: under a charge-localized state, the ligand coordinates to the transition metal cation in a bidentate mode through one or more N atoms of the aromatic N-heterocycle and the alkenyl group; under a charge-separated state, the ligand coordinates to the transition metal cation in a monodentate mode; and the charge-localized state and the charge-separated state interconvert to one another through formation or dissociation of a C–N bond; and contacting the shapeshifting catalyst with one or more organic substrates to produce a polymeric product.

38. The method according to claim 37, wherein the polymeric product comprises polystyrene,polyethylene, or polypropylene.

39. The method according to claim 37 or 38, wherein the polymeric product comprises acopolymer, wherein optionally at least one monomer of the copolymer comprises a polar functional group.

40. The method according to any one of claims 37-39, wherein the charge-separated state istolerant of polar functional groups or both the charge-localized state and the charge-separated state are tolerant of polar functional groups.

41. The method according to any one of claims 39-40, wherein the polar functional group isselected from a list consisting of an alcohol, a phenol, an ether, a thiol, an amine, an amide, a nitrile, a carbonyl, a ketone, an aldehyde, a carboxyl, an ester, s sulfonate ester, a sulfonate ion, a halogen, and a pyridinyl group.

42. The method according to any one of claims 37-41, wherein the one or more organicsubstrates are unsaturated. Attorney Docket No. 0073605-00102243. The method according to any one of claims 37-42, wherein at least one organic substrate ofthe one or more organic substrates is an unsubstituted or substituted olefin or styrene.

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