Zwitterionic allyl nickel complex, preparation method therefor, and use thereof

Abstract

The present invention provides a zwitterionic allyl nickel complex, a preparation method therefor, and a use thereof. The zwitterionic allyl nickel complex has a structure represented by formula (I); in formula (I), R1 and R1' are identical or different, and are each independently selected from C1-C4 alkyl and C6-C15 aralkyl, and R2 is selected from H and C1-C6 alkyl. The zwitterionic allyl nickel complex catalyzes copolymerization of ethylene and an acrylate monomer, the reaction conditions are mild, the catalytic activity is high, and the molecular weight of a product is high, thereby preparing a moderately branched ethylene-acrylate copolymer.

Description

A zwitterionic allyl nickel complex and its preparation method and application Technical Field

[0001] The present invention belongs to the field of catalysts, and in particular relates to a novel zwitterionic allyl nickel complex, a preparation method thereof, and use thereof in preparing an ethylene-methyl acrylate copolymer, and a corresponding preparation method of the ethylene-methyl acrylate copolymer. Background Art

[0002] Polyolefin materials are the most widely used polymer materials. Introducing polar groups into non-polar polyolefin chains can significantly improve the adhesion, dyeability, and compatibility of polyolefin materials. For example, industrial ethylene-methyl acrylate copolymers (EMA) with an ester content of 10ω%-30ω% and a branched structure have excellent mechanical properties and compatibility and are widely used in many fields. In industry, EMA is obtained through free radical copolymerization under harsh conditions of high temperature (150℃-300℃) and high pressure (150MPa-300MPa). Compared with harsh free radical copolymerization, the preparation of functionalized polyolefins by direct copolymerization of olefins and polar monomers under mild conditions through coordination polymerization is a simple, direct and effective method.

[0003] Late transition metal catalysts, particularly palladium catalysts, are widely used in the copolymerization of ethylene with polar monomers. Literature has reported that the copolymerization of ethylene and methyl acrylate (MA) catalyzed by α-diimine palladium typically produces highly branched copolymers with MA located at the ends of the branches due to the rapid chain propagation process. EMA prepared using α-diimine palladium catalysts, due to their high degree of branching, lacks a melting point, and has poor mechanical properties, making them unsuitable for use as thermoplastic resins. Furthermore, the copolymerization of ethylene and MA catalyzed by phosphinesulfonic acid palladium can produce highly linear EMA with MA inserted into the main chain. However, due to the lack of the branches of EMA prepared using the high-pressure free radical method, the material has poor toughness and elasticity.

[0004] Furthermore, because palladium is a precious metal and expensive, the copolymerization of ethylene and polar monomers using inexpensive and abundant nickel catalysts is more practical for industrial applications. However, due to the higher electrophilicity of the nickel metal center, the copolymerization of ethylene and MA to produce high-molecular-weight copolymers is often difficult. For example, α-diimine palladium can effectively catalyze the copolymerization of ethylene and methyl acrylate (MA), but α-diimine nickel catalysts are less effective. Therefore, the development of nickel catalysts with weak electrophilicity and the ability to achieve the copolymerization of ethylene and methyl acrylate (MA) through appropriate ligand design is of great significance. Developing nickel catalysts capable of producing moderately branched EMA requires a comprehensive balance of the electrophilicity of the metal center, enabling the copolymerization of polar acrylate monomers while also enabling chain walking to produce products with structures similar to those obtained from free-radical polymerization. This aspect has not yet been reported in the literature and holds great industrial significance.

[0005] CN112538098A discloses an α-sulfonic acid-β-diimine nickel complex, a preparation method, and its use as a catalyst in the copolymerization of ethylene and methyl acrylate. The structure of the nickel complex is as follows:

[0006] Ar is 2,6-diisopropylphenyl or 2,6-dimethylphenyl; X is chlorine or bromine. The temperature range for catalytic copolymerization of olefins and polar monomers is 0°C-80°C, and the molar ratio of catalyst to polar monomer is 1:100-1:2000. Using toluene as the solvent and MAO as the cocatalyst, the copolymerization activity of ethylene and methyl acrylate was 5.09×10-1 at a methyl acrylate concentration of 0.2 M, an aluminum-nickel molar ratio of 1500:1, an ester agent molar ratio of 266:1, an ethylene pressure of 0.5 MPa, at 50°C for 4 h. 3 g / molNi·h, the weight-average molecular weight of EMA is 41.9 kg / mol, the molecular weight distribution is 1.39, the ester content in EMA is 0.8 mol%, and the melting temperature is 98.5°C. This technology discloses a new catalyst for the copolymerization of ethylene and methyl acrylate, mainly used to prepare low-branched, semi-crystalline polyethylene. The alkyl group coordinated with nickel is acetonitrile and halogen. Under the condition that the molar ratio of the main catalyst to the co-catalyst reaches 1:1500-1:5000, the copolymerization activity is only 5.09×10 3 g / molNi·h.

[0007] CN1727372A discloses a β-diimine titanium catalyst containing halogen substituents for ethylene copolymerization, and its structure is as follows:

[0008] where R cis an aryl or halogenated alkyl group; X is an anionic coordinating group including a halogen, a hydrocarbon group, an aryl group, an oxygen-containing group, a nitrogen-containing group, wherein the oxygen-containing group is an oxypropylene group, an epoxy-fixed group, an epoxy-pentyl group or an acetylacetone group, in particular a secondary amine, preferably a di(C 1-16 Alkyl) amine; Aniline has at least one halogenated hydrocarbon group on the benzene ring, such as trifluoromethyl. Using toluene as solvent and MMAO as cocatalyst, the activity of ethylene and norbornene copolymerization at 0.1 MPa, 30°C, and 15 minutes was 3.9×10 3 g / molTi·h, and the norbornene content in the copolymer is 16.8%. This technology discloses a β-diimine titanium catalyst containing halogen substituents that can be used for the copolymerization of ethylene and norbornene. The alkyl group coordinated with titanium is an epoxide, and the copolymerization activity is only 3.9×10 3 g / molNi·h.

[0009] CN110483329A discloses a large sterically hindered ketimine nickel catalyst, the structure of which is as follows:

[0010] The negative ion in the catalyst is tetrakis(3,5-bis(trifluoromethyl)phenyl)borate anion. An allyl group attached to a nickel atom, wherein n is an integer of 50-500 and has a free radical Br at the distal end, can be used for the polymerization of methyl methacrylate, methyl acrylate, acrylonitrile, acrylamide, styrene, or N-vinyl pyrrolidone. No copolymerization data are given in this invention.

[0011] US6897272B1 discloses a catalyst for copolymerizing ethylene with alkenyl esters or carboxylic acids at 20°C-100°C to prepare polymers that can be used as elastomers, molding resins, adhesives, etc. The catalyst structure is as follows:

[0012] Catalyst XXXVII in this patent utilizes an α-diimine ligand with a specific structure, where M is nickel and A is an allyl or benzyl group. The allyl group consists of three adjacent sp2 carbon atoms bonded to the metal center in a π3 arrangement. These three sp2 carbon atoms can be substituted with other hydrocarbon groups or functional groups. Examples 200-203 provide methods for synthesizing allyl-coordinated diimine palladium catalysts, and Examples 497-515 provide methods for preparing nickel-coordinated diimine catalysts containing allyl substituents. However, no experimental polymerization data are published. This invention is an α-diimine nickel catalyst.

[0013] CN102105502A discloses a method for producing a diblock copolymer of a monovinyl aromatic polymer block, wherein the repeating units of A are selected from the residues of one or more aliphatic hydroxycarboxylic acids and one or more cyclic carbonates, the repeating units of B are selected from the residues of a monovinyl aromatic monomer, R and Y are derived from alcohols containing another functionalized group in addition to an -OH functional group to allow the polyvinyl aromatic compound to grow or graft, and R is a linking group. A bulky single-site β-diimine metal catalyst is used, and the structure is as follows:

[0014] where R 7 is hydrogen, a hydrocarbon group or an inert functional group and two or more of the groups can be linked to form a ring, X is C 1-12 The catalyst can be used as a catalyst for preparing HAORYB diblock copolymers. The patent discloses examples of polylactic acid-polystyrene copolymers. The invention primarily protects the product composition and does not disclose the catalyst's structural details.

[0015] US2005 / 0043496 discloses an α-diimine nickel catalyst for the copolymerization of ethylene and methyl acrylate, the structure of which is as follows:

[0016] The obtained polymer has C1 to C6 + The copolymerization of ethylene and methyl acrylate was catalyzed by catalyst No. 45 at 100°C-120°C, 6.9 MPa, 18 h, 0.0025 mmol of catalyst, 160 equivalents of B(C6F5)3, 80 equivalents of NaBAF, 0.5 mL of MA, and 9.5 mL of chlorobenzene to obtain 2.9 g and 2.59 g of polymers, respectively. The MA insertion rates were 0.53 mol% and 0.45 mol%, respectively. The weight-average molecular weights were 18706 g / mol and 10394 g / mol, respectively. The methyl branches accounted for 31.8% and 51.8%, respectively.

[0017] WO01 / 92347A2 discloses a [P,O]-type allyl nickel catalyst or a [P,N]-type allyl nickel catalyst for the copolymerization of ethylene and methyl acrylate. The catalyst can be used for the copolymerization of ethylene with aryl alkenoate or long-chain alkenoate. The catalyst structure is as follows:

[0018] CN1315573C discloses a β-diimine nickel catalyst dimer, the structure of which is as follows:

[0019] Wherein R1 and R2 are hydrogen, alkyl, aryl, alkenyl or alkylsilyl, Ar1 and Ar2 are 2,6-dimethylphenyl or 2,6-diisopropylphenyl, X is Cl, Br or I, and the molar ratio of the main catalyst to the cocatalyst is 1:10-1:40. Using toluene as the solvent and triethylaluminum as the cocatalyst, the copolymerization activity of ethylene and methyl methacrylate is 6.6×10-1 under the conditions of methyl methacrylate concentration of 0.015M, aluminum-nickel molar ratio of 20:1, ethylene pressure of 0.8 MPa, 20°C, and 2h. 4 g / molNi·h, the weight-average molecular weight of EMMA is 150 kg / mol, and the ester content in EMA is 0.7 mol%. The catalyst can be used for the copolymerization of ethylene and methyl methacrylate, with the molar ratio of the main catalyst to the co-catalyst being 1:10-1:40, but the copolymerization activity is not high.

[0020] CN113680389A discloses a multidentate β-diimine rare earth metal catalyst, the structure of which is as follows:

[0021] The catalyst is primarily used to prepare carbamate compounds or 2-oxazolidinone compounds. Carbamate compounds are important pesticide and pharmaceutical intermediates. 2-Oxazolidinone compounds are important heterocyclic compounds that have attracted much attention in antibacterial, anti-inflammatory, anti-cancer and anti-tuberculosis applications.

[0022] CN105646756B discloses an α-diimine nickel catalyst, the structure of which is as follows:

[0023] wherein Z and Y are each a C1-C4 alkyl group, or Z and Y together with the carbon-carbon single bond connected thereto constitute an unsubstituted or substituted group selected from the group consisting of acenaphthenyl, phenanthrenyl, camphenyl and C5-C8 cycloalkyl; R 1 、R 2 R is H, halogen, C1-C8 alkyl, C1-C8 haloalkyl, phenyl, benzyl, -O-Ra, -CH2-O-Ra, -SRb or -CH2-S-Rb; 3 and R 4 are H, halogen, C1-C8 alkyl, C1-C8 haloalkyl, -O-Ra, -CH2-O-Ra, -SRb or -CH2-S-Rb, wherein Ra and Rb are C1-C8 alkyl, phenyl, benzyl, and R 1 、R 2 、R 3 and R 4 Satisfied conditions: R 1 ≠R 3 and / or R 2 ≠R 4The X coordinated with nickel can be an allyl group, a halogen, a C1-C4 alkyl group, a C2-C6 alkenyl group, or a benzyl group. The catalyst can catalyze the copolymerization of ethylene with long-chain alcohols, long-chain methoxy compounds, and the like to produce high-end lubricants.

[0024] Summary of the Invention

[0025] In order to solve the above problems, the purpose of the present invention is to provide a zwitterionic allyl nickel complex and its preparation method and application. The zwitterionic allyl nickel complex catalyzes the copolymerization of ethylene and acrylate monomers with mild reaction conditions, high catalytic activity, and high product molecular weight, and can prepare moderately branched ethylene-acrylate copolymers.

[0026] In order to achieve the above object, the present invention provides a zwitterionic allyl nickel complex having a structure shown in Formula I:

[0027] In formula I, R1 and R1' are the same or different and are independently selected from C1-C4 alkyl, C6-C 15 R2 is selected from H, C1-C6 alkyl.

[0028] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are the same or different and are independently selected from methyl, isopropyl, and benzhydryl; and R2 is selected from hydrogen and methyl.

[0029] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are the same.

[0030] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are both methyl, and R2 is hydrogen; or, R1 and R1' are both isopropyl, and R2 is hydrogen; or, R1 and R1' are both benzhydryl, and R2 is methyl.

[0031] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are both isopropyl, and R2 is hydrogen.

[0032] The present invention also provides a method for preparing the above-mentioned zwitterionic allyl nickel complex, which comprises the following steps:

[0033] α-sulfonic acid-β-diimine lithium salt compound and allyl nickel precursor The mixed reaction is performed to obtain the zwitterionic allyl nickel complex, and the reaction process is as follows:

[0034] According to a specific embodiment of the present invention, preferably, the above preparation method comprises the following steps:

[0035] (1) reacting a β-diimine compound with n-BuLi and SO3.NMe3 (trimethylammonium sulfur trioxide copolymer) to obtain an α-sulfonic acid-β-diimine lithium salt compound; (2) mixing the α-sulfonic acid-β-diimine lithium salt compound with an allyl nickel precursor to obtain the zwitterionic allyl nickel complex, and the reaction process is as follows;

[0036] According to a specific embodiment of the present invention, the above preparation method comprises the following specific steps:

[0037] (1) dissolving a β-diimine compound in tetrahydrofuran, adding n-BuLi dropwise at a temperature below -78°C (≤-78°C), stirring, heating to room temperature, and continuing to stir; then cooling to below -78°C (≤-78°C), adding SO3.NMe3, heating to room temperature, and continuing to stir to obtain an α-sulfonic acid-β-diimine lithium salt compound, wherein the molar ratio of the β-diimine compound, n-BuLi, and SO3.NMe3 is preferably 1:1:1; (2) stirring the α-sulfonic acid-β-diimine lithium salt compound and an allyl nickel precursor in dichloromethane to obtain the zwitterionic allyl nickel complex.

[0038] The present invention also provides a catalyst system, which comprises a main catalyst and an activator. The main catalyst comprises the above-mentioned zwitterionic allyl nickel complex.

[0039] According to a specific embodiment of the present invention, preferably, the molar ratio of the main catalyst to the activator is 1:5-1:100, more preferably 1:40-1:80.

[0040] According to a specific embodiment of the present invention, preferably, the activator includes one or a combination of two or more of methylaluminoxane (MAO), modified methylaluminoxane (MMAO), diethylaluminum monochloride, ethylaluminum dichloride, triisobutylaluminum, and tris(pentafluorophenyl)borane.

[0041] According to a specific embodiment of the present invention, preferably, the activator includes methylaluminoxane (MAO) or a combination of tris(pentafluorophenyl)borane and triisobutylaluminum (TIBA).

[0042] The present invention also provides a method for copolymerizing ethylene and acrylic ester, which comprises the following steps: using the above-mentioned zwitterionic allyl nickel complex or the above-mentioned catalyst system to catalyze the copolymerization reaction of ethylene and acrylic ester to obtain a branched ethylene-acrylic ester copolymer.

[0043] According to a specific embodiment of the present invention, preferably, the acrylic ester includes one or a combination of two or more of methyl acrylate, ethyl acrylate, butyl acrylate, and tert-butyl acrylate.

[0044] According to a specific embodiment of the present invention, preferably, the acrylate includes methyl acrylate and / or ethyl acrylate.

[0045] According to a specific embodiment of the present invention, preferably, the polymerization temperature is 0°C-100°C, more preferably 30°C-80°C.

[0046] According to a specific embodiment of the present invention, preferably, in the catalyst system, the molar ratio of the main catalyst to the acrylic ester is 1:266-1:1066, more preferably 1:266-1:533.

[0047] According to a specific embodiment of the present invention, preferably, the pressure of ethylene is 0.1 MPa-5.0 MPa, more preferably 0.5 MPa-3.0 MPa.

[0048] According to a specific embodiment of the present invention, preferably, the solvent used in the polymerization includes one or a combination of two or more of toluene, hexane, cyclohexane, and heptane. More preferably, the solvent used in the polymerization is toluene and cyclohexane.

[0049] The present invention also provides an ethylene-acrylate copolymer prepared by the above copolymerization method, which has a branching degree of 28 / 1000C-46 / 1000C, a melting temperature of 84.6°C-108.3°C, certain toughness and elasticity as well as adhesion, dyeability, and compatibility, and has broad application prospects.

[0050] According to a specific embodiment of the present invention, preferably, the weight average molecular weight of the ethylene-acrylate copolymer is 1×10 5 g / mol-1×10 6 g / mol (e.g., 1×10 5 g / mol≤weight average molecular weight<1×10 6 g / mol), and a molecular weight distribution of 1.31-2.33; in the ethylene-acrylate copolymer, the acrylate content is 3.50mol%-8.99mol%, and the alkyl branch content is 30 / 1000C-40 / 1000C; the melting temperature of the ethylene-acrylate copolymer is 84.6°C-98.3°C.

[0051] The zwitterionic allyl nickel complex of the present invention overcomes the defects or deficiencies of the existing palladium catalysts, such as high price, low polymerization activity, and the inability of the existing nickel catalyst system to prepare moderately branched ethylene-acrylate copolymers with excellent toughness and elasticity. The zwitterionic allyl nickel complex can be used as a main catalyst to catalyze the copolymerization of ethylene and acrylate monomers under the action of an activator to prepare branched ethylene-acrylate copolymer materials. On the one hand, the zwitterionic allyl nickel complex can reduce the electrophilicity of the nickel metal center due to the presence of a weak positive and negative ion interaction, thereby improving the performance of its copolymerized acrylate monomers. On the other hand, the nickel metal center still remains a cationic center, which can maintain weak chain walking ability and prepare moderately branched ethylene-acrylate copolymers. The use of the zwitterionic allyl nickel catalyst of the present invention to catalyze the copolymerization of ethylene and acrylate monomers has mild reaction conditions, high catalytic activity, and high product molecular weight, and has obvious technical advantages and industrial application prospects for the preparation of ethylene-acrylate copolymers by low-pressure coordination polymerization.

[0052] The present invention has the following beneficial effects:

[0053] 1. The zwitterionic allyl nickel complex provided by the present invention exists in the form of intramolecular cationic and anionic salts. The metal center is an alkylated cationic active center capable of olefin coordination polymerization. The required amount of expensive activating agent is small, and industrial production has significant economic benefits.

[0054] 2. The zwitterionic allyl nickel catalyst provided by the present invention can reduce the electrophilicity of the nickel metal center and improve the tolerance to polar groups due to the presence of a weak interaction between positive and negative ions, thereby significantly improving the copolymerization activity of ethylene and acrylate monomers;

[0055] 3. The zwitterionic allyl nickel catalyst provided by the present invention has a nickel metal center that still maintains a cationic center, thus having weak chain walking ability and can prepare branched ethylene-acrylate copolymers similar to those produced by the high-pressure method, showing promising industrial application prospects.

[0056] 4. The zwitterionic allyl nickel catalyst provided by the present invention catalyzes the copolymerization of ethylene and acrylate. Compared with industrial high-pressure free radical polymerization, it has obvious technical advantages such as mild reaction conditions, simple process equipment, and easier control of polymer structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG1 is a single crystal structure diagram of the zwitterionic allyl nickel complex provided in Example 8;

[0058] FIG2 is a hydrogen nuclear magnetic spectrum of ethylene-methyl acrylate (EMA) provided in Example 11;

[0059] FIG3 is a DSC analysis chart of ethylene-methyl acrylate (EMA) provided in Example 11. DETAILED DESCRIPTION

[0060] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0061] In the following examples, experimental methods without specific conditions are generally carried out in accordance with conventional conditions in the art or conditions recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from conventional markets.

[0062] In order to clearly describe the compounds and complexes in the examples, the following are described:

[0063] Formula III shows a β-diimine compound:

[0064] β-diimine compound A1, R1 and R1' are both methyl groups, and R2 is hydrogen;

[0065] β-diimine compound A2, R1 and R1' are both isopropyl, and R2 is hydrogen;

[0066] In the β-diimine compound A3, R1 and R1' are both benzhydryl and R2 is methyl.

[0067] Formula II shows an α-sulfonic acid-β-diimine lithium salt compound:

[0068] α-sulfonic acid-β-diimine lithium salt compound L1, R1 and R1' are both methyl groups, and R2 is hydrogen;

[0069] α-sulfonic acid-β-diimine lithium salt compound L2, R1 and R1' are both isopropyl, and R2 is hydrogen;

[0070] In the α-sulfonic acid-β-diimine lithium salt compound L3, R1 and R1' are both diphenylmethyl, and R2 is methyl.

[0071] Formula I shows a zwitterionic allyl nickel complex:

[0072] In the zwitterionic allyl nickel complex Ni-1, R1 and R1' are both methyl groups, and R2 is hydrogen;

[0073] In the zwitterionic allyl nickel complex Ni-2, R1 and R1' are both isopropyl, and R2 is hydrogen;

[0074] In the zwitterionic allyl nickel complex Ni-3, R1 and R1' are both diphenylmethyl, and R2 is methyl.

[0075] The synthesis route of the zwitterionic allyl nickel complex in the embodiment is as follows:

[0076] 1. Preparation of ligands

[0077] Example 1

[0078] This embodiment provides a 2,6-dimethylphenyl-substituted β-diimine compound A1, the synthesis method of which is as follows:

[0079] A round-bottom flask was sequentially charged with acetylacetone (4.1 g, 41 mmol), 2,6-dimethylaniline (15.1 g, 85.2 mmol), ethanol (500 mL), and hydrochloric acid (12 M, 6 mL). The system was heated to 100°C in an oil bath and allowed to react for 72 hours. The solution was then cooled to room temperature and the solvent removed by rotary evaporation to yield a brown solid. The solid was dissolved in dichloromethane (300 mL) and washed twice with saturated NaHCO₃ solution. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the filtrate was collected. The filtrate was then rotary evaporated to yield the crude product, which was recrystallized from methanol to yield a white solid. The yield was 87.5%. The H NMR spectrum is as follows: 1 H NMR(CDCl3,400MHz)δ(ppm):12.19(s,1H,NH)),7.03(d,4H,Ar-H),6.95(d,2H,Ar-H),4.88(s,1H,H β ),2.16(s,12H,CH3),1.69(s,6H,CH3).

[0080] Example 2

[0081] This embodiment provides a 2,6-diisopropylphenyl-substituted β-diimine compound A2, the synthesis method of which is as follows:

[0082] A round-bottom flask was sequentially charged with acetylacetone (4.1 g, 41 mmol), 2,6-diisopropylaniline (10.3 g, 85.2 mmol), ethanol (500 mL), and hydrochloric acid (12 M, 6 mL). The system was heated to 100°C in an oil bath and allowed to react for 72 hours. The solution was then cooled to room temperature and the solvent removed by rotary evaporation to yield a brown solid. The resulting solid was dissolved in dichloromethane (300 mL) and washed twice with saturated NaHCO₃ solution. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the filtrate was collected. The filtrate was then rotary evaporated to yield the crude product, which was recrystallized from methanol to yield a white solid. The yield was 86.2%. The H NMR spectrum is as follows: 1H NMR (CDCl3, 400MHz) δ (ppm): 12.11 (s, 1H, NH), 7.13 (m, 6H, Ar-H), 4.87 (s, 1H, H) β ),3.08(s,4H,CHMe2),1.72(s,6H,CH3),1.21(d,12H, CH(CH3)2),1.11(d,12H,CH(CH3)2).

[0083] Example 3

[0084] This embodiment provides a 2,6-benzhydryl 4-methylphenyl substituted β-diimine compound A3, the synthesis method of which is as follows:

[0085] A round-bottom flask was charged with acetylacetone (2.0 g, 20 mmol), 2,6-diphenylmethyl-4-methylaniline (19.3 g, 44 mmol), toluene (300 mL), and p-toluenesulfonic acid (12 M, 6 mL). The system was heated to 120°C in an oil bath and allowed to react for 5 days. The solution was then cooled to room temperature and the solvent removed by rotary evaporation to yield a brown solid. The solid was dissolved in dichloromethane (300 mL) and washed twice with saturated NaHCO₃ solution. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the filtrate was collected. The filtrate was then rotary evaporated to yield the crude product, which was recrystallized from methanol to yield a white solid. The yield was 52.7%. The H NMR spectrum is as follows: 1 H NMR (CDCl3, 400MHz) δ (ppm): 12.10 (s, NH, 1H), 7.26 (d, J = 4.3Hz, Ar-H, 16H), 7.15–6.95 (m, Ar-H, 24 H),6.84(s,Ar-H,4H),5.94(s,CH(Ph)2,4H),4.16(s,CHNH,1H),2.23(s,CH3,6H),0.23(s,CH3,6H).

[0086] Example 4

[0087] This embodiment provides an α-sulfonic acid-β-diimine lithium salt compound L1, the synthesis method of which is as follows:

[0088] Under a nitrogen atmosphere, β-diimine compound A1 (2.88 g, 9.24 mmol) was dissolved in dry tetrahydrofuran. n-BuLi (4.3 mL, 10.75 mmol) was slowly added dropwise at -78°C. After stirring at -78°C for 1 hour, the resulting system was slowly warmed to room temperature and stirred for 30 minutes. The temperature was then cooled to -78°C, and SO₃.NMe₃ (0.84 g, 6.04 mmol) was added. The temperature was slowly warmed to room temperature and stirred for 24 hours. The solution was filtered, the filtrate was concentrated, and frozen at -30°C to obtain a white precipitate. Filter the resulting white solid, wash twice with n-hexane, and dry in vacuo to obtain a white solid with a yield of 75.6%. The H NMR spectrum is as follows: 1 H NMR(DMSO-d6,400MHz)δ(ppm):7.04-6.87(m,6H,Ar-H),5.04(s,1H,H β ),3.72(m,8H,THF),2.08(s,6H,CH3),2.05(m,6H,CH3),1.81(m,8H,THF).

[0089] Example 5

[0090] This embodiment provides an α-sulfonic acid-β-diimine lithium salt compound L2, the synthesis method of which is as follows:

[0091] Following the synthesis method of Example 4, β-diimine compound A1 was replaced with β-diimine compound A2 to obtain a white solid with a yield of 83.7%. The H NMR spectrum is as follows: 1 H NMR(DMSO-d6,400MHz)δ(ppm):7.13-7.02(m,6H,Ar-H),5.04(s,1H,H β ),3.72(m,8H,THF),3.09(m,4H,CHMe2),2.09(s,6H,CH3),1.86(m,8H,THF),1.15(m,24H,CH(CH3)2).

[0092] Example 6

[0093] This embodiment provides an α-sulfonic acid-β-diimine lithium salt compound L3, the synthesis method of which is as follows:

[0094] Following the synthesis method of Example 4, β-diimine compound A1 was replaced with β-diimine compound A3 to obtain a white solid with a yield of 72.8%. The H NMR spectrum is as follows: 1H NMR(DMSO-d6,400MHz)δ(ppm):7.29 (d,16H,Ar-H),7.08-6.91(m,24H,Ar-H),6.76(s,4H,Ar-H),5.94(s,4H,CH(Ph)2),4.58(s,1H,H β ),3.72(m,8H,THF),2.28(s,6H,CH3),1.89(m,8H,THF),0.23(s,6H,CH 3) .

[0095] 2. Preparation of zwitterionic allyl nickel complexes

[0096] Example 7

[0097] This embodiment provides a zwitterionic allyl nickel complex Ni-1, the synthesis method of which is as follows:

[0098] Under nitrogen atmosphere, α-sulfonic acid-β-diimine lithium salt compound L1 (0.97 g, 1.77 mmol), allyl nickel (II) chloride dimer (0.53 g, 1.95 mmol), and dichloromethane (20 mL) were added sequentially to a Schlenk flask with a branch. The mixture was stirred at room temperature for 24 hours. The filtrate was filtered, concentrated, and n-hexane was added to precipitate. The precipitate was filtered, washed twice with n-hexane, and dried in vacuo to obtain a yellow powder. The yield was 81.3%. Elemental analysis (C 25 H 36 N2O3SNi (%) theoretical values: C, 59.66; H, 7.21; N, 5.57. Found values: C, 59.41; H, 7.08; N, 5.46. The H NMR spectrum is as follows: 1 H NMR(CDCl3,400MHz)δ(ppm):6.94-6.77(m,6H,Ar-H),5.48(dt,allyl-CH,1H),5.31(s,1H,H β ),2.08(s,1H,CH3),2.05(m,6H,CH3),1.96(d,allyl-CH2,2H). ESI-MS(m / z): 444.13[M-C3H5] + .

[0099] Example 8

[0100] This embodiment provides a zwitterionic allyl nickel complex Ni-2, the synthesis method of which is as follows:

[0101] The α-sulfonic acid-β-diimide lithium salt compound L2 was reacted with allyl nickel chloride (II) dimer. The remaining specific steps were the same as those in Example 7, with a yield of 71.8%. The single crystal structure is shown in Figure 1. Elemental analysis (C 32 H 50 Theoretical values ​​for N2O3SNi (%): C, 64.39; H, 8.52; N, 4.55. Found: C, 64.21; H, 8.44; N, 4.50. The H NMR spectrum is as follows: 1 H NMR(CDCl3,400MHz)δ(ppm):7.23(s,Ar-H,6H),5.61(dt,allyl-CH,1H),5.36(s,NHCH,1H),3.55(dt,CH(CH3)2,4H) ,2.19(s,CH3,6H),2.01(d,allyl-CH2,2H),1.46(d,CH(CH3)2,6H),1.22(d,CH(CH3)2,12H),1.09(d,CH(CH3)2,6H). ESI-MS(m / z):556.31[M-C3H5] + .

[0102] Example 9

[0103] This embodiment provides a zwitterionic allyl nickel complex Ni-3, the synthesis method of which is as follows:

[0104] The α-sulfonic acid-β-diimide lithium salt compound L3 was reacted with allyl nickel chloride (II) dimer to obtain the product. The remaining specific steps were the same as those in Example 7, with a yield of 68.8%. Elemental analysis (C 57 H 72 N2O3SNi, %) theoretical values: C, 79.01; H, 6.37; N, 2.46. Found values: C, 78.89; H, 6.28; N, 2.33. 1 H NMR(DMSO-d6,400MHz)δ(ppm):7.43(d,16H,Ar-H),7.21-7.09(m,24H,Ar-H),6.78(s,4H,Ar-H),6.33(s,4H,CH(Ph)2),5.85(dt,allyl-CH,1H),4.89(s,1H,H β ),2.36(d,allyl-CH2,2H)2.28(s,6H,CH3),0.33(s,6H,CH3). ESI-MS(m / z):1080.22[M-C3H5] + .

[0105] 3. Copolymerization of ethylene and acrylate monomers

[0106] In the following examples, the catalytic activity was calculated based on the mass of the final copolymer obtained, the amount of metal nickel catalyst used, and the polymerization time. The weight-average molecular weight of the prepared polyolefin was measured by gel permeation chromatography, the melting point of the polymer was measured by differential scanning calorimetry, and the polar monomer insertion rate was calculated by H-NMR spectroscopy.

[0107] Example 10-37 provides a method for preparing an ethylene-acrylate copolymer by copolymerizing ethylene and acrylate using a nickel catalyst. The specific reaction steps are as follows:

[0108] The autoclave was heated to 150°C and evacuated for 2 hours. After cooling to room temperature under vacuum, ethylene was repeatedly replaced three times. A predetermined amount of acrylic acid ester, an activator, and 30 μmol of zwitterionic allyl nickel catalyst were added to the autoclave. Finally, dry toluene was added to maintain a total volume of 40 mL. Ethylene was introduced at a predetermined pressure and polymerization was carried out at a predetermined temperature for 4 hours. After the polymerization time reached the set value, the ethylene addition was stopped, the pressure was slowly released, the autoclave was opened, and the reaction system was terminated with a 5% (v / v) hydrochloric acid-ethanol solution. The product was soaked in hydrochloric acid / ethanol, filtered, and washed several times with anhydrous ethanol. The polymer was then dried in a vacuum drying oven at 60°C to constant weight.

[0109] H NMR spectra of the polymer samples were measured using a Bruker Advance III 500 MHz NMR spectrometer (USA) at 120°C. The deuterated reagent was deuterated o-dichlorobenzene (o-C6D4Cl2), the sample tubes used were 5 mm NMR tubes, and tetramethylsilane (TMS) was used as the internal standard. The measurements were performed at a tilt angle of 74°, a delay time of 4 s, and a sampling time of 1.5 s. The proton decoupling method was used for the determination.

[0110] The branching degree of the polymer sample was calculated by high temperature hydrogen spectrum as follows:

[0111] The insertion rate of methyl acrylate (MA) in the polymer was calculated using the following method:

[0112] The insertion rate of the polar monomer is calculated by the ratio of the integrated areas of the H-NMR spectrum. The calculation formula is as follows:

[0113] The molecular weight (Mw) and molecular weight distribution (PDI = Mw / Mn) of the polymers were determined using a high-temperature gel permeation chromatography (GPC) PL-220. The GPC PL-220 was equipped with two analytical columns (USA PLgel 10μm MIXED-B) and a differential refractive index detector (RI). The GPC calibration curve used narrow-distribution polystyrene (PS) as the standard. Sample testing conditions were: the solvent and mobile phase were 1,2,4-trichlorobenzene (to which 0.125‰ of the antioxidant BHT was added), the GPC mobile phase flow rate was 1.0 mL / min, the test temperature was 150°C, and the polymer sample concentration was 0.5 mg / mL.

[0114] The polymer melting temperature was measured using a PerkinElmer DSC-4000 differential scanning calorimeter. Under a nitrogen atmosphere, the temperature was raised from -30°C to 200°C at a rate of 10°C / min, held for 3 minutes, then lowered to -30°C at a rate of 10°C / min, held for 3 minutes, and finally raised to 200°C at a rate of 10°C / min. The polymer melting point was determined using a secondary heating curve.

[0115] Examples 10-12 provide the results of the copolymerization of ethylene and methyl acrylate to prepare EMA using various zwitterionic allyl nickel catalysts. Specific reaction conditions and polymerization results are shown in Table 1.

[0116] Table 1 Results of copolymerization of ethylene and methyl acrylate catalyzed by different nickel catalysts

[0117] Polymerization conditions: 30 μmol of zwitterionic allyl nickel catalyst, activator MAO, Al / Ni=80:1, ethylene pressure 0.5 MPa, MA concentration 0.2 M, molar ratio of polar monomer (acrylate) to zwitterionic allyl nickel catalyst 266:1, solvent toluene, temperature 50°C, polymerization time 1 h.

[0118] It can be seen from Table 1 that under the same polymerization conditions, Ni-2 has the highest activity and the EMA copolymer has the highest molecular weight.

[0119] Examples 13-16 provide the results of the copolymerization of ethylene and methyl acrylate to prepare EMA using a zwitterionic allyl nickel catalyst Ni-2 in the presence of different activators. Specific reaction conditions and polymerization results are shown in Table 2.

[0120] The H NMR spectrum of ethylene-methyl acrylate (EMA) obtained in Example 11 is shown in FIG2 , and the DSC analysis chart is shown in FIG3 .

[0121] Table 2 Results of catalytic copolymerization of ethylene and methyl acrylate under different activator types

[0122] Polymerization conditions: zwitterionic allyl nickel catalyst Ni-2 30 μmol, Al / Ni=80:1, ethylene pressure 0.5 MPa, MA concentration 0.2 M, molar ratio of polar monomer to zwitterionic allyl nickel catalyst 266:1, solvent toluene, temperature 50°C, polymerization time 1 h.

[0123] Examples 17-21 provide the results of the copolymerization of ethylene and methyl acrylate to prepare EMA using a zwitterionic allyl nickel catalyst Ni-2 at different activator / Ni ratios. Specific reaction conditions and polymerization results are shown in Table 3.

[0124] Table 3 Results of catalytic copolymerization of ethylene and methyl acrylate under different activator ratios

[0125] Polymerization conditions: zwitterionic allyl nickel catalyst Ni-2 30 μmol, activator MAO, ethylene pressure 0.5 MPa, MA concentration 0.2 M, molar ratio of polar monomer to zwitterionic allyl nickel catalyst 266:1, solvent toluene, temperature 50°C, polymerization time 1 h.

[0126] Examples 22 and 23 provide the results of preparing EMA by copolymerizing ethylene and methyl acrylate using a zwitterionic allyl nickel catalyst Ni-2 at different MA monomer concentrations (MA / Ni). Specific reaction conditions and polymerization results are shown in Table 4.

[0127] Table 4 Results of catalytic copolymerization of ethylene and methacrylic acid at different MA concentrations

[0128] Polymerization conditions: zwitterionic allyl nickel catalyst Ni-2 30 μmol, activator MAO, Al / Ni=80:1, ethylene pressure 0.5 MPa, solvent toluene, temperature 50° C., polymerization time 1 h.

[0129] Examples 24-27 provide the results of preparing EMA by copolymerizing ethylene and methyl acrylate using a zwitterionic allyl nickel catalyst Ni-2 at different temperatures. Specific reaction conditions and polymerization results are shown in Table 5.

[0130] Table 5 Results of catalytic copolymerization of ethylene and methacrylic acid at different temperatures

[0131] Polymerization conditions: zwitterionic allyl nickel catalyst Ni-2 30 μmol, activator MAO, Al / Ni=80:1, ethylene pressure 0.5 MPa, MA concentration 0.2 M, molar ratio of polar monomer to zwitterionic allyl nickel catalyst 266:1, solvent toluene, polymerization time 1 h.

[0132] Examples 28-31 provide the results of preparing EMA by copolymerization of ethylene and methyl acrylate using a zwitterionic allyl nickel catalyst Ni-2 at different ethylene pressures. Specific reaction conditions and polymerization results are shown in Table 6.

[0133] Table 6 Results of catalytic copolymerization of ethylene and methacrylic acid under different ethylene pressures

[0134] Polymerization conditions: zwitterionic allyl nickel catalyst Ni-2 30 μmol, activator MAO, Al / Ni=80:1, MA concentration 0.2 M, molar ratio of polar monomer to zwitterionic allyl nickel catalyst 266:1, solvent toluene, temperature 50°C, polymerization time 1 h.

[0135] Examples 32-34 provide the results of preparing EMA by copolymerizing ethylene and methyl acrylate using a zwitterionic allyl nickel catalyst Ni-2 in different solvents. Specific reaction conditions and polymerization results are shown in Table 7.

[0136] Table 7 Results of catalytic copolymerization of ethylene and methacrylic acid under different solvents

[0137] Polymerization conditions: zwitterionic allyl nickel catalyst Ni-2 30 μmol, activator MAO, Al / Ni=80:1, ethylene pressure 0.5 MPa, MA concentration 0.2 M, molar ratio of polar monomer to zwitterionic allyl nickel catalyst 266:1, temperature 50°C, polymerization time 1 h.

[0138] Examples 35-37 provide the results of copolymerization of ethylene with different acrylate monomers catalyzed by zwitterionic allyl nickel catalyst Ni-2. Specific reaction conditions and polymerization results are shown in Table 8.

[0139] Table 8 Results of copolymerization of ethylene with different acrylate monomers

[0140] Polymerization conditions: zwitterionic allyl nickel catalyst Ni-2 30 μmol, activator MAO, Al / Ni = 80:1, ethylene pressure 5 MPa, polar monomer concentration 0.2 M, molar ratio of polar monomer to zwitterionic allyl nickel catalyst 266:1, solvent toluene, temperature 50°C, polymerization time 1 h.

[0141] In order to more clearly demonstrate the beneficial effects of the catalyst of the present invention, a structurally similar β-diimine nickel catalyst (Ni-0) was used to catalyze ethylene copolymerization as a comparative example. β-diimine nickel was synthesized according to the method reported in Organometallics 1997, 16, 1514, and its structure is:

[0142] The synthesis method is as follows:

[0143] (1) Preparation of β-diimine compound: The same as in Example 2: Acetylacetone (4.1 g, 41 mmol), 2,6-diisopropylaniline (10.3 g, 85.2 mmol), ethanol (500 mL) and hydrochloric acid (12 M, 6 mL) were added to a round-bottom flask in sequence; the system was heated to 100°C in an oil bath and reacted for 72 h. The solution was then cooled to room temperature and the solvent was removed by rotary evaporation to obtain a brown solid. The obtained solid was dissolved in dichloromethane (300 mL) and washed and extracted twice with saturated NaHCO3 solution. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the filtrate was collected; the filtrate was then rotary evaporated to obtain a crude product, which was recrystallized from methanol to obtain a white solid. Yield: 86.2%. The H NMR spectrum is as follows: 1H NMR (CDCl3, 400MHz) δ (ppm): 12.11 (s, 1H, NH), 7.13 (m, 6H, Ar-H), 4.87 (s, 1H, H β ),3.08(s,4H,CHMe2),1.72(s,6H,CH3),1.21(d,12H,CH(CH3)2),1.11(d,12H,CH(CH3)2);

[0144] (2) Preparation of β-diimine nickel bromide: Under a nitrogen atmosphere, β-diimine (1.77 mmol), nickel (II) bromide (1.95 mmol) and dichloromethane (20 mL) obtained in step (1) were added sequentially to a Schlenk flask with a branched port. The mixture was stirred at room temperature for 24 h. The filtrate was filtered and concentrated. N-hexane was added to precipitate the precipitate, which was filtered and washed twice with n-hexane. The precipitate was dried under vacuum to obtain the target product.

[0145] Comparative Example 1

[0146] In this comparative example, 30 μmol of the β-diimine nickel catalyst Ni-0 was used in place of the zwitterionic allyl nickel catalyst Ni-2 to copolymerize ethylene monomer and methyl acrylate. The polymerization method was the same as that for the copolymerization of ethylene and methyl acrylate in Example 11. No solid polymer was obtained in this polymerization. The β-diimine nickel copolymerization activity in this comparative example was zero, and no ethylene-methyl acrylate copolymer was synthesized.

[0147] The comparison of the copolymerization results of Example 11 and Comparative Example 1 is shown in Table 9.

[0148] Table 9 Copolymerization results of Example 11 and Comparative Example 1

[0149] Polymerization conditions: catalyst 30 μmol, activator MAO, Al / Ni=80:1, ethylene pressure 0.5 MPa, MA concentration 0.2 M, molar ratio of polar monomer to catalyst 266:1, temperature 50°C, polymerization time 1 h.

[0150] Compared to the examples, the β-diimine nickel catalyst Ni-0 showed no polymerization activity for the copolymerization of ethylene and MA. In contrast, the zwitterionic allyl nickel catalyst, due to the weak interaction between the sulfonate group and the metal center, effectively modulates and alters the electrophilicity of the metal center, significantly improving its tolerance to polar monomers. Consequently, it can effectively catalyze the copolymerization of ethylene and acrylate monomers.

[0151] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A zwitterionic allyl nickel complex having a structure shown in Formula I: In Formula I, R1 and R1' are the same or different and are independently selected from C1-C4 alkyl, C6-C 15 R2 is selected from H, C1-C6 alkyl.

2. The zwitterionic allyl nickel complex according to claim 1, wherein In formula I, R1 and R1' are the same or different and are independently selected from methyl, isopropyl and diphenylmethyl; R2 is selected from hydrogen and methyl.

3. The zwitterionic allyl nickel complex according to claim 2, wherein: In formula I, R1 and R1' are the same.

4. The zwitterionic allyl nickel complex according to claim 3, wherein In formula I, R1 and R1' are both methyl groups, and R2 is hydrogen; alternatively, R1 and R1' are both isopropyl groups, and R2 is hydrogen; alternatively, R1 and R1' are both benzhydryl groups, and R2 is methyl.

5. A method for preparing the zwitterionic allyl nickel complex according to any one of claims 1 to 4, comprising the following steps: The α-sulfonic acid-β-diimine lithium salt compound is mixed with an allyl nickel precursor to react to obtain the zwitterionic allyl nickel complex. The reaction process is as follows:

6. A catalyst system, comprising a main catalyst and an activator, wherein the main catalyst comprises the zwitterionic allyl nickel complex according to any one of claims 1 to 4.

7. The catalyst system according to claim 6, wherein The molar ratio of the main catalyst to the activator is 1:5-1:

100.

8. The catalyst system according to claim 6, wherein The activator comprises one or a combination of two or more of methylaluminoxane, modified methylaluminoxane, diethylaluminum monochloride, ethylaluminum dichloride, triisobutylaluminum, and tri(pentafluorophenyl)borane.

9. A copolymerization method of ethylene and acrylic ester, comprising the following steps: The zwitterionic allyl nickel complex described in any one of claims 1 to 4 or the catalyst system described in any one of claims 6 to 8 is used to catalyze the copolymerization reaction of ethylene and acrylate to obtain a branched ethylene-acrylate copolymer.

10. The copolymerization method according to claim 9, wherein The acrylic acid ester includes one or a combination of two or more of methyl acrylate, ethyl acrylate, butyl acrylate and tert-butyl acrylate.

11. The copolymerization method according to claim 9, wherein The polymerization temperature is 0°C-100°C.

12. The copolymerization method according to claim 9, wherein In the catalyst system, the molar ratio of the main catalyst to the acrylic ester is 1:266-1:1066.

13. The copolymerization method according to claim 9, wherein The pressure of ethylene is 0.1MPa-5.0MPa.

14. The copolymerization method according to claim 9, wherein The solvent used for the polymerization includes one or a combination of two or more of toluene, hexane, cyclohexane and heptane.

15. The ethylene-acrylate copolymer obtained by the copolymerization method according to any one of claims 9 to 14, wherein the degree of branching is 28 / 1000C-46 / 1000C and the melting temperature is 84.6°C-108.3°C.

16. The ethylene-acrylate copolymer according to claim 15, wherein The weight average molecular weight of the ethylene-acrylate copolymer is 1×10 5 g / mol-1×10 6 g / mol, and a molecular weight distribution of 1.31-2.33; in the ethylene-acrylate copolymer, the content of acrylate is 3.50mol%-8.99mol%, and the content of alkyl branches is 30 / 1000C-40 / 1000C; the melting temperature of the ethylene-acrylate copolymer is 84.6℃-98.3℃.

Images