Pincer-ligated cobalt catalysts and methods of making and using thereof

Abstract

Desribed herein are catalytic metal complexes as well as methods of making and using thereof.

Description

[0001] Attorney Docket No.103361-532WO1 Pincer-Ligated Cobalt Catalysts and Methods of Making and Using Thereof CROSS-REFERENCE TO RELATED APPLICATIONS This application claims benefit of priority of U.S. Provisional Application No. 63 / 525,668, filed July 8, 2023, which is hereby incorporated herein by reference in its entirety. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with government support under Grant / Contract No.2101002 awarded by the National Science Foundation. The government has certain rights in the invention. BACKGROUND For decades, many organic transformations, such as hydrogenation reactions, have relied on precious metal catalysts. However, the low abundance, high price, and inherent toxicity of precious metals have led to intense interest in developing earth-abundant metal catalysts. Significant progress has been made in recent years on the development of base metal catalysts. For example, single-site hydrogenation catalysts based on iron, cobalt, nickel, or copper coordinated with sterically encumbered strong field nitrogen- or phosphorus-donor ligands have been reported. However, each of these homogeneous base metal catalysts typically only hydrogenates a narrow class of substrates with limited turnover numbers. Accordingly, there remains a need to develop improved catalysts for a wide variety of applications. SUMMARY Transition metal-catalyzed hydroelementation reactions are used to add H-E (E = H, Si, B, for example) across C-C double bonds. Alkene hydrogenation reactions are widely used in the chemical industry to convert alkenes and aromatics into value-added saturated products in the petrochemical, pharmaceutical, agrochemical, and food industries. Alkene hydrofunctionalization reactions including hydroboration and hydrosilylation provide well- established routes to incorporate reactive functional groups into hydrocarbon feedstocks. The value of alkene hydrosilylation lies in its bulk application in the industrial silicone industry, and Attorney Docket No.103361-532WO1 alkene hydroboration provides a straightforward method to prepare boronate esters that are versatile synthons to construct more elaborate molecules in the fine chemical industry. Many precious metal (e.g. rhodium, iridium, palladium, platinum) catalysts have been developed for such hydrofunctionalization reactions, but the application of catalysts featuring Earth abundant transition metals in these transformations has only recently been realized. The low cost and greater availability of the late first row transition metals such as cobalt render them desirable targets in sustainable catalyst design, with the hopes that they can replace precious metals or even provide access to new reaction space inaccessible to precious metals. One of the primary challenges in the development of Earth-abundant metal catalysts is developing strategies to promote the two-electron processes that are essential to many catalytic cycles. Ligand design plays a central role in addressing this challenge, often by providing a sufficiently electron-rich and strong field ligand environment to stabilize low spin electron configurations and promote metal-centered two-electron redox changes. Described herein are catalysts that employ a family of tridentate pincer ligands featuring a central N-heterocyclic phosphinite fragment and two appended phosphine sidearms. These ligands can be readily synthesized (e.g., in 4 steps) from commercially available precursors in high yields and with simple separation and purification procedures. The ligands can then be coordinated to metals (e.g., rhodium, iridium, cobalt, or iron) in a single step to afford catalytic metal complexes, including (PPR1P)MX2complexes, where M is Rh, Ir, Co, or Fe, X is an anionic ligand (e.g., a halide such as Cl, Br, or I, a hydride, or alkyl), and R1is hydrogen, alkyl, haloalkyl, alkoxy, amino, alkylamino, or dialkylamino. This family of complexes, in the presence of an activator such as KBEt3H, are promising and highly active catalysts for the hydrogenation, hydroboration, and hydrosilylation of alkenes. By way of example, described herein is a synthetic protocol for (PPOiPrP)CoI2. This complex was fully characterized both structurally and spectroscopically using single crystal X- ray diffraction, UV-visible spectroscopy, and NMR spectroscopy. This compound was found to be a highly active catalyst for the hydroboration and hydrogenation of alkenes. In initial tests of this catalytic system, it was active towards a variety of challenging substrates such 1,1’- disubstituted alkenes and internal alkenes and tolerant to a wide range of functional groups. The catalyst operates under mild conditions, achieving complete conversion with most substrates tested within several hours at room temperature and under ambient pressure (1 atm of H2 for the hydrogenation case). While most substrate screenings were conducted using a 0.5 mol % catalyst loading, we even lower catalyst loadings were explored for the hydroboration reaction and achieved complete conversion of styrene to a 95:5 ratio of linear:branched hydroboration Attorney Docket No.103361-532WO1 products in 3 hours with 0.2 mol% catalyst loading. Moreover, the catalyst remained active after all substrate has been consumed, such that a reaction that has reached 100% conversion can be recharged with additional substrate and the catalyst will continue to operate until complete conversion has again been reached. Thus far, these recharge experiments have been repeated up to 3 times with no loss in catalytic activity. Lastly, in contrast to many Earth-abundant transition metal catalysts, particularly those with phosphines, the catalytic systems described herein are relatively tolerant to adventitious exposure to air and moisture. The catalyst itself is relatively resistant to decomposition in air and can be weighed out on the benchtop. The stability of these precatalyst presents a notable advantage and increases the applicability and versatility of this catalyst system. Further, the synthetic protocol described herein is amenable to easy modifications of the P-OR substituent on the central phosphorus atom, permitting facile steric and electronic modifications to the catalyst. This provides access to even more active and efficient catalysts than (PPOiPrP)CoI2. This is especially important for hydrosilylation and hydroboration reactions, for which there are two possible products (linear and branched). The synthetic pathways described herein also allow for the incorporation of chiral functional groups via the incorporation of chiral alcohols into the central P-OR position. This provides the opportunity to prepare catalysts which exhibit enantioselective activity. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III below Attorney Docket No.103361-532WO1 Formula III wherein M is rhodium, iridium, cobalt, or iron; X is, individually for each occurrence, an anionic ligand; Y represents an alkene ligand; R1represents hydrogen, alkyl, haloalkyl, ORA, or NRA2; R2and R2’represent, individually for each occurrence, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted with one or more substituents individually chosen from RB; or R2and R2′, together with the atoms to which they are attached, combine to form a 3 to 7 membered ring optionally substituted with one or more substituents individually chosen from RB; R3, R4, R5, and R6represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; R7, R7’, R8, and R8’represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, Attorney Docket No.103361-532WO1 haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; RArepresents, individually for each occurrence, hydrogen, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; and RBrepresents, individually for each occurrence, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, and heterodialkylaminocarbonyl. In some aspects, the complex is defined by Formula I. In some aspects, the complex is defined by Formula II. In some aspects, the complex is defined by Formula III. In certain aspects of Formula III, the complex is defined by the formula below wherein M is rhodium, iridium, cobalt, or iron; X is, individually for each occurrence, an anionic ligand; R1represents hydrogen, alkyl, haloalkyl, ORA, or NRA2; R2and R2’represent, individually for each occurrence, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted with one or more substituents individually chosen from RB; or R2and R2′, together with the Attorney Docket No.103361-532WO1 atoms to which they are attached, combine to form a 3 to 7 membered ring optionally substituted with one or more substituents individually chosen from RB; R3, R4, R5, and R6represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; R7, R7’, R8, and R8’represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; RArepresents, individually for each occurrence, hydrogen, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; RBrepresents, individually for each occurrence, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, and heterodialkylaminocarbonyl; and RCand RC’individually represent hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB. In certain aspects of Formula III, Y represents styrene. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein M is rhodium. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein M is iridium. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein M is cobalt. In some aspects, the Attorney Docket No.103361-532WO1 techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein M is iron. In some aspects of Formula I, M is cobalt or iron. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R3, R4, R5, and R6represent hydrogen. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R7, R7’, R8, and R8’represent hydrogen. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R3, R4, R5, R6, R7, R7’, R8, and R8’represent hydrogen. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R2and R2’represent, individually for each occurrence, alkyl, aryl, cycloalkyl, alkylaryl, or alkylcycloalkyl, each optionally substituted with one or more substituents individually chosen from RB. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R2and R2’represent, individually for each occurrence, alkyl or aryl, each optionally substituted with one or more substituents individually chosen from RB. In certain aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R2and R2’represent, individually for each occurrence, a C1-C6 alkyl group (e.g., an isopropyl group or a tert-butyl group). In certain aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R2and R2’represent, individually for each occurrence, an aryl group (e.g., a phenyl group). In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R1represents an electron withdrawing group. In certain aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R1represents a haloalkyl group (e.g., a trifluoromethyl group). In certain aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R1represents an alkoxy or haloalkoxy group. In some aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein X represents halogen (e.g., I or Cl). In other aspects, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein X represents hydride or alkyl. In certain aspects, the techniques described herein relate to a metal complex shown below Attorney Docket No.103361-532WO1 .Also described herein are methods of using the metal complexes described herein as catalysts, for example, for hydroelementation of an olefin. In certain embodiments, the metal complexes described herein as catalysts, for example, in a hydrogenation reaction, a hydroboration reaction, or a hydrosilylation reaction. Attorney Docket No.103361-532WO1 DESCRIPTION OF DRAWINGS Figure 1 shows a displacement ellipsoid (50%) representation of 1. For clarity, all hydrogen atoms except for the P−H moiety, disorder of the amine backbone, and a dichloromethane molecule have been omitted. Relevant interatomic distances (A): Co1−P1: 2.0842(16), Co1−P2: 2.2177(17), Co1−P3: 2.2283 (17), P1−H1: 1.31(4), P1−N1: 1.680(5), P1−N2: 1.705(5). Figure 2 schematically illustrates the catalytic activity of an example Co(II) catalyst. Figure 3 illustrates a general synthetic protocol that can be used to prepare example complexes described herein. Figure 4 illustrates a general synthetic protocol that can be used to prepare example complexes described herein. Figure 5 illustrates a selection of pincer-ligated cobalt complexes with high activity for the hydroboration of alkenes. Figure 6 shows a displacement ellipsoid (50%) representation of PPCF3PCoI2. Figure 7 illustrates the results of catalytic condition optimization.aConversion was determined by GCMS-FID. Yields given in parenthesis are isolated yields after column chromatography. Figure 8 shows a proposed mechanism for hydroboration catalyzed by an example complex described herein. DETAILED DESCRIPTION Definitions 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. Methods and materials are described herein for use in the present invention; other, suitable methods and materials known in the art can also be used. The materials, methods, and examples are illustrative only and not intended to be limiting. All publications, patent applications, patents, sequences, database entries, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. At various places in the present specification, divalent linking substituents are described. Where the structure clearly requires a linking group, the Markush variables listed for that group are understood to be linking groups. Attorney Docket No.103361-532WO1 The term “n-membered” where n is an integer typically describes the number of ring- forming atoms in a moiety where the number of ring-forming atoms is n. For example, piperidinyl is an example of a 6-membered heterocycloalkyl ring, pyrazolyl is an example of a 5-membered heteroaryl ring, pyridyl is an example of a 6-membered heteroaryl ring, and 1,2,3,4-tetrahydro-naphthalene is an example of a 10-membered cycloalkyl group. As used herein, the phrase “optionally substituted” means unsubstituted or substituted. As used herein, the term “substituted” means that a hydrogen atom is removed and replaced by a substituent. It is to be understood that substitution at a given atom is limited by valency. Throughout the definitions, the term “Cn-m” indicates a range which includes the endpoints, wherein n and m are integers and indicate the number of carbons. Examples include C1-4, C1-6, and the like. As used herein, the term “Cn-malkyl”, employed alone or in combination with other terms, refers to a saturated hydrocarbon group that may be straight-chain or branched, having n to m carbons. Examples of alkyl moieties include, but are not limited to, chemical groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, sec-butyl; higher homologs such as 2-methyl-1-butyl, n-pentyl, 3-pentyl, n-hexyl, 1,2,2-trimethylpropyl, and the like. In some embodiments, the alkyl group contains from 1 to 6 carbon atoms, from 1 to 4 carbon atoms, from 1 to 3 carbon atoms, or 1 to 2 carbon atoms. As used herein, “Cn-malkenyl” refers to an alkyl group having one or more double carbon-carbon bonds and having n to m carbons. Example alkenyl groups include, but are not limited to, ethenyl, n-propenyl, isopropenyl, n-butenyl, sec-butenyl, and the like. In some embodiments, the alkenyl moiety contains 2 to 6, 2 to 4, or 2 to 3 carbon atoms. As used herein, “Cn-malkynyl” refers to an alkyl group having one or more triple carbon- carbon bonds and having n to m carbons. Example alkynyl groups include, but are not limited to, ethynyl, propyn-1-yl, propyn-2-yl, and the like. In some embodiments, the alkynyl moiety contains 2 to 6, 2 to 4, or 2 to 3 carbon atoms. As used herein, the term “Cn-m alkylene”, employed alone or in combination with other terms, refers to a divalent alkyl linking group having n to m carbons. Examples of alkylene groups include, but are not limited to, ethan-1,2-diyl, propan-1,3-diyl, propan-1,2-diyl, butan- 1,4-diyl, butan-1,3-diyl, butan-1,2-diyl, 2-methyl-propan-1,3-diyl, and the like. In some embodiments, the alkylene moiety contains 2 to 6, 2 to 4, 2 to 3, 1 to 6, 1 to 4, or 1 to 2 carbon atoms. As used herein, the term “Cn-malkoxy”, employed alone or in combination with other terms, refers to a group of formula -O-alkyl, wherein the alkyl group has n to m carbons. Attorney Docket No.103361-532WO1 Example alkoxy groups include methoxy, ethoxy, propoxy (e.g., n-propoxy and isopropoxy), tert-butoxy, and the like. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “Cn-m alkylamino” refers to a group of formula -NH(alkyl), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “Cn-m alkoxycarbonyl” refers to a group of formula -C(O)O- alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “Cn-malkylcarbonyl” refers to a group of formula -C(O)-alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “Cn-malkylcarbonylamino” refers to a group of formula -NHC(O)-alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “Cn-malkylsulfonylamino” refers to a group of formula -NHS(O)2-alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “aminosulfonyl” refers to a group of formula -S(O)2NH2. As used herein, the term “Cn-malkylaminosulfonyl” refers to a group of formula -S(O)2NH(alkyl), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “di(Cn-malkyl)aminosulfonyl” refers to a group of formula -S(O)2N(alkyl)2, wherein each alkyl group independently has n to m carbon atoms. In some embodiments, each alkyl group has, independently, 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “aminosulfonylamino” refers to a group of formula - NHS(O)2NH2. As used herein, the term “Cn-m alkylaminosulfonylamino” refers to a group of formula - NHS(O)2NH(alkyl), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “di(Cn-m alkyl)aminosulfonylamino” refers to a group of formula -NHS(O)2N(alkyl)2, wherein each alkyl group independently has n to m carbon atoms. In some embodiments, each alkyl group has, independently, 1 to 6, 1 to 4, or 1 to 3 carbon atoms. Attorney Docket No.103361-532WO1 As used herein, the term “aminocarbonylamino”, employed alone or in combination with other terms, refers to a group of formula -NHC(O)NH2. As used herein, the term “Cn-malkylaminocarbonylamino” refers to a group of formula - NHC(O)NH(alkyl), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “di(Cn-malkyl)aminocarbonylamino” refers to a group of formula -NHC(O)N(alkyl)2, wherein each alkyl group independently has n to m carbon atoms. In some embodiments, each alkyl group has, independently, 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “Cn-malkylcarbamyl” refers to a group of formula -C(O)- NH(alkyl), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “thio” refers to a group of formula -SH. As used herein, the term “Cn-m alkylsulfinyl” refers to a group of formula -S(O)-alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “Cn-m alkylsulfonyl” refers to a group of formula -S(O)2-alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “amino” refers to a group of formula –NH2. As used herein, the term "aryl," employed alone or in combination with other terms, refers to an aromatic hydrocarbon group, which may be monocyclic or polycyclic (e.g., having 2, 3 or 4 fused rings). The term "Cn-maryl" refers to an aryl group having from n to m ring carbon atoms. Aryl groups include, e.g., phenyl, naphthyl, anthracenyl, phenanthrenyl, indanyl, indenyl, and the like. In some embodiments, aryl groups have from 6 to about 20 carbon atoms, from 6 to about 15 carbon atoms, or from 6 to about 10 carbon atoms. In some embodiments, the aryl group is a substituted or unsubstituted phenyl. As used herein, the term “carbamyl” to a group of formula –C(O)NH2. As used herein, the term “carbonyl”, employed alone or in combination with other terms, refers to a -C(=O)- group, which may also be written as C(O). As used herein, the term “di(Cn-m-alkyl)amino” refers to a group of formula -N(alkyl)2, wherein the two alkyl groups each has, independently, n to m carbon atoms. In some embodiments, each alkyl group independently has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. Attorney Docket No.103361-532WO1 As used herein, the term “di(Cn-m-alkyl)carbamyl” refers to a group of formula – C(O)N(alkyl)2, wherein the two alkyl groups each has, independently, n to m carbon atoms. In some embodiments, each alkyl group independently has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “halo” refers to F, Cl, Br, or I. In some embodiments, a halo is F, Cl, or Br. In some embodiments, a halo is F or Cl. As used herein, “Cn-mhaloalkoxy” refers to a group of formula –O-haloalkyl having n to m carbon atoms. An example haloalkoxy group is OCF3. In some embodiments, the haloalkoxy group is fluorinated only. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “Cn-mhaloalkyl”, employed alone or in combination with other terms, refers to an alkyl group having from one halogen atom to 2s+1 halogen atoms which may be the same or different, where “s” is the number of carbon atoms in the alkyl group, wherein the alkyl group has n to m carbon atoms. In some embodiments, the haloalkyl group is fluorinated only. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, “cycloalkyl” refers to non-aromatic cyclic hydrocarbons including cyclized alkyl and / or alkenyl groups. Cycloalkyl groups can include mono- or polycyclic (e.g., having 2, 3 or 4 fused rings) groups and spirocycles. Cycloalkyl groups can have 3, 4, 5, 6, 7, 8, 9, or 10 ring-forming carbons (C3-10). Ring-forming carbon atoms of a cycloalkyl group can be optionally substituted by oxo or sulfido (e.g., C(O) or C(S)). Cycloalkyl groups also include cycloalkylidenes. Example cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopentenyl, cyclohexenyl, cyclohexadienyl, cycloheptatrienyl, norbornyl, norpinyl, norcarnyl, and the like. In some embodiments, cycloalkyl is cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopentyl, or adamantyl. In some embodiments, the cycloalkyl has 6-10 ring-forming carbon atoms. In some embodiments, cycloalkyl is adamantyl. Also included in the definition of cycloalkyl are moieties that have one or more aromatic rings fused (i.e., having a bond in common with) to the cycloalkyl ring, for example, benzo or thienyl derivatives of cyclopentane, cyclohexane, and the like. A cycloalkyl group containing a fused aromatic ring can be attached through any ring-forming atom including a ring-forming atom of the fused aromatic ring. As used herein, “heteroaryl” refers to a monocyclic or polycyclic aromatic heterocycle having at least one heteroatom ring member selected from sulfur, oxygen, and nitrogen. In some embodiments, the heteroaryl ring has 1, 2, 3, or 4 heteroatom ring members independently selected from nitrogen, sulfur and oxygen. In some embodiments, any ring-forming N in a Attorney Docket No.103361-532WO1 heteroaryl moiety can be an N-oxide. In some embodiments, the heteroaryl has 5-10 ring atoms and 1, 2, 3 or 4 heteroatom ring members independently selected from nitrogen, sulfur and oxygen. In some embodiments, the heteroaryl has 5-6 ring atoms and 1 or 2 heteroatom ring members independently selected from nitrogen, sulfur and oxygen. In some embodiments, the heteroaryl is a five-membered or six-membereted heteroaryl ring. A five-membered heteroaryl ring is a heteroaryl with a ring having five ring atoms wherein one or more (e.g., 1, 2, or 3) ring atoms are independently selected from N, O, and S. Exemplary five-membered ring heteroaryls are thienyl, furyl, pyrrolyl, imidazolyl, thiazolyl, oxazolyl, pyrazolyl, isothiazolyl, isoxazolyl, 1,2,3-triazolyl, tetrazolyl, 1,2,3-thiadiazolyl, 1,2,3-oxadiazolyl, 1,2,4-triazolyl, 1,2,4- thiadiazolyl, 1,2,4-oxadiazolyl, 1,3,4-triazolyl, 1,3,4-thiadiazolyl, and 1,3,4-oxadiazolyl. A six- membered heteroaryl ring is a heteroaryl with a ring having six ring atoms wherein one or more (e.g., 1, 2, or 3) ring atoms are independently selected from N, O, and S. Exemplary six- membered ring heteroaryls are pyridyl, pyrazinyl, pyrimidinyl, triazinyl and pyridazinyl. As used herein, “heterocycloalkyl” refers to non-aromatic monocyclic or polycyclic heterocycles having one or more ring-forming heteroatoms selected from O, N, or S. Included in heterocycloalkyl are monocyclic 4-, 5-, 6-, and 7-membered heterocycloalkyl groups. Heterocycloalkyl groups can also include spirocycles. Example heterocycloalkyl groups include pyrrolidin-2-one, 1,3-isoxazolidin-2-one, pyranyl, tetrahydropuran, oxetanyl, azetidinyl, morpholino, thiomorpholino, piperazinyl, tetrahydrofuranyl, tetrahydrothienyl, piperidinyl, pyrrolidinyl, isoxazolidinyl, isothiazolidinyl, pyrazolidinyl, oxazolidinyl, thiazolidinyl, imidazolidinyl, azepanyl, benzazapene, and the like. Ring-forming carbon atoms and heteroatoms of a heterocycloalkyl group can be optionally substituted by oxo or sulfido (e.g., C(O), S(O), C(S), or S(O)2, etc.). The heterocycloalkyl group can be attached through a ring- forming carbon atom or a ring-forming heteroatom. In some embodiments, the heterocycloalkyl group contains 0 to 3 double bonds. In some embodiments, the heterocycloalkyl group contains 0 to 2 double bonds. Also included in the definition of heterocycloalkyl are moieties that have one or more aromatic rings fused (i.e., having a bond in common with) to the cycloalkyl ring, for example, benzo or thienyl derivatives of piperidine, morpholine, azepine, etc. A heterocycloalkyl group containing a fused aromatic ring can be attached through any ring- forming atom including a ring-forming atom of the fused aromatic ring. In some embodiments, the heterocycloalkyl has 4-10, 4-7 or 4-6 ring atoms with 1 or 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur and having one or more oxidized ring members. At certain places, the definitions or embodiments refer to specific rings (e.g., an azetidine ring, a pyridine ring, etc.). Unless otherwise indicated, these rings can be attached to any ring Attorney Docket No.103361-532WO1 member provided that the valency of the atom is not exceeded. For example, an azetidine ring may be attached at any position of the ring, whereas a pyridin-3-yl ring is attached at the 3- position. The expressions, “ambient temperature” and “room temperature” or “rt” as used herein, are understood in the art, and refer generally to a temperature, e.g. a reaction temperature, that is about the temperature of the room in which the reaction is carried out, for example, a temperature from about 20 ºC to about 30 ºC. The term “halogen,” as used herein, means an element selected from fluorine, chlorine, bromine, and iodine. The term “anionic ligand,” as used herein, refers to a substituent capable of coordinating with a metallic centre, having a charge capable of partial or complete compensation of a metallic centre charge. Examples of anionic ligands include but are not limited to fluoride, chloride, bromide, iodide, hydride, alkyl, alkoxide, triflate, thiocyanate anions, anions of carboxylic acids (e.g., acetate), anions of alcohols and phenols, anions of thiols and thiophenols, anions of hydrocarbons with a delocalized charge (e.g. a cyclopentadiene anion), anions of (organo)sulfuric acids and of (organo)phosphoric acids and esters thereof (such as e.g. anions of alkylosulfonic acids and of arylosulphonic acids, anions of alkylophosphoric acids and of arylophosphoric acids, anions of alkyl and aryl esters of sulfuric acid, anions of alkyl and aryl esters of phosphoric acids, anions of alkyl and aryl esters of alkylphosphoric and arylphosphoric acids). Metal Complexes Provided herein are metal complex defined by Formula I, Formula II, or Formula III below Attorney Docket No.103361-532WO1 Formula III wherein M is rhodium, iridium, cobalt, or iron; X is, individually for each occurrence, an anionic ligand; Y represents an alkene ligand; R1represents hydrogen, alkyl, haloalkyl, ORA, or NRA2; R2and R2’represent, individually for each occurrence, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted with one or more substituents individually chosen from RB; or R2and R2′, together with the atoms to which they are attached, combine to form a 3 to 7 membered ring optionally substituted with one or more substituents individually chosen from RB; R3, R4, R5, and R6represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; R7, R7’, R8, and R8’represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, Attorney Docket No.103361-532WO1 haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; RArepresents, individually for each occurrence, hydrogen, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; and RBrepresents, individually for each occurrence, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, and heterodialkylaminocarbonyl. In some examples, the complex is defined by Formula I. In some examples, the complex is defined by Formula II. In some examples, the complex is defined by Formula III. In certain examples of Formula III, the complex is defined by the formula below wherein M is rhodium, iridium, cobalt, or iron; X is, individually for each occurrence, an anionic ligand; R1represents hydrogen, alkyl, haloalkyl, ORA, or NRA2; R2and R2’represent, individually for each occurrence, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted with one or more substituents individually chosen from RB; or R2and R2′, together with the Attorney Docket No.103361-532WO1 atoms to which they are attached, combine to form a 3 to 7 membered ring optionally substituted with one or more substituents individually chosen from RB; R3, R4, R5, and R6represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; R7, R7’, R8, and R8’represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; RArepresents, individually for each occurrence, hydrogen, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; RBrepresents, individually for each occurrence, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, and heterodialkylaminocarbonyl; and RCand RC’individually represent hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB. In certain examples of Formula III, Y represents styrene. In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein M is rhodium. In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein M is iridium. In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein M is cobalt. In some Attorney Docket No.103361-532WO1 examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein M is iron. In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R3, R4, R5, and R6represent hydrogen. In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R7, R7’, R8, and R8’represent hydrogen. In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R3, R4, R5, R6, R7, R7’, R8, and R8’represent hydrogen. In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R2and R2’represent, individually for each occurrence, alkyl, aryl, cycloalkyl, alkylaryl, or alkylcycloalkyl, each optionally substituted with one or more substituents individually chosen from RB. In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R2and R2’represent, individually for each occurrence, alkyl or aryl, each optionally substituted with one or more substituents individually chosen from RB. In certain examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R2and R2’represent, individually for each occurrence, a C1-C6 alkyl group (e.g., an isopropyl group or a tert-butyl group). In certain examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R2and R2’represent, individually for each occurrence, an aryl group (e.g., a phenyl group). In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R1represents an electron withdrawing group. In certain examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R1represents a haloalkyl group (e.g., a trifluoromethyl group). In certain examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein R1represents an alkoxy or haloalkoxy group. In some examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein X represents halogen (e.g., I or Cl). In other examples, the techniques described herein relate to a metal complex defined by Formula I, Formula II, or Formula III, wherein X represents hydride or alkyl. Attorney Docket No.103361-532WO1 In certain examples, the techniques described herein relate to a metal complex shown below .

[0002] Attorney Docket No.103361-532WO1 In certain examples, the techniques described herein relate to a metal complex shown below .

[0003] Attorney Docket No.103361-532WO1 In certain examples, the techniques described herein relate to a metal complex shown below .

[0004] Attorney Docket No.103361-532WO1 In certain examples, the techniques described herein relate to a metal complex shown below .Synthesis The complexes described herein can be prepared using synthetic methodologies known in the art. By way of example, representative complexes described herein can be prepared using the synthetic strategy outlined in the scheme below. Attorney Docket No.103361-532WO1 It will be appreciated by one skilled in the art that the processes described are not the exclusive means by which complexes provided herein may be synthesized and that a broad repertoire of synthetic organic reactions is available to be potentially employed in synthesizing the ligands and complexes provided herein. The person skilled in the art knows how to select and implement appropriate synthetic routes. Suitable synthetic methods of starting materials, intermediates and products may be identified by reference to the literature. The reactions for preparing complexes described herein can be carried out in suitable solvents which can be readily selected by one of skill in the art of organic synthesis. Suitable solvents can be substantially non-reactive with the starting materials (reactants), the intermediates, or products at the temperatures at which the reactions are carried out, (e.g., temperatures which can range from the solvent's freezing temperature to the solvent's boiling temperature). A given reaction can be carried out in one solvent or a mixture of more than one solvent. Depending on the particular reaction step, suitable solvents for a particular reaction step can be selected by the skilled artisan. Preparation of complexes described herein can involve the protection and deprotection of various chemical groups. The need for protection and deprotection, and the selection of appropriate protecting groups, can be readily determined by one skilled in the art. The chemistry of protecting groups can be found, for example, in T. W. Greene and P. G. M. Wuts, Protective Groups in Organic Synthesis, 3rdEd., Wiley & Sons, Inc., New York (1999). Reactions can be monitored according to any suitable method known in the art. For example, product formation can be monitored by spectroscopic means, such as nuclear magnetic resonance spectroscopy (e.g.,1H,13C, or31P), infrared spectroscopy, spectrophotometry (e.g., UV-visible), mass spectrometry, or by chromatographic methods such as high-performance Attorney Docket No.103361-532WO1 liquid chromatography (HPLC), liquid chromatography-mass spectroscopy (LCMS), or thin layer chromatography (TLC). Complexes can be purified by those skilled in the art by a variety of methods, including high performance liquid chromatography (HPLC), crystallization, and normal phase silica chromatography. Methods of Use Also described herein are methods of using the metal complexes described herein as catalysts, for example, for hydroelementation of an olefin. In certain embodiments, the metal complexes described herein as catalysts, for example, in a hydrogenation reaction, a hydroboration reaction, or a hydrosilylation reaction. EXAMPLES The invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of non-critical parameters which can be changed or modified to yield essentially the same results. Example 1. Catalytic Hydrogenation of Terminal Alkenes by a (PPP) Pincer-Ligated Cobalt(II) Complex. Summary A Co(II) complex, (PPHP)CoI2, was synthesized and evaluated as a precatalyst for the hydrogenation of terminal alkenes under mild conditions (1 atm H2, ambient temperature) using KBEt3H as an activator. This catalytic system was found to be active for terminal alkene substrates, including 1,1′-disubstituted alkenes, and to exhibit modest air and moisture stability. A preliminary investigation into substrate scope and functional group tolerance was performed. Upon the completion of catalytic reactions, the sole metal complex observed was identified as the dimeric species [(PPP)CoH]2 suggesting that the catalytically active species may be a cobalt hydride monomer. Introduction The catalytic hydrogenation of unsaturated C−E (E = C, O, N) bonds by homogeneous transition metal complexes has been extensively studied, predominately using complexes that feature precious transition metals. These complexes have been iteratively improved in their catalytic activities and functional group tolerances via detailed structure / activity correlation studies into the influence of different metal centers and ligand environments on catalytic Attorney Docket No.103361-532WO1 turnover. Within this expansive field, the hydrogenation of terminal olefins has emerged as an important reaction in and of itself and therefore has been extensively studied. Motivated by both economic and environmental considerations, there has been a drive to replicate and expand on the reactivity of precious metal catalysts with earth-abundant first-row transition metal complexes as catalysts for olefin hydrogenation. However, there are a variety of challenges associated with this goal, most notably that there have been fewer detailed investigations of the reactivity and mechanisms of first-row transition metal catalysts. Complexes that feature cobalt(I) or cobalt(II) centers supported by pincer ligands have emerged as an important class of olefin hydrogenation catalysts in their own right. In particular, work by Chirik, Hanson, Lu, Jones, Fout, Gade, Tonzetich, Anderson, Huang, and Peters has demonstrated the utility of pincer-ligated cobalt complexes to efficiently catalyze olefin hydrogenation at room temperature with low catalyst loading. Scheme 1. Representative Examples of Cobalt Catalysts for Alkene Hydrogenation and Their Catalytic Activity for the Hydrogenation of Styrene at Room Temperature. Attorney Docket No.103361-532WO1 In prior work, our group reported facile H2 activation by the formally Co(I) complex, (PPP)Co(PMe3); however, attempts to use this complex as a catalyst for olefin hydrogenation were unsuccessful. Instead, we developed a protocol for the in situ activation of a Co(II) complex, (PPClP)CoCl2, with KBEt3H to generate an active catalyst for the room temperature hydroboration of terminal olefins. This catalytic system displayed short reaction times and high selectivity for the anti-Markovnikov hydroboration products. With this catalytic activity demonstrated, we sought to explore olefin hydrogenation reactions using a similar Co(II) precatalyst. Results and Discussion In this Example, we report the synthesis of a pincer-ligated Co(II) complex featuring a central N-heterocyclic phosphine and demonstrate its catalytic activity for the hydrogenation of terminal olefins. Addition of the N-heterocyclic phosphine-containing pincer ligand, PPHP, to CoI2(1.2 equiv) in THF results in the precipitation of a dark yellow solid, (PPHP)CoI2(1) (Scheme 1). Similar to (PPClP)CoCl2, the1H NMR spectrum of CoIIcomplex 1 contains 10 broad paramagnetically shifted resonances. The solid-state structure of 1 confirms the proposed formulation, wherein a CoI2fragment is ligated by the pincer ligand with the P−H bond of the central N-heterocyclic phosphine intact (Figure 1). The coordination geometry of the cobalt center is distorted square pyramidal (τ5 = 0.40). Although the poor solubility of 1 prevented an Evans’ method solution magnetic moment measurement, we posit that 1 adopts an S = 1 / 2 spin state in accordance with the analogous (PPClP)CoCl2compound. Scheme 1. Synthesis of (PPHP)CoI2(1). With 1 in hand, we sought to explore its utility as a precatalyst for the hydrogenation of styrene using KBEt3H as an activator. In the absence of substrates, 1 reacts with KBEt3H to produce the previously reported dimeric species [(PPP)-CoH]2, which was previously shown to be inactive for hydroboration catalysis and is likewise inactive toward styrene hydrogenation (Table 1). Thus, we chose to prevent the formation of [(PPP)CoH]2 by preventing the reaction Attorney Docket No.103361-532WO1 between 1 and KBEt3H prior to the addition of H2. This was accomplished by combining 1 (2 mol %) and styrene in C6D6in a Schlenk tube under a nitrogen atmosphere, freezing the reaction vessel with liquid N2, replacing the headspace with 1 atm of H2, and introducing KBEt3H (4 mol %) to generate the catalytically active species in situ. The reaction mixture was allowed to warm to room temperature and stirred for 90 min; during which time, the color of the solution proceeded from green to a deep red coloration, indicating the formation of the catalytically inactive dimer [(PPP)CoH]2. The reaction mixture was then analyzed by GC-MS and1H NMR spectroscopy, revealing ethylbenzene as the sole organic product. In the1H NMR spectrum, there are resonances at 3.69 and 3.29 ppm and a broad resonance at −8.32 ppm that correspond to the methylene backbone protons of the pincer ligand and the cobalt hydride of [(PPP)CoH]2. The31P{1H} NMR spectrum of the reaction mixture unambiguously confirms that [(PPP)CoH]2is the sole metal-containing product. Next, we sought to further probe and optimize the catalytic alkene hydrogenation conditions using styrene (2a) as a model substrate (Table 1). Although our initial screening involved careful exclusion of air and moisture, it was quickly discovered that catalysis was not significantly impacted by the deliberate addition of small quantities of air or water, with hydrogenation proceeding to completion in the presence of either. The (PPHP)CoI2 / KBEt3H system, therefore, exhibits appreciable stability toward adventitious exposure to atmospheric contamination. Indeed, when the hydrogenation reactions were performed under less rigorous conditions using round-bottom flasks and rubber septa, 1 atm of H2could easily be introduced via balloon with no significant impacts to reaction outcome. Even at very low catalyst loading (0.1−0.5 mol %), it was possible to achieve yields >90% for the reduction of 2a to ethylbenzene with prolonged reaction times. However, as our goal was to develop a catalytic system that demonstrated both ease-of-use and widespread application, we decided on a catalyst loading of 2 mol % for our further studies. It was found that this loading offered higher yields across our examined substrate scope without requiring the use of specialized glassware to establish rigorously air- and moisture-free conditions. Attorney Docket No.103361-532WO1 Table 1. Additional screening conditions for the catalytic hydrogenation of styrene. The molecular / homogeneous nature of the in situ generated hydrogenation catalyst was next probed using a series of control reactions (Table 1). In the absence of either 1 or KBEt3H, no catalytic activity was observed (Table 1). Catalysis was not found to be hindered by the addition of metallic mercury, supporting a homogeneous reaction. More convincingly, we found that catalysis was halted entirely by the addition of PMe3, which is consistent with previous observations that alkene hydroboration is halted by the formation of the catalytically inactive species (PPHP)Co-(H)(PMe3) upon addition of PMe3 to an in-progress hydroboration reaction using the (PPClP)CoCl2 / KBEt3H system. With our optimal catalytic conditions in hand, we sought to explore a wider substrate scope (Scheme 2) to determine the capabilities and limitations of our catalytic system. Variously Attorney Docket No.103361-532WO1 4-substituted styrene derivatives (2b−2f) were screened.4-Methylstyrene (2b, >99%), 4- methoxystyrene (2c, 95%), 4-trifluoromethylstyrene (2d, >99%), and 4-chlorostyrene (2e, 90%) were all readily reduced under standard conditions within 90 min; only 4-bromostyrene (2f, 66%) failed to provide the reduced product in high yields, requiring the reaction to be kept cold to achieve modest conversion, which is most likely a result of the more easily activated C−Br bond of 2f. The terminal alkene of 3,3-dimethylbutene (2g), 3-phenylpropene (2h), and 1-octene (2i) are reduced in high yield to the corresponding alkanes 3,3-dimethylbutane (82%), propylbenzene (97%), and octane (89%), respectively. In the case of substrates that were capable of chain-walking, such as 2h and 2i, a small quantity of the internal olefin products of chain- walking were detected. Attempts to hydrogenate internal olefins such as trans-2-octene (2j) afforded no reduction products, even at elevated hydrogen pressures (ca.3 atm). Interestingly, some substrates, such as allylphenylether (2k) and 5-hexen-2-one (2l) failed to afford the reduction products in satisfactory yield when using C6D6. Using THF-d8as the reaction solvent, however, enabled the conversion of 2k to propylphenylether (92%) and 2l to 2-hexenone (75%) with longer reaction times. Hoping to demonstrate the reduction of a more sterically encumbered 1,1′-alkene, we chose to investigate the hydrogenation of α-methylstyrene (2m). Initially, reduction of 2m resulted in a maximum yield of 37% under our standard protocol in 90 min. Allowing the reaction to proceed for a total of 3 h provided a modest increase in yield (50%). However, increasing the catalyst loading (4 mol % 1, 8 mol % KBEt3H) and stirring for 3 h was found to provide the greatest conversion of 2m (76%). The conversion of 2m to isopropylbenzene was found to be insensitive to solvent (THF / C6D6) or gentle heating (40 °C) over 3 h. The related 1,1′-substituted alkene substrate, limonene (2n), bearing both internal and terminal olefins was noted to react slowly at the terminal olefin, requiring 4 mol % 1 and 12 h of stirring to afford 1-methyl-4-propan-2-ylcyclohexene (90%). Comparing the catalytic activity of the 1 / KBEt3H system to previously reported cobalt catalysts for olefin hydrogenation reveals that the low catalyst loading, mild conditions (1 atm H2, rt), and short reaction times are comparable to the best-known systems (Scheme 1). However, the sluggish activity of 1 / KBEt3H toward 1,2-disubstituted alkenes at room temperature is a notable limitation. It may be possible, however, to devise a more active catalyst for more challenging substrates through modification of the ligand framework and a structure / activity relationship study is therefore underway. Attorney Docket No.103361-532WO1 Scheme 2. Substrate Scope and General Conditions for the Hydrogenation (rt, 1 atm H2) of Variously Substituted Olefins Using 1 (2 mol %) in the Presence of KBEt3H (4 mol%) as an Activator. Conclusion In summary, the CoIIpincer complex (PPHP)CoI2(1) effectively catalyzes the hydrogenation of terminal olefins when activated with KBEt3H. Styrene derivatives and a variety of other terminal olefins are hydrogenated with good to excellent yields at a low catalyst Attorney Docket No.103361-532WO1 loading (2 mol %) and under mild conditions (1 atm H2, rt, 90 min). Under the optimized conditions, the only metal-containing product that was spectroscopically observed at the end of catalysis was the dimeric species [(PPP)CoH]2, strongly implicating a monomeric cobalt hydride-containing species as the active catalyst. Future studies will seek to gain insight into the mechanism of this catalytic hydrogenation reaction and to leverage this hydrogenation reactivity toward a broader range of substrates. Materials and Methods General Considerations. Unless otherwise noted, all manipulations were carried out under an inert atmosphere using a nitrogen-filled glovebox or standard Schlenk techniques. Glassware was oven-dried before use. All proteo solvents were degassed by sparging with ultra- high purity argon and dried via passage through columns of drying agents using a Glass Contours solvent purification system from Pure Process Technologies. Benzene-d6 was degassed via repeated freeze-pump-thaw cycles and dried over 3 Å molecular sieves before use. CD2Cl2 was dried over CaH2, vacuum transferred, and degassed via repeated freeze-pump-thaw cycles. Styrene derivatives were either filtered over basic alumina to remove stabilizers or distilled under vacuum and stored in a glovebox at −35 °C over 3 Å molecular sieves. All alkenes not containing an enolizable functional group were stored over 3 Å molecular sieves before use. KBEt3H was purchased from Sigma-Aldrich as a 1 M solution in THF and used without further purification. (PPClP)CoCl2, PPClP, and PPHP were synthesized according to literature procedures. NMR spectra were recorded at ambient temperature unless otherwise stated on a Bruker DPX 400 MHz or Bruker AVIII 600 MHz instrument.1H NMR chemical shifts were referenced to residual solvent resonances and are reported in ppm.31P NMR chemical shifts (in ppm) were referenced to 85% H3PO4(0 ppm) using an external standard. All other reagents and solvents were obtained from commercial sources and used without further purification. GC-MS analysis was performed using an Agilent 7890B GC system equipped with the HP-5 Ultra Inert column (30 m, 0.25 mm, 0.25 μm), and a FID detector. For MS detection, an electron ionization system was used with an ionization energy of 70 eV. Elemental microanalyses were performed by Midwest Microlab, Indianapolis, IN. Synthesis of (PPHP)CoI2(1). Cobalt(II) iodide (0.377 g, 1.21 mmol) was dissolved in THF (5 mL) in a 100 mL round bottom flask equipped with a stir bar and stirred at room temperature. PPHP (0.614 g, 1.00 mmol) was dissolved in THF (10 mL) then added to the stirring solution of cobalt(II) iodide. The color of the solution immediately became brown. Concurrently, a yellow solid began to precipitate out of solution. The reaction was allowed to stir overnight to ensure completion. The dark yellow solid was then collected on a frit and Attorney Docket No.103361-532WO1 washed with THF (10 mL) and hexanes (30 mL) then triturated with CH2Cl2 to yield 1 as an analytically pure powder (0.634 g, 68%). Crystals of 1 suitable for X-ray diffraction were grown via diffusion of Et2O vapor into a concentrated CH2Cl2solution of 1 at room temperature.1H NMR (600 MHz, CD2Cl2): δ 9.23, 8.97, 8.18 (very broad), 7.59 (very broad), 7.24, 6.46, 5.52, 4.50, 1.27, -1.86 (very broad). Anal. Calcd for C38H33N2P3CoI2: C, 49.43; H, 3.60; N, 3.03. Found: C, 47.70; H, 3.51: N, 2.82.1 is quite sensitive to air and moisture, so the low %C value is attributed, at least partially, to oxidation of the central phosphorus atom during shipping and handling (e.g., C38H33N2OP3CoI2: C, 48.59; H, 3.54; N, 2.98). Reaction between 1 and KBEt3H to afford [(PPP)CoH]2. Compound 1 (0.026 g, 0.028 mmol) was dissolved in THF (5 mL) in a 20 mL scintillation vial equipped with a magnetic stir bar. While stirring this suspension, a solution of KBEt3H (56.1 μL, 0.056 mmol) was added via micropipette. The color of the mixture immediately became dark red, and the solution became homogeneous. The reaction was allowed to stir for 30 min, then the volatile components were removed in vacuo. The remaining dark red residue was extracted into benzene and the solution was filtered through a Celite plug in a pipette with a piece of glass microfiber filter paper. The remaining volatile components were then removed from the filtrate in vacuo. The resulting powder was then extracted into diethyl ether and any insoluble material was removed by filtration through a Celite plug in a pipette with a piece of glass microfiber filter paper. The volatile components were removed from the filtrate in vacuo, after which the resulting dark red solid was triturated with benzene to yield [(PPP)CoH]2(0.012 g, 62%). The identity of [(PPP)CoH]2 was confirmed by comparison to previously reported1H and31P NMR data. Hydrogenation Procedures Hydrogenation of styrene (2a). To an oven-dried 5 mL round bottom flask was added 1 (6.9 μmol, 5.1 mg, 2.0 mol %), styrene (346 μmol, 36.0 mg), and benzene-d6(1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -78°C and the headspace evacuated and purged with H2 three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 14 μL, 4 mol %) was added and the reaction mixture allowed to warm to room temperature. The reaction was stirred for 90 minutes. Hexamethylbenzene (175 μmol, 28.4 mg, 0.5 equiv) was added as an internal standard and the Attorney Docket No.103361-532WO1 mixture was filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of ethyl benzene, which was quantified by1H NMR spectroscopy by comparison of hexamethylbenzene (s, 2.14 ppm, 18H) to the resonance of the benzylic position of ethylbenzene (NMR yield: 99%). NMR (400 MHz, C6D6): δ 7.18 - 7.15 (m, 2H), 7.09 – 7.04 (m, 3H), 2.44 (q, J = 7.6 Hz, 2H), 1.08 (t, J = 7.7 Hz, 3H). Hydrogenation of 4-methylstyrene (2b). To an oven-dried 5 mL round bottom flask was added 1 (8.8 μmol, 8.1 mg, 2.0 mol %), 4-methylstyrene (442 μmol, 52.2 mg), and benzene- d6 (1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace evacuated and purged with H2three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 18 μL, 4 mol %) was added and the reaction mixture allowed to warm to room temperature. The reaction was stirred for 90 minutes. Hexamethylbenzene (221 μmol, 35.8 mg, 0.5 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of 4-ethyltoluene, which was quantified by1H NMR spectroscopy by comparison of hexamethylbenzene (s, 2.14 ppm, 18H) to the triplet resonance of the benzylic position of 4-ethyltoluene (NMR yield: >99%).1H NMR (400 MHz, C6D6) δ 6.98 (s, 4H), 2.45 (q, J = 7.6, 2H), 2.14 (s, 3H), 1.09 (t, J = 7.6, 3H). Hydrogenation of 4-vinylanisole (2c). To an oven-dried 5 mL round bottom flask was added 1 (3.0 μmol, 5.6 mg, 2.0 mol %), 4-vinylanisole (320 μmol, 43.0 mg), and benzene-d6 (1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -78°C and the headspace evacuated and purged with H2three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 12 μL, 4 mol %) was added and the reaction mixture allowed to warm to room temperature. The reaction was stirred for 90 minutes. Hexamethylbenzene (137 μmol, 22.2 mg, 0.43 equiv) was added as an internal standard Attorney Docket No.103361-532WO1 and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of 1-ethyl-4-methoxybenzene, which was quantified by1H NMR spectroscopy by comparison of hexamethylbenzene (s, 2.14 ppm, 18H) to the aromatic resonances of 1-ethyl-4-methoxybenzene (NMR yield: 95%).1H NMR (400 MHz, C6D6) δ 7.13 (d, J = 8.7, 2H), 6.80 (d, J = 8.7, 2H), 3.35 (s, 3H), 2.45 (q, J = 7.6, 2H), 1.11 (t, J = 7.6, 3H). Hydrogenation of 4-trifluoromethylstyrene (2d). To an oven-dried 5 mL round bottom flask was added 1 (2.7 μmol, 2.0 mg, 2.0 mol %), 4-trifluoromethylstyrene (112 μmol, 19.2 mg), and benzene-d6 (1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -78°C and the headspace evacuated and purged with H2three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 5.4 μL, 4 mol %) was added and the reaction mixture allowed to warm to room temperature. The reaction was stirred for 3 hours. Hexamethylbenzene (64 μmol, 10.4 mg, 0.57 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of 1-ethyl-4-trifluoromethylbenzene, which was quantified by1H NMR spectroscopy by comparison of hexamethylbenzene (s, 2.14 ppm, 18H) to the quartet resonance of the benzylic position of 1-ethyl-4-trifluoromethylbenzene (NMR yield: >99%).1H NMR (600 MHz, C6D6) δ 7.32 (d, J = 7.8 Hz, 2H), 6.77 (d, J = 7.8 Hz, 2H), 2.21 (q, J = 7.6 Hz, 2H), 0.91 (t, J = 8.2 Hz, 3H). Hydrogenation of 4-chlorostyrene (2e). To an oven-dried 5 mL round bottom flask was added 1 (3.1 μmol, 2.9 mg, 2.0 mol %), 4-chlorostyrene (157 μmol, 21.8 mg), and benzene-d6(1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace evacuated and purged with H2three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 6.4 μL, 4 mol %) was added and the reaction mixture allowed to warm to room temperature. The reaction was stirred Attorney Docket No.103361-532WO1 for 90 minutes. Hexamethylbenzene (39 μmol, 6.4 mg, 0.25 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of 1-chloro-4-ethylbenzene, which was quantified by1H NMR spectroscopy by comparison of hexamethylbenzene (s, 2.14 ppm, 18H) to the resonance of the benzylic position of 1-chloro-4-ethylbenzene (NMR yield: 90%).1H NMR (600 MHz, C6D6) δ 7.11 (d, J = 7.6, 2H), 6.70 (d, J = 7.6, 2H), 2.23 (q, J = 7.5, 2H), 0.94 (t, J = 7.6 Hz, 3H). Hydrogenation of 4-bromostyrene (2f). To an oven-dried 5 mL round bottom flask was added 1 (9.56 μmol, 7.0 mg, 2.5 mol %), 4-bromostyrene (382 μmol, 70 mg), and benzene-d6 (1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace evacuated and purged with H2three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 6.8 μL, 4 mol %) was added and the reaction mixture warmed to 5 oC in a chilled water bath. The reaction was stirred for 90 minutes and allowed to warm to room temperature over the reaction period. Hexamethylbenzene (78.4 μmol, 12.7 mg, 0.21 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of 1-bromo-4-ethylbenzene,8 which was quantified by 1H NMR spectroscopy by comparison of hexamethylbenzene (s, 2.14 ppm, 18H) to the resonance of the benzylic position of 1-bromo-4-ethylbenzene (NMR yield: 66%).1H NMR (600 MHz, C6D6) δ 7.26 – 7.23 (m, 2H), 7.20 – 7.18 (m, 2H), 2.21 (q, J = 7.6, 2H), 0.93 (t, J = 7.5 Hz, 3H). Hydrogenation of 3,3-dimethyl-1-butene (2g). To an oven-dried 5 mL round bottom flask was added 1 (4.7 μmol, 3.5 mg, 2.0 mol %), 3,3-dimethylbut-1-ene (234 μmol, 19.7 mg), and benzene-d6 (1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace evacuated and purged with H2 three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 10 μL, 4 mol Attorney Docket No.103361-532WO1 %) was added and the reaction mixture was allowed to warm to room temperature. The reaction was stirred for 90 minutes. Hexamethylbenzene (154 μmol, 25.1 mg, 0.66 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of 2,2-dimethylbutane,10 which was quantified by 1H NMR spectroscopy by comparison of hexamethylbenzene (s, 2.14 ppm, 18H) to the singlet resonance of 2,2-dimethylbutane (NMR yield: 82%).1H NMR (400 MHz, C6D6) δ 1.17 (q, J = 7.2, 2H), 0.84 (s, 9H), 0.80 (t, J = 7.5, 3H). Hydrogenation of allyl benzene (2h). To an oven-dried 5 mL round bottom flask was added 1 (3.3 μmol, 3.0 mg, 2.0 mol %), allyl benzene (151 μmol, 17.9 mg), and benzene-d6 (1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace evacuated and purged with H2 three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 7 μL, 4 mol %) was added and the reaction mixture allowed to warm to room temperature. The reaction was stirred for 90 minutes. Hexamethylbenzene (81.3 μmol, 13.2 mg, 0.54 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of n-propylbenzene, which was quantified by1H NMR spectroscopy by comparison of hexamethylbenzene (s, 2.14 ppm, 18H) to the resonance of the benzylic position of n-propylbenzene (NMR yield: 97% n-propylbenzene / 2% trans-β-methylstyrene).1H NMR (400 MHz, C6D6) δ 7.18-7.14 (m, 2H), 7.08-7.02 (m, 3H), 2.41 (t, J = 7.4, 2H), 1.50 (sextet, J = 7.4, 2H), 0.81 (t, J = 7.4, 3H). Hydrogenation of 1-Octene (2i). To an oven-dried 5 mL round bottom flask was added 1 (5.1 μmol, 4.7 mg, 2.0 mol %), 1-octene (254 μmol, 28.6 mg), and benzene-d6(1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace was evacuated and purged with H2 three times using a double- walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 10.0 μL, 4 mol %) was added and the reaction mixture was allowed to warm to room temperature. The reaction was stirred for 90 minutes. Hexamethylbenzene (63.7 μmol, 10.3 mg, 0.25 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of octane, which was quantified by1H Attorney Docket No.103361-532WO1 NMR spectroscopy by comparison of hexamethylbenzene (s, 2.14 ppm, 18H) to the methyl resonance of octane (NMR yield: 89%).1H NMR (600 MHz, C6D6) δ 1.28 (m, 12H), 0.90 (t, J = 7.5 Hz, 6H). Attempted hydrogenation of trans-2-octene (2j). To an oven-dried 5 mL round bottom flask was added 1 (5.1 μmol, 4.7 mg, 3.0 mol %), trans-2-octene (240 μmol, 27.0 mg), and benzene-d6(1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace was evacuated and purged with H2 three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 10.0 μL, 4 mol %) was added and the reaction mixture was allowed to warm to room temperature. The reaction was stirred for 90 minutes before being filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with the starting material 2n. Hydrogenation of allyl phenyl ether (2k). To an oven-dried 5 mL round bottom flask was added 1 (15 μmol, 10.1 mg, 5.0 mol %), allyl phenyl ether (292 μmol, 39.1 mg), and THF- d8(1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace evacuated and purged with H2 three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 30 μL, 10 mol %) was added and the reaction mixture allowed to warm to room temperature. The reaction was stirred for 12 hours. Trimethoxybenzene (140 μmol, 23.6 mg, 0.48 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of phenyl propyl ether, which was quantified by1H NMR spectroscopy by comparison of trimethoxybenzene (6.23 ppm, 3H and 3.30 ppm, 9H) to the average integrations of the resonances of phenyl propyl ether at 1.57 and 0.84 ppm (NMR yield: 92%).1H NMR (600 MHz, C6D6) δ 7.14 – 7.12 (m, 2H), 6.85 – 6.83 (m, 2H), 3.56 (t, 2H), 1.57 (q, J = 7.2, 2H), 0.84 (t, J = 7.4 Hz, 3H). Attorney Docket No.103361-532WO1 Hydrogenation of 5-hexen-2-one (2l). To an oven-dried 5 mL round bottom flask was added 1 (6.0 μmol, 5.2 mg, 2.0 mol %), 5-hexen-2-one (306 μmol, 30.0 mg), and THF-d8(0.6 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace was evacuated and purged with H2 three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 14 μL, 4 mol %) was added and the reaction mixture was allowed to warm to room temperature. The reaction was stirred for 6 hours. Trimethoxybenzene (38.7 μmol, 6.5 mg, 0.12 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of 2-hexanone, which was quantified by1H NMR spectroscopy by comparison of trimethoxybenzene (6.23 ppm, 3H and 3.30 ppm, 9H) to the triplet resonance (1.96 ppm) of 2-hexanone (NMR yield: 75%).1H NMR (400 MHz, C6D6) δ (t, J = 7.3, 2H), 1.69 (s, 3H), 1.40 (m, 2H), 1.11 (m, 2H), 0.77 (t, J = 7.4, 3H). Hydrogenation of α-methylstyrene (2m). To an oven-dried 5 mL round bottom flask was added 1 (12 μmol, 11 mg, 4.0 mol %), α-methylstyrene (301 μmol, 35.6 mg), and benzene- d6 (1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace evacuated and purged with H2 three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 25 μL, 8 mol %) was added and the reaction mixture allowed to warm to room temperature. The reaction was stirred for 3 hours. Trimethoxybenzene (83.8 μmol, 14.1 mg, 0.28 equiv) was added as an internal standard and the mixture filtered through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of isopropylbenzene, which was quantified by1H NMR spectroscopy by comparison of trimethoxybenzene (6.23 ppm, 3H and 3.30 ppm, 9H) to the multiplet resonance of the benzylic position of isopropylbenzene (NMR yield: 76%).1H NMR (400 MHz, C6D6) δ 7.18 – 7.14 (m, 2H), 7.09 – 7.03 (m, 3H), 2.68 (hept, J = 6.8, 1H), 1.11 (d, J = 7.0, 6H). Attorney Docket No.103361-532WO1 Hydrogenation of limonene (2n). To an oven-dried 5 mL round bottom flask was added 1 (4.6 μmol, 3.4 mg, 2.0 mol %), (S)-(-)-limonene (228 μmol, 31.0 mg), and benzene-d6 (1 mL) before being sealed under a septum and removed from the glovebox. The reaction mixture was cooled to -196°C and the headspace was evacuated and purged with H2 three times using a double-walled balloon. Using a glass syringe, KBEt3H (1 M in THF, 10 μL, 4 mol %) was added, the balloon removed, and the reaction mixture was allowed to warm to room temperature with stirring for 12 hours. Trimethoxybenzene (42 umol, 7.1 mg, 0.19 equiv) was added prior to filtration through glass microfiber filter paper. Analysis of the filtered reaction mixture was consistent with literature reports of 1-methyl-4-(propan-2-yl)cyclohex-1-ene, which was quantified by1H NMR spectroscopy by comparison of trimethoxybenzene (6.23 ppm, 3H and 3.30 ppm, 9H) to the internal olefin resonance of rac-1-methyl-4-(propan-2-yl)cyclohex-1-ene (NMR yield: 90%).1H NMR (400 MHz, C6D6) δ 5.44 - 5.42 (m, 1H), 1.96 – 1.88 (m, 2H), 3.57 (s, 3H), 2.45 (s, 2H), 1.11 (s, 3H). Alkene Hydrogenation in the presence of PMe3. To an oven-dried 5 mL round bottom flask was added 1 (3.3 μmol, 3.0 mg, 2.0 mol %), styrene substrate (162.5 μmol, 19.2 mg), and benzene-d6(1 mL) before being sealed under inert atmosphere and removed from the glovebox. An aliquot was taken for NMR analysis and the reaction mixture was cooled to -196°C and the headspace was evacuated and purged with H2 three times using a double-walled balloon. Using a glass syringe, KBEt3H, (1 M in THF, 6.5 μmol, 4 mol %) was added, the cooling bath removed, and this mixture was allowed to stir for approximately 15 minutes before an aliquot was taken to confirm catalytic activity. After 5 additional minutes, trimethylphosphine (3.3 μmol, 3.4 μL, 2 mol %) was added. The reaction mixture was allowed to stir for an additional 60 minutes before taking a final aliquot to determine starting material consumption. Analysis of the reaction mixture after 90 minutes confirmed inhibition of catalytic activity after addition of trimethylphosphine. Procedure for Attempted Styrene Hydrogenation Catalysis with [(PPP)CoH]2. To an oven-dried 5 mL round bottom flask was added [(PPP)CoH]2 (13.6 μmol, 10.0 mg, 2.0 mol %), styrene (162.5 μmol, 67.7 mg), and benzene-d6 (1 mL) before being sealed under inert Attorney Docket No.103361-532WO1 atmosphere and removed from the glovebox. The reactor headspace was evacuated and purged with H2three times using a double-walled. This mixture was allowed to stir for 12 hours at room temperature before the reaction mixture was filtered through glass microfiber filter paper. Analysis of the resultant solution by1H NMR was consistent with starting material and trace ethylbenzene, confirming that the dimeric [(PPP)CoH]2 is not catalytically competent for the hydrogenation of styrene, even with extended reaction times. X-ray Crystallography. The single crystal X-ray diffraction studies were carried out on a Bruker D8 Venture Kappa diffractometer equipped with Mo (TXS-HB) Kɑ radiation (λ = 0.71073 Å) and a Photon III CPAD detector. The crystal of 1, grown by diffusion of Et2O vapor into a concentrated CH2Cl2solution, was mounted on a MiTeGen Micromount with Paratone 24EX oil. Data were collected in a nitrogen gas stream at 100(2) K using ɸ and ω scans. Data collection was 99.9% complete to 25.00° in θ (0.83Å). The crystal-to-detector distance was 50 mm using variable exposure time (2s to 20s) depending on θ with a scan width of 1.0°. A total of 92348 reflections were collected with indices –46 ≤ h ≤ 46, –12 ≤ k ≤ 12, –29 ≤ l ≤ 29. Of these, 7335 reflections were found to be symmetry independent, with a Rint of 0.0656. Indexing and unit cell refinement indicated a c-centered monoclinic lattice with space group C2 / c. The data were integrated using the Bruker SAINT13 software program and scaled using the SADABS14 software program. Structure solution and refinement were done within the Olex2 software package. Solution by direct methods (SHELXT16) produced a complete phasing model for refinement. All nonhydrogen atoms were refined anisotropically by full-matrix least-squares (SHELXL-201417). All carbon-bonded hydrogen atoms were placed using a riding model with positions constrained relative to their parent atom using the appropriate HFIX command in SHELXL-2014. The phosphorus-bonded hydrogen on 1 was located in the difference map, and its relative position and thermal parameter were freely refined. Example 2. Evaluation of Additional Catalytic Complexes. Using similar synthetic strategies, additional catalytic complexes (including 2, 2b, 3, 3b, 4, and 5 shown below) were prepared and evaluated. Synthetic strategies for preparing these complexes are shown in Figure 3 and Figure 4. Attorney Docket No.103361-532WO1 These catalysts, in particular complex 3 and complex 4, were shown to have excellent activity as hydrogenation catalysts. These catalysts were also evaluated as hydroboration catalysts, with all displaying activity. Substitution of the central phosphorous atom was shown to impact catalytic activity, with more electron withdrawing substituents resulting in increased activity. Attorney Docket No.103361-532WO1 Central phosphorous substitution leads to 200-fold increase in catalytic activity These catalysts showed activity with a range of substrates, as shown below. Recharge experiments were also performed as shown below. Example 3. Synthesis and Assessment of a Highly Active Alkene Hydroboration Catalyst via an Air-Stable PPCF3PCoI2Pre-Catalyst Summary A previously characterized Co(II) complex (PPHP)CoI2, was shown by exhibit modest activity (TON = 50) towards the hydrogenation of terminal alkenes under mild conditions (1 atm H2, 25 °C) when activated by two equivalents of KBEt3H. The (PPHP)CoI2 / KBEt3H system was Attorney Docket No.103361-532WO1 primarily found to be limited by a rapid dimerization process that yields the catalytically inactive species [PPPCoH]2. This dimer formation was found to be irreversible and reacted further under vacuum to formally lose H2, generating [PPPCo]2. Seeking to probe the catalytic mechanism and prevent dimerization of the active species (a purported Co-H), we envisioned that the installation of a trifluoromethyl- group on the central phosphorous would afford increased stability (vide infra) to the resultant cobalt complex, while also providing a highly sensitive NMR handle using19F NMR. In this example, we report the synthesis of a new Co(II) pre-catalyst, (PPCF3P)CoI2 , which was found to function as an alkene hydrofunctionalization catalyst with significantly increased activity when compared to (PPClP)CoCl2with a 200-fold increase in catalytic activity (TON = 10,000) for the hydroboration of styrene. Functional-group tolerances were probed through a substrate scope of electronically and sterically distinct alkenes. A mechanism is proposed based on catalytic, stoichiometric, and substrate competition experiments using styrene derivatives. In the absence of the hydroborating reagent, pinacol borane (HBpin), activation of the Co(II) pre-catalyst in the presence of styrene affords a single species, (PPCF3P)Co(η2- styrene)H which has been isolated, characterized, and demonstrated as an active catalyst for hydroboration in the absence of additional activators. Introduction Organoboranes have been established as privileged synthons due to the wide range of transformations that they can undergo, including the Brown Hydroboration-Oxidation sequence and as cross-coupling reagents for carbon-carbon bond formation such as the Suzuki-Miyaura coupling. The versatility of organoborane reagents in the synthesis of complex molecules necessitates a diverse chemical “toolkit” capable of accessing large libraries of organoboranes. The hydroboration of alkenes, catalyzed by transition-metal (TM) complexes (often with noble metals) is known to afford high atom-economy and selectivity. It has only been in recent decades, however, that significant attention has been paid to the more abundant first-row transition metals like cobalt or iron, in part due to concerns regarding the long-term usage of noble metals, which are relatively more scarce, and often more toxic than first-row TMs. In the case of first-row TMs, pincer ligands have become ubiquitous as a means to tune the reactivity of the metal-center towards the substrate of interest, while imparting high thermal stability and steric-bulk to discourage undesirable side-reactivity. A small selection of recent literature examples of pincer-ligated cobalt complexes and their styrene hydroboration activity is provided in Figure 5. A CoIIcomplex reported by the Roşca group in 2023 provided for the conversion of styrene under mild conditions to the anti-Markovnikov product using a redox- active pyrimidinediimine ligand (PPymDipp). In 2017, Thomas reported a bipyridyl-oxazoline Attorney Docket No.103361-532WO1 supported cobalt dichloride complex that when activated by sodium tert-butoxide, afforded excellent selectivity for the branched regioisomer. Around the same time, the Fout group reported the hydroboration activity of an N-heterocyclic carbene derived CoIdinitrogen complex with rapid conversion of terminal alkenes. In 2013, Chirik reported a pyridine diimine based CoIalkyl precatalyst ((MesPDI)CoCH3) that gave full conversion of terminal alkenes in 15 minutes; of particular note with the Chirik system is that sterically hindered internalalkenes, both endocyclic and linear, are functionalized under mild conditions (1 mol%, 50 °C, 16 h) via an isomerization-hydroboration sequence. A PCP CoIIchloride from Huang proved to be capable of converting styrene to the linear hydroboration product with part-per-million concentrations of cobalt for sterically un-encumbered alkenes. The conversion of sterically encumbered alkenes (1-5 mol%, 80 – 120 °C, 24 h) was found to proceed through chain-walking to a terminal alkene that is released in a final hydroboration step. We have demonstrated that (PPHP)CoI2and (PPClP)CoCl2are effective pre-catalysts for the hydrogenation and hydroboration of terminal alkenes, respectively. These transformations were found to proceed under mild conditions at room temperature upon activation of the cobalt complex with two equivalents of potassium triethylborohydride. Seeking to develop these protocols and further expand the scope of possible transformations beyond terminal alkenes, we began exploring ligand modifications which could tune the electronic and steric environment of the active catalyst. Ultimately, a trifluoromethyl-derived PPP ligand was found to not only retain the previously observed catalytic activity, but enabled the conversion of internal alkenes, and greatly enhanced reactivity with terminal alkenes (0.01 mol%, 25 °C). Results and Discussion The synthesis of the pincer ligand, PPCF3P, was achieved by nucleophilic trifluoromethylation of the ligand precursor, PPClP, using (trifluoromethyl)trimethylsilane (TMS-CF3) in the presence of KF and 18-crown-6. We note that the trifluoromethyl-phosphine ligand synthesis is particularly sensitive to the purity of the reagents (SI); similar observations have been reported in the literature for nucleophilic trifluoromethylation of carbonyl- compounds. The addition of PPCF3P to a stirring solution of CoI2(1.1 equiv) in THF affords PPCF3PCoI2 (1) in 86.5% yield as a golden-brown solid with modest solubility in polar organic solvents.1H NMR of 1 contains 8 broad resonances in accordance with a paramagnetic Co(II) complex; the pre-catalyst exhibits no discernable19F or31P resonances. Single crystals of 1 were grown by slow evaporation of a concentrated DCM solution at room temperature. The solid-state structure of 1 (Figure 6) confirms that the ligand is bound to a CoI2 fragment with the Attorney Docket No.103361-532WO1 phosphines in a co-planar confirmation with a nearly ideal square pyramidal geometry at cobalt (τ5 =0.04). Magnetic susceptibility of 1 was determined by solution-state Evans’ method (S = 1 / 2). Initially, we found that with respect to styrene, pre-catalyst loading of 1 mol% in the presence of HBpin (1.1 equiv) afforded rapid and complete conversion (Figure 7, Entry 1) of the starting material to the linear, anti-Markovnikov product with a small amount of the hydrogenation product, ethylbenzene detected by GC-MS analysis of the crude reaction mixture. It is notable that catalysis was not found to be impacted by the presence of inhibitors (butylated hydroxytoluene), and these were not removed during our condition optimizations. Reducing the catalyst loading to 0.5 mol% (Entry 2 – 4) showed excellent conversion and only trace styrene was detected in 12 minutes when the reaction was warmed to 50 °C (Entry 4). The catalytic loading could be further reduced to 0.1 mol% (Entry 5, 6) without significant impact to catalytic outcomes when reactions were run at room temperature. Reactions run with a precatalysts loading of 0.01% were sluggish (Entry 9) at room temperature (>24 h), but high conversion to the linear hydroboration product was still observed when the quenched reaction mixture was analyzed after approximately 48 hours; heating was found to provide significant enhancement to the rate of reaction (Entry 10), affording >99% conversion of the starting material after 13 hours. Hoping to establish mild conditions across a wide range of substrates, we ultimately chose to proceed with a general loading of 0.1 mol% in precatalyst. As shown in Table 2, we evaluated the reactivity of 1 with a variety of monosubstituted alkene substrates. Electronically differentiated styrenes bearing electron withdrawing groups such as 4-bromostyrene (Entry 2), 4-chlorostyrene (Entry 3), and 4-fluorostyrene (Entry 4) furnished the linear hydroboration product in 87.7% (isol.), 85% (isol.), and 92.5% (NMR) yields respectively. Conversion of 4-trifluoromethylstyrene (Entry 5) was found to proceed slowly at room temperature, affording a 74.0% yield of the anti-Markovnikov product (NMR) after 24 hours. The sluggish reactivity of 4-trifluoromethylstyrene is likely resultant from the significant electron-withdrawing effects from the trifluoromethyl- group; furthermore, the stark reactivity difference between trifluoro- and fluorostyrene suggest that the π-donating character of the fluorine atom of 4-fluorostyrene may play a role, whereas trifluoromethyl substituents are implicated as the stronger σ-withdrawing group.4-Nitrostyrene (Entry 6) was not well tolerated by this system and afforded only mixtures of starting material and unidentified organic products. We hypothesize that the incompatibility is a function of undesired reactivity between the metal complex and the pendant nitro- group, rather than the electronic character of the alkene alone, due to apparent catalyst decomposition observed by19F NMR. Attorney Docket No.103361-532WO1 Table 2. Evaluation of monosubstituted alkene substrate scope. All reactions were run at room temperature (24 °C ± 2 °C). Yields given are isolated unless otherwise specified.aReflects unoptimized reaction conditions.bYield determined by NMR using internal standard.c7% hydrogenation product was detected. entry substrate [Co] (mol%) solvent time yield (%) Attorney Docket No.103361-532WO1 Styrene derivatives with electron donating groups, 3-methylstyrene (Entry 10), 4- methylstyrene (Entry 7), and 4-vinylanisole (Entry 9) were converted with an 85.0% (isol.), 96.3% (isol.), and 95.5 % (NMR). Conversion of 4-acetoxystyrene (Entry 11) was initially met with difficulty due to undesired reactivity with KBEt3H. The hydride source was found to cleave the phenoxy-ester moiety, and ultimately led to apparent inhibition of the catalyst as evidenced by the presence of significant starting material. The results of additive tolerance experiments with EtOAc and styrene suggested that the activated complex was not the source of the observed substrate degradation. In the case of ethyl acetate, undesired reactivity was only noted when present during activation of the precatalyst with KBEt3H; when added during catalysis, full conversion of styrene was observed, and analysis of crude mixtures contained no trace of ester degradation. Therefore, we tested the use of potassium tert-butoxide as a milder activator for the pre-catalyst and indeed, the formation of phenol-containing products was significantly reduced. A distribution of products was obtained which indicated that the ester was still labile under these conditions (presence of phenolic organoboranes). As the reactivity of borohydrides and alkoxides with HBpin is well documented, we attribute some of the side-product formation with the generation of more reactive boranes, such as BH3. Dodecene, allyl trimethylsilane, 1,5-hexadiene, triallylamine, and 3-phenylpropene (Entries 12-16) were functionalized in excellent yields. Remarkably, 3-Phenylpropene (Entry 16) was observed to furnish the anti-Markovnikov product in 93.2% yield (isol.) in 1 hour under standard conditions and equivalent catalyst loadings to other substrates tested. Allyl phenyl ether (Entry 17), however, was observed to convert much more slowly than other substrates under similar reagent concentrations. Additionally, we observed diminished hydroboration of allyl phenyl ether when benzene was included as a solvent – a similar finding to the previously reported (PPHP)CoI2 / KBEt3H alkene hydrogenation system. In the case of 5-hexene-2-one, both the ketone and the alkene were completely functionalized when two or greater equivalents of HBpin was used. Reactions with a single equivalent of HBpin, starting from the in-situ generated a product. As shown in Table 3, we also evaluated the reactivity of 1 with a variety of di-substituted alkene substrates. Di-substituted alkenes were found to be well tolerated with these more sterically hindered substrates exhibiting slower conversion times, but increased catalyst loading, or mild heating often gave satisfactory results. In the case of α-methylstyrene and trans-ß- methylstyrene (Entry 1 and Entry 2), the desired linear product was obtained (at 93.9% yield in the case of α-methylstyrene). Limonene (Entry 3) was found to afford thedesired product, but reactions with this substrate were markedly slow under equivalent loadings to α-methylstyrene. Attorney Docket No.103361-532WO1 Trans-2-octene (Entry 4) represented a previously inaccessible substrate for cobalt PPP complexes previously prepared by our laboratory – using (PPCF3P)CoI2, trans-2-octene was successfully hydroborated with gentle heating (30 °C, 0.1 mol%). Trans-4-octene was found to afford a mixture of primarily starting material with small amounts of isomerized products observed by GCMS. Attempts to obtain satisfactory yields through increased catalytic loading (10 mol%), or through heating were unsuccessful. These results suggest that trans-4-octene can reversibly bind with the activated cobalt-hydride species, but that isomerization is too slow to build up significant concentrations of the terminal isomer. A small series of additives were screened to test the robustness of the activated metal complex in the presence of common functional groups. The conversion of styrene (0.5 mol% 1) to the desired product, 4,4,5,5-tetramethyl-2-phenethyl-1,3,2-dioxaborolane, proceeded unhindered in the presence of acetonitrile (20 mol%) or N,N-dimethylacetamide (20 mol%).When ethyl acetate (20 mol%) was used as an additive, it was found that it reacted rapidly with the activator leading to the recovery of pre-catalyst upon filtration. Despite this incompatibility, base-mediated activation of the pre-catalyst led to full turnover. The addition of air (1 mL) or water (1.5 mol%), post-activation, was not found to inhibit catalysis and isolated yields greater than 80% could be obtained after short silica plug. Hydroboration reactions run with 20 mol% isopropylamine or diethylamine were found to proceed to completion, though reduced isolated yields were obtained (68.9 and 70.4% respectively). During our optimizations, we discovered that the activated complex, a purported Co (I) hydride, affords a single observable resonance by19F (d, -63.24 ppm) during the hydroboration of styrene. The observed resonance was present during NMR experiments (1 equiv styrene, 1.1 equiv HBpin) until low styrene concentrations; at which point, a new resonance (c. -65.2 ppm) rapidly grows, with concomitant decreasing of the signal (-63.24 ppm) present during catalysis. Recharge experiments, whereby styrene was added after the total consumption of the peak at - 63.24 ppm, and to our delight, the observed species at -63.24 ppm (19F) was regenerated and the remaining portion of HBpin consumed. This regeneration of the active species was found to proceed nearly completely, but with some degree of degradation apparent from the appearance of small peaks in the fluorine NMR. Through a small change in reagent loading (0.95 equiv HBpin), however – it was found that the activated metal complex was long-lived and converted styrene over 7 recharges to the linear hydroboration product, reflecting a final catalyst loading of c.0.01 mol%. Attempts to isolate catalytically relevant metal species had been previously met with failure due to the instability of the activated species towards oxidation and dimerization to Attorney Docket No.103361-532WO1 [PPPCoH]2 – which significantly limited the value of stoichiometric controls for the purpose of speciating the activated metal complex. Table 3. Evaluation of di-substituted alkene substrate scope. entry substrate solvent time Activation of (PPCF3P)CoI2in the presence of styrene without HBpin did not result in formation of a dimeric cobalt as with related systems reported previously, but instead afforded a single, bright-yellow complex that was determined to correspond to the cobalt monohydride species (PPCF3P)Co(styrene)H ([Co]-2). The19F NMR spectra of [Co]-2 is characterized by a single resonance (d,-63.24 ppm), while the1H{31P} spectrum in combination with correlation experiments (COSY) allowed us to assign the benzylic and distal protons of the bound styrene molecule which experience a significant up-field shift. Complex [Co]-2 enjoys significantly increased solubility in non-polar organic solvents and XRD quality crystals were grown from a concentrated n-pentane solution (-35 °C) over several weeks. The solid-state structure of 2 support our findings based on the NMR spectra, which adopts an η2binding mode rather than spontaneous insertion to generate a cobalt-alkyl. While several attempts were made to verify the composition of [Co]-2 by elemental analysis, no satisfactory results were obtained. We attribute this to the relatively fragile nature of the alkene-adduct, which degrades in the solid / solution- state when exposed to excess moisture. Gratifyingly, when spectroscopically pure [Co]-2 was Attorney Docket No.103361-532WO1 loaded in catalytic quantity with respect to styrene and HBpin – conversion to hydroborated products was observed with complete selectivity for the linear product. A proposed hydroboration mechanism is illustrated in Figure 8. If 2,1-insertion is operative, it is apparent from the lack of detectable branched product that the resultant intermediate is not competent for product formation. Competition kinetics experiments were performed with variously 4-substituted styrene derivatives. When two equivalents of substrate are mixed with one equivalent of HBpin, the alkene with a relatively more electron deficient phenyl ring are preferentially functionalized over the more electron rich substrate. In the case of 4-chlorostyrene and styrene, the product distribution was observed to be slightly greater than 2:1 in favor of 4-chlorostyrene; this is possibly due to a decreased energetic barrier for the product- forming insertion event; the 4-chlorostyrene being a less oxidizing ligand by comparison to the more electron-rich styrene. Competition experiments between 4-fluorostyrene and styrene showed a product distribution that again favored the electron-deficient substrate, however – the ratio was approximately 5:3. Similarly to the unexpected, rapid functionalization of 4- fluorostyrene under single-substrate conditions – the reason for this reduction in product ratio is unclear. When styrene was tested with 4-vinylanisole, analysis of the remaining starting material indicated that styrene consumption was favored by about 1.7:1 (SI table entry). Experiments with 4-chlorostyrene and 4-methylstyrene afford a product ratio of greater than 3:1, again, in favor of the electron-deficient substrate. Investigations are currently underway to further elucidate the catalytic mechanism of hydroborations using the (PPCF3P)CoI2system, and to expand the manifold of reactivity to encompass the broader scope of hydrofunctionalization chemistry (hydrogenation, hydrosilylation). Through the scope of this study, we have demonstrated that (PPCF3P)CoI2represents one of the most active first-row metal hydroboration catalysts with high reactivity across the tested scope at mild temperatures. Attorney Docket No.103361-532WO1 Materials and Methods General Considerations. Unless otherwise noted, all manipulations were carried out under an inert atmosphere using a nitrogen-filled glovebox or standard Schlenk techniques. Glassware was oven-dried before use. All proteo solvents were degassed by sparging with ultra- high purity argon and dried via passage through columns of drying agents using a Glass Contours solvent purification system from Pure Process Technologies. Benzene-d6was degassed via repeated freeze-pump-thaw cycles and dried over 3 Å molecular sieves before use. CD2Cl2 was dried over CaH2, vacuum transferred, and degassed via repeated freeze-pump-thaw cycles. Styrene derivatives were either filtered over basic alumina to remove stabilizers or distilled under vacuum and stored in a glovebox at −35 °C over 3 Å molecular sieves. All alkenes not containing an enolizable functional group were stored over 3 Å molecular sieves before use. KBEt3H was purchased from Sigma-Aldrich as a 1 M solution in THF and used without further purification. (PPClP)CoCl2, PPClP, PPHP were synthesized according to literature procedures.1–3NMR spectra were recorded at ambient temperature unless otherwise stated on a Bruker DPX 400 MHz or Bruker AVIII 600 MHz instrument.1H NMR chemical shifts were referenced to residual solvent resonances and are reported in ppm.31P and19F NMR chemical shifts (in ppm) were referenced to 85% H3PO4 (0 ppm) and neat C6H5F (0 ppm) respectively, as external standards. All other reagents and solvents were obtained from commercial sources and used without further purification. GC-MS analysis was performed using an Agilent 7890B GC system equipped with the HP-5 Ultra Inert column (30 m, 0.25 mm, 0.25 μm), and an FID detector. For MS detection, an electron ionization system was used with an ionization energy of 70 eV. Elemental microanalyses were performed by Midwest Microlab, Indianapolis, IN. Synthesis of PPCF3P TMS-CF3 Under a nitrogen atmosphere, PPClP (1.37 g, 2.2 mmol) was dissolved in a minimal amount of THF (10 mL) in a 20 mL scintillation vial equpped with a stir bar and stirred at room temperature. To this stirring solution, KF (0.152 g, 2.6 mmol, 1.2 equiv), 18-crown-6 (0.115 g, 0.4 mmol, 0.2 equiv), and TMS-CF3 (0.341 g, 2.4 mmol, 1.1 equiv) was added and the reaction mixture warmed to 36 °C. Reaction progress was monitored by31P NMR for the disappearance of the PPClP starting material. Once the starting material has been completely consumed, the Attorney Docket No.103361-532WO1 excess KF is filtered off and discarded. The filtrate, upon partial drying rapidly forms a sticky off-white solid that becomes brittle upon complete drying. Once dry, the crude solids were dissolved in Et2O (3 mL) with stirring followed by the addition of n-pentane (15 mL) for several hours. Repeated washing of the precipitate followed by extraction of the supernatant liquid (enriched in undesired side-products) affords nearly pure PPCF3P as an white to off-white solid. Further purification by crystallization from a mixture of diethyl ether and pentane at -35 °C for several days yields pure target material in amorphous and crystalline form.1H{31P} NMR (400 MHz, C6D6) δ 7.37 – 7.28 (overlapping, 10H), 7.11 (dd, J = 7.6, 1.6, 2H), 7.09 – 6.98 (overlapping, 14H), 6.80 (dt, J = 7.5, 1.2 Hz, 2H), 3.78 (m, 2H), 3.03 (m, 2H).31P NMR (162 MHz, C6D6) δ 74.98 (tq, J = 44.0, 25.5, 18.6 Hz), -16.82 (dq, J = 69.2, 11.9 Hz).19F NMR (376 MHz, C6D6) δ -62.58 (dt, J = 44.5, 12.1 Hz).13C NMR (151 MHz, THF-d8) δ 149.9, 138.4, 138.3, 135.8, 134.8, 134.4, 130.9, 129.1, 129.0, 128.9, 126.2, 125.8, 54.3; Elemental Analysis C39H32N2P3F3, Calc: C, 69.03; H, 4.53; N, 4.13); Found: C, 68.99; H, 4.73; N, 4.11). Synthesis of (PPCF3P)CoI2(1) Under a nitrogen atmosphere, cobalt(II) iodide (0.303 g, 967 umol, 1.1 equiv) was suspended in THF (5 mL) in a 20 mL scintillation vial equipped with stir bar and stirred at room temperature. PPCF3P (0.300 g, 0.442 umol) was dissolved in THF (10 mL) then added to the stirring solution of cobalt(II) iodide. The color of the solution immediately took on a green- brown coloration. The reaction mixture was allowed to stir for 16 hours, during the course of which, the product, 1, precipitated from solution as a green solid. The green solid was then collected on a frit and washed with THF (2 x 10 mL), C6H6 (2 x 10 mL) and hexanes (20 mL), dried in vacuo before drying overnight to yield 1 as an analytically pure, golden-brown powder (0.786 g, 89.7%). Crystals of 1 suitable for X-ray diffraction were grown via slow evaporation of a concentrated CH2Cl2 solution of 1 at room temperature.1H NMR (400 MHz, CD2Cl2) δ 9.22 (br s), 8.41 (s), 7.70 (br s), 7.47 (br s), 5.57 (br s), 4.65 (br s), 2.57 (br s). Elemental Analysis C39H32N2P3CoF3I2, Calc: C, 47.25; H, 3.25; N, 2.83); Found: C, 47.33; H, 3.78; N, 2.89). Attorney Docket No.103361-532WO1 Synthesis of (PPCF3P)CoH(η2styrene) (2) Under an atmosphere of nitrogen, complex 1 (108.1 mg, 109 µmol) was loaded to a 20 mL scintillation vial equipped with a magnetic stir bar and C6H6(2 mL) added to afford a largely heterogeneous mixture which was gently mixed. To this mixture, using a micropipette, styrene (20 equiv, 250 µL, 2.18 mmol) was added followed by KBEt3H (1 M in THF, 218.1 μL, 2.0 equiv) which resulted in a yellow, turbid solution over the course of 60 minutes. The reaction mixture was then filtered and the filtrate concentrated. The resulting yellow and black residue was extracted into hexanes (18 mL) with vigorous stirring several times and these washings combined before filtration through a pipette filter. The collected yellow filtrate was concentrated to dryness to afford mostly pure 2 as a yellow powder. Crystals of 2 suitable for single-crystal XRD were obtained by slow crystallization of a saturated n-pentane solution at -35 °C over several weeks as bright yellow and needles.1H NMR (400 MHz, C6D6) δ 7.82 (d, J = 7.4 Hz, 2H), 7.63 (d, J = 7.4 Hz, 2H), 7.57 (d, J = 7.7 Hz, 1H), 7.17 – 6.75 (overlapping, 24H), 6.71 (t, J = 7.2 Hz, 1H), 6.63 (t, J = 7.3 Hz, 1H), 6.52 (t, J = 7.4 Hz, 3H), 3.92 (t, J = 10.0 Hz, 1H), 3.67 (m, 1H), 3.10 (m, 1H), 3.33 (m, 1H), 3.10 (d, J = 6.9 Hz, 1H), 2.72 (d, J = 11.7 Hz, 1H), 2.32 (m, 1H), 2.01 (m, 1H), -14.40 (d, J = 135.9 Hz, 1H).31P NMR (162 MHz, C6D6) δ 124.8, 46.00.19F NMR (376 MHz, C6D6) δ -62.58 (dt, J = 44.5, 12.1 Hz).13C (160 MHz, THF-D8) δ 149.9, 138.4, 135.8, 134.8, 134.4, 130.9, 129.1, 129.0, 128.9, 126.2, 125.8, 54.3. Elemental Analysis C47H41N2P3CoF3, Calc: C, 66.99; H, 4.90; N, 3.32); Found: C, 62.78; H, 5.11; N, 3.21) (Note: a satisfactory result was not obtained after three attempts using spectroscopically pure material. We attribute this to the transient stability of 2 under prolonged exposure to atmospheric conditions). Synthesis of (PPCF3P)CoI (3) Attorney Docket No.103361-532WO1 Under an atmosphere of nitrogen, complex 1 (72.0 mg, 73 μmol) was loaded to a 20 mL scintillation vial equipped with a stir bar and C6H6(5.0 mL) was added, the heterogenous mixture was then vigorously stirred. To this mixture, KC8(11.8 mg, 1.1 equiv) suspended in C6H6 (2.0 mL) was transferred to the reaction vial and stirring continued for 16 hours. The darkly colored solution was reduced to a volume of approximately 3 mL before being passed through a pipette filter followed by several washings with C6H6to ensure recovery of the desired product which exhibits sparing solubility in aromatic solvents. The combined filtrates were concentrated in vacuo to afford nearly pure 3 as a brown to biege amorphous solid. Washing with n-pentane followed by lyophilization from C6H6furnished analytically pure 3 in 66.9% yield (42.0 mg) as a beige to cream colored amorphous solid. Crystals of 3 suitable for X-ray diffraction were grown via vapor-diffusion of pentane into a saturated solution of 3 in THF at - 35 °C.1H NMR (400 MHz, C6D6) δ 17.93 (br s), 9.73 (br s), 9.16 (br s), 7.00 (br s), 3.26 (br s), 0.50 (br s), -0.71 (br s), -2.52 (br s), -2.67 (br s), -5.63 (br s), -9.33 (br s). Elemental Analysis C39H32N2P3CoF3I, Calc: C, 54.19; H, 3.73; N, 3.24); Found: C, 53.94; H, 3.71; N, 3.22). Synthesis of (PPCF3P)CoH(PMe3) (4) Complex 1 (21.4 mg, 22 µmol) was loaded to a 20 mL scintillation vial equipped with a magnetic stir bar and THF (4 mL) added to afford a heterogeneous mixture which was gently mixed. To this mixture, using a micropipette, KBEt3H (2.0 equiv, 1 M in THF, 43.2 µL) was added and the reaction mixture allowed to stir for three minutes before addition of PMe3 (3.0 equiv, 6.6 µL, 64.8 µmol) by micropette. The reaction mixture rapidly took on a vivid orange coloration and this was allowed to stir for 12 hours. Afterwhich time, the solution was filtered through a pipette filter with glass-wool filter paper and the filtrate concentrated to yield crude 4 as a dark-red residue. Crystallization of crude 4 from a sautrated solution of n-pentane at -35 °C affords the spectroscopically pure complex as an orange crystalline solid of single-crystal XRD quality (17.0 mg, 96.7%).1H NMR (400 MHz, C6D6) δ 7.79 (d, J = 7.90 Hz, H), 7.63 (d, J = 7.31 Hz, H), 7.46 (d, J = 7.60 Hz, H), 7.17 – 7.01 (m, overlapping, H), 6.88 – 6.68 (m, overlapping, H), 3.64 (m, 2H), 2.37 (m, 2H), 0.93, (s, 9H).19F NMR (376 MHz, C6D6) δ -64.17 Attorney Docket No.103361-532WO1 (d, J = 54.05 Hz). Elemental Analysis C47H41N2P3CoF3, Calc: C, 66.99; H, 4.90; N, 3.32); Found: C, 62.78; H, 5.11; N, 3.21. Hydroboration Conditions - Representative Procedure - 4,4,5,5-tetramethyl-2- phenethyl-1,3,2-dioxaborolane (5a)1 To an oven-dried 20 mL scintillation vial equipped with stir bar was added 1 (8.2 mg, 8.3 µmol, 0.1 mol%), styrene (0.86 g, 8.3 mmol), and HBpin (1.1 equiv, 9.1 mmol) and the resultant heterogenous mixture stirred. The activator, KBEt3H (100 mM in THF, 440 µL, 0.2 mol%) was added by micropippete, affording a yellow, homogenous solution which was stirred for 6 hours. It is noted that the solution gradually darkens and takes on an orange coloration as catalysis nears completion. The reaction vial was removed from the glovebox, exposed to air, and pentanes (3 mL) added to encourage precipitation of deactivated cobalt species with gentle stirring for approximately 15 minutes. The quenched mixture was then filtered through a pad of Celite (washing the filter several times with fresh solvent to extract the desired product) to remove insolube precipitates and the filtrate concentrated by rotary evaporation (water bath, c. 30 °C) to afford nearly pure 4,4,5,5-tetramethyl-2-phenethyl-1,3,2-dioxaborolane as a colorless, viscous oil. The product was further purified by column chromatography (silica, hexanes / EtOAc 9:1) affording the product as a white amorphous solid (1.81 g, 94.4% yield).1H NMR (400 MHz, C6D6): δ 7.22 – 7.12 (m, overlapping, 4H), 7.05 (tt, J = 7.07, 1.7 Hz, 1H), 2.88 (t, J = 7.9 Hz, 2H), 2.02 (t, J = 7.92H), 1.01 (s, 12H).11B NMR (128 MHz, C6D6): δ 34.1 (br s). The compounds, compositions, and methods of the appended claims are not limited in scope by the specific compounds, compositions, and methods described herein, which are intended as illustrations of a few aspects of the claims. Any compounds, compositions, and methods that are functionally equivalent are intended to fall within the scope of the claims. Various modifications of the compounds, compositions, and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative compounds, components, compositions, and method steps disclosed herein are specifically described, other combinations of the compounds, components, compositions, and method steps also are intended to fall within the scope of the appended Attorney Docket No.103361-532WO1 claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein or less, however, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated. The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. Although the terms “comprising” and “including” have been used herein to describe various embodiments, the terms “consisting essentially of” and “consisting of” can be used in place of “comprising” and “including” to provide for more specific embodiments of the invention and are also disclosed. Other than where noted, all numbers expressing geometries, dimensions, and so forth used in the specification and claims are to be understood at the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, to be construed in light of the number of significant digits and ordinary rounding approaches. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed invention belongs. Publications cited herein and the materials for which they are cited are specifically incorporated by reference.

Claims

Attorney Docket No.103361-532WO1 WHAT IS CLAIMED IS:

1. A metal complex defined by Formula I, Formula II, or Formula III belowFormula III wherein M is rhodium, iridium, cobalt, or iron; X is, individually for each occurrence, an anionic ligand; Y represents an alkene ligand; R1represents hydrogen, alkyl, haloalkyl, ORA, or NRA2;Attorney Docket No.103361-532WO1 R2and R2’represent, individually for each occurrence, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted with one or more substituents individually chosen from RB; or R2and R2′, together with the atoms to which they are attached, combine to form a 3 to 7 membered ring optionally substituted with one or more substituents individually chosen from RB; R3, R4, R5, and R6represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; R7, R7’, R8, and R8’represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RBRArepresents, individually for each occurrence, hydrogen, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; and RBrepresents, individually for each occurrence, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, and heterodialkylaminocarbonyl.

2. The metal complex of claim 1, wherein the complex is defined by Formula I.Attorney Docket No.103361-532WO1 3. The metal complex of claim 1, wherein the complex is defined by Formula II.

4. The metal complex of claim 1, wherein the complex is defined by Formula III.

5. The metal complex of claim 4, wherein the complex is defined by the formula belowFormula III wherein M is rhodium, iridium, cobalt, or iron; X is, individually for each occurrence, an anionic ligand; R1represents hydrogen, alkyl, haloalkyl, ORA, or NRA2; R2and R2’represent, individually for each occurrence, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted with one or more substituents individually chosen from RB; or R2and R2′, together with the atoms to which they are attached, combine to form a 3 to 7 membered ring optionally substituted with one or more substituents individually chosen from RB; R3, R4, R5, and R6represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB;Attorney Docket No.103361-532WO1 R7, R7’, R8, and R8’represent, individually for each occurrence, hydrogen, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, heterodialkylaminocarbonyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; RArepresents, individually for each occurrence, hydrogen, alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB; RBrepresents, individually for each occurrence, hydroxy, halogen, -CN, -NO2, amino, alkylamino, dialkylamino, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl, haloalkylsulfonyl, alkylcarbonyl, haloalkylcarbonyl, alkoxycarbonyl, haloalkoxycarbonyl, alkylaminocarbonyl, heteroalkylaminocarbonyl, dialkylaminocarbonyl, and heterodialkylaminocarbonyl; and RCand RC’individually represent hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloheteroalkyl, alkylaryl, alkylheteroaryl, alkylcycloalkyl, and alkylcycloheteroalkyl, each optionally substituted where valence permits with one or more substituents individually chosen from RB.

6. The metal complex of claim 4, wherein Y represents styrene.

7. The metal complex of any one of claims 1-6, wherein M is rhodium.

8. The metal complex of any one of claims 1-6, wherein M is iridium.

9. The metal complex of any one of claims 1-6, wherein M is cobalt.

10. The metal complex of any one of claims 1-6, wherein M is iron.

11. The metal complex of any one of claims 1-10, wherein R3, R4, R5, and R6represent hydrogen.Attorney Docket No.103361-532WO1 12. The metal complex of any one of claims 1-11, wherein R7, R7’, R8, and R8’represent hydrogen.

13. The metal complex of any one of claims 1-12, wherein R2and R2’represent, individually for each occurrence, alkyl, aryl, cycloalkyl, alkylaryl, or alkylcycloalkyl, each optionally substituted with one or more substituents individually chosen from RB.

14. The metal complex of any one of claims 1-13, wherein R2and R2’represent, individually for each occurrence, alkyl or aryl, each optionally substituted with one or more substituents individually chosen from RB.

15. The metal complex of any one of claims 1-14, wherein R2and R2’represent, individually for each occurrence, a C1-C6 alkyl group.

16. The metal complex of any one of claims 1-14, wherein R2and R2’represent, individually for each occurrence, an aryl group.

17. The metal complex of claim 16, wherein R2and R2’represent phenyl.

18. The metal complex of any one of claims 1-17, wherein R1represents an electron withdrawing group.

19. The metal complex of any one of claims 1-18, wherein R1represents a haloalkyl group.

20. The metal complex of any one of claims 1-18, wherein R1represents an alkoxy or haloalkoxy group.

21. The metal complex of any one of claims 1-20, wherein X represents halogen.

22. The metal complex of claim 21, wherein X represents I or Cl.

23. The metal complex of any one of claims 1-20, wherein X represents hydride or alkyl.Attorney Docket No.103361-532WO1 24. The metal complex of any of claims 1-23, wherein the metal complex comprises one of the following.

25. A catalytic process for hydroelementation of an olefin wherein the improvement comprises the metal complex of any of claims 1-24 as a catalyst.

26. The process of claim 25, wherein the process comprises a hydrogenation reaction, a hydroboration reaction, or a hydrosilylation reaction.