Zwitterionic allyl nickel complex as well as preparation method and application thereof

Abstract

The invention provides a zwitterionic allyl nickel complex as well as a preparation method and application thereof. The zwitterionic allyl nickel complex has a structure as shown in a formula I: # imgabs0 #, in the formula I, R1 and R1'are the same or different and are respectively and independently selected from C1-C4 alkyl groups and C6-C15 aralkyl groups; and R2 is selected from H and C1-C6 alkyl groups. The zwitterionic allyl nickel complex catalyzes copolymerization of ethylene and an acrylate monomer, the reaction condition is mild, the catalytic activity is high, the molecular weight of the product is high, and a moderately branched ethylene-acrylate copolymer can be prepared.

Description

Technical Field

[0001] The invention belongs to the field of catalysts, and specifically relates to a new 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 copolymer (EMA) with an ester content of 10ω%-30ω% and a branched structure has good mechanical properties and compatibility and is widely used in many fields. In industry, EMA is obtained by 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 catalyzed olefins and polar monomers under mild conditions through coordination polymerization is a simple, direct and effective method.

[0003] Late transition metal catalysts, especially palladium catalysts, are widely used in the copolymerization of ethylene and polar monomers. It has been reported in the literature that α-diimine palladium catalyzes the copolymerization of ethylene and methyl acrylate (MA). Due to the rapid chain walking process, a highly branched copolymer with MA located at the end of the branch chain is usually prepared. EMA prepared by α-diimine palladium catalyst cannot be used as a thermoplastic resin due to its high degree of branching, no melting point, and poor mechanical properties. In addition, phosphine sulfonic acid palladium catalyzed the copolymerization of ethylene and MA to obtain a highly linear EMA with MA inserted into the main chain. Due to the lack of high-pressure free radical EMA side chains, the toughness and elasticity of the material are poor.

[0004] In addition, since palladium is a precious metal and is expensive, it is more practical to use a cheap and abundant nickel catalyst to catalyze the copolymerization of ethylene and polar monomers. However, due to the higher electrophilicity of the nickel metal center, it is usually difficult to catalyze the copolymerization of ethylene and MA to obtain high molecular weight copolymers. For example, α-diimine palladium can effectively catalyze the copolymerization of ethylene and methyl acrylate (MA), but the α-diimine nickel catalyst is not very effective in catalyzing the copolymerization of ethylene and methyl acrylate (MA). Therefore, it is of great significance to develop a nickel catalyst with weak electrophilicity and realize the copolymerization of ethylene and methyl acrylate (MA) through appropriate ligand design. The development of a nickel catalyst that can prepare EMA with a moderate degree of branching requires a comprehensive balance of the electrophilicity of the metal center so that it can copolymerize polar acrylate monomers; at the same time, chain walking can also occur, so that products with a structure similar to EMA obtained by free radical polymerization can be prepared. There is currently no literature report on this aspect, which has important industrial significance.

[0005] CN112538098A discloses an α-sulfonic acid-β-diimine nickel complex, a preparation method and its application as a catalyst in catalyzing 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 of catalytic copolymerization of olefins and polar monomers is 0℃-80℃, and the molar ratio of catalyst to polar monomer is 1:100-1:2000. With toluene as solvent and MAO as co-catalyst, the copolymerization activity of ethylene and methyl acrylate is 5.09×10 3 g / molNi·h, the weight average molecular weight of EMA is 41.9kg / mol, the molecular weight distribution is 1.39, the ester content in EMA is 0.8mol%, and the melting temperature is 98.5℃. This technology discloses a new catalyst that can be used for the copolymerization of ethylene and methyl acrylate, which is mainly used to prepare low-branched, semi-crystalline polyethylene. The alkyl coordinated with nickel is acetonitrile and halogen, and 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 halogen-substituted β-diimine titanium catalyst for ethylene copolymerization, and its structure is as follows:

[0008] Where R c is 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 The activity of ethylene and norbornene copolymerization was 3.9×10- 3 g / molTi·h, and the content of norbornene in the copolymer is 16.8%. The technology discloses a β-diimine titanium catalyst containing halogen substituents that can be used for the copolymerization of ethylene and norbornene. The alkyl coordinated with titanium is 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 anion in the catalyst is tetrakis(3,5-di(trifluoromethyl)phenyl)borate anion. It represents an allyl group connected to a nickel atom, n is an integer of 50-500, and has a free radical Br at the far end, and can be used for the polymerization of methyl methacrylate, methyl acrylate, acrylonitrile, acrylamide, styrene or N-vinyl pyrrolidone. The invention does not give copolymerization data.

[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 uses an α-diimine ligand with a specific structure, M is nickel, A is an allyl group or a benzyl group, wherein the allyl group is three adjacent sp2 carbon atoms bonded to the metal center in a π3 manner. These three sp carbon atoms can be replaced by other hydrocarbon groups or functional groups. Examples 200-203 give a method for synthesizing an allyl-coordinated diimine palladium catalyst, and Examples 497-515 give a method for preparing a diimine nickel catalyst containing an allyl substituent, but no experimental data for polymerization are published. This invention is an α-diimine nickel catalyst.

[0013] CN102105502A discloses a method for preparing a diblock copolymer of a monovinyl aromatic polymer block, wherein the repeating unit of A is selected from the residues of one or more aliphatic hydroxycarboxylic acids and the residues of one or more cyclic carbonates, the repeating unit of B is selected from the residues of monovinyl aromatic monomers, R and Y are derived from another functionalized alcohol that grows or grafts polyvinyl aromatic compounds in addition to the -OH functional group, and R is a connecting group. A bulky single-center 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 may be linked to form a ring, X is C 1-12 The catalyst can be used as a catalyst for preparing HAORYB diblock copolymers, and the patent discloses an embodiment of polylactic acid-polystyrene. The invention mainly protects the composition of the product and does not disclose the structural details of the catalyst.

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

[0016] The obtained polymer has C1 to C6 + Branched chain, and methyl group is the main one, accounting for 31.1%-98.6%. Under the conditions of 100℃-120℃, 6.9MPa, 18h, 0.0025mmol of catalyst, 160 equivalents of B(C6F5)3, 80 equivalents of NaBAF, 0.5mL of MA, and 9.5mL of chlorobenzene, ethylene and methyl acrylate were copolymerized with catalyst No. 45 to obtain 2.9g and 2.59g of polymers, respectively, with MA insertion rates of 0.53mol% and 0.45mol%, respectively, and weight-average molecular weights of 18706g / mol and 10394g / mol, respectively, and methyl branched chain accounts 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 copolymerization of ethylene and methyl acrylate, which can be used for copolymerization of ethylene and aryl olefinic acid ester or long-chain olefinic acid ester. The catalyst structure is as follows:

[0018]

[0019] CN1315573C discloses a β-diimine nickel catalyst dimer, the structure of which is as follows:

[0020] 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. With toluene as solvent and triethylaluminum as cocatalyst, the copolymerization activity of ethylene and methyl methacrylate is 6.6×10 4 g / molNi·h, the weight average molecular weight of EMMA is 150kg / mol, and the ester content in EMA is 0.7mol%. The catalyst can be used for copolymerization of ethylene and methyl methacrylate, and the molar ratio of the main catalyst to the co-catalyst is 1:10-1:40, but the copolymerization activity is not high.

[0021] CN113680389A discloses a multidentate β-diimine rare earth metal catalyst, the structure of which is as follows:

[0022] The catalyst is mainly used to prepare carbamate compounds or 2-oxazolidinone compounds. Carbamate compounds are important pesticide and drug intermediates. 2-Oxazolidinone compounds are important heterocyclic compounds that have attracted much attention in terms of antibacterial, anti-inflammatory, anti-cancer and anti-tuberculosis.

[0023] CN105646756B discloses an α-diimine nickel catalyst, the structure of which is as follows:

[0024] wherein Z and Y are C1-C4 alkyl groups, or Z and Y together with the carbon-carbon single bond connected together form an unsubstituted or substituted group selected from the group consisting of acenaphthenyl, phenanthrenyl, camphenyl and C5-C8 cycloalkyl groups; 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 4 The X coordinated with nickel can be allyl, halogen, C1-C4 alkyl, C2-C6 alkenyl or benzyl. The catalyst can catalyze the copolymerization of ethylene with long-chain alcohols, long-chain methoxy compounds, etc. to prepare high-end lubricating oil. 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 a preparation method and application thereof. The zwitterionic allyl nickel complex catalyzes the copolymerization of ethylene and acrylate monomers, has 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]

[0028] 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.

[0029] 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, benzhydryl; and R2 is selected from hydrogen and methyl.

[0030] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are the same.

[0031] 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 diphenylmethyl, and R2 is methyl.

[0032] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are both isopropyl, and R2 is hydrogen.

[0033] The present invention also provides a method for preparing the above-mentioned zwitterionic allyl nickel complex, which comprises the following steps:

[0034] α-sulfonic acid-β-diimide lithium salt compound and allyl nickel precursor Mix and react to obtain the zwitterionic allyl nickel complex, and the reaction process is as follows:

[0035]

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

[0037] (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;

[0038]

[0039] According to a specific embodiment of the present invention, the above preparation method comprises the following specific steps:

[0040] (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 lowering the temperature 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.

[0041] The present invention also provides a catalyst system, which comprises a main catalyst and an activator, wherein the main catalyst comprises the above-mentioned zwitterionic allyl nickel complex.

[0042] 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.

[0043] 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 tri(pentafluorophenyl)borane.

[0044] According to a specific embodiment of the present invention, preferably, the activator comprises methylaluminoxane (MAO) or a combination of tri(pentafluorophenyl)borane and triisobutylaluminum (TIBA).

[0045] 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.

[0046] 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.

[0047] According to a specific embodiment of the present invention, preferably, the acrylate includes methyl acrylate and / or ethyl acrylate.

[0048] According to a specific embodiment of the present invention, preferably, the polymerization temperature is 0°C-100°C, more preferably 30°C-80°C.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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 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°C-98.3°C.

[0054] The zwitterionic allyl nickel complex of the present invention overcomes the defects or deficiencies of the existing palladium catalysts being expensive, having low polymerization activity, and the existing nickel catalyst system being unable to prepare moderately branched ethylene-acrylate copolymers having excellent toughness and elasticity. The zwitterionic allyl nickel complex can be used as a main catalyst, and under the action of an activator, can catalyze the copolymerization of ethylene and acrylate monomers 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 and improve the performance of its copolymerized acrylate monomers due to the presence of a weak interaction between positive and negative ions. On the other hand, the nickel metal center still maintains a cationic center, can maintain a weak chain walking ability, and can 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 overall reaction conditions, high catalytic activity, and high product molecular weight, and has obvious technical advantages and industrial application prospects for preparing ethylene-acrylate copolymers by low-pressure coordination polymerization.

[0055] The present invention has the following beneficial effects:

[0056] 1. The zwitterionic allyl nickel complex provided by the present invention exists in the form of intramolecular cation and anion salts, and the metal center is an alkylated cationic active center capable of olefin coordination polymerization. The required amount of expensive activator is small, and industrial production has significant economic benefits;

[0057] 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 existence of a weak interaction between positive and negative ions, thereby significantly improving the copolymerization activity of catalyzing ethylene and acrylate monomers;

[0058] 3. The zwitterionic allyl nickel catalyst provided by the present invention has a nickel metal center that still maintains a cationic center, and thus has a weak chain walking ability, and can prepare a branched ethylene-acrylate copolymer similar to the high-pressure method, and has an industrial application prospect;

[0059] 4. The zwitterionic allyl nickel catalyst provided by the present invention for catalyzing the copolymerization of ethylene and acrylate has obvious technical advantages over industrial high-pressure free radical polymerization, such as mild reaction conditions, simple process equipment, and easier regulation of polymer structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A single crystal structure diagram of the zwitterionic allyl nickel complex provided in Example 8;

[0061] Figure 2 The H NMR spectrum of ethylene-methyl acrylate (EMA) provided in Example 11;

[0062] Figure 3 DSC analysis of ethylene methyl acrylate (EMA) provided for Example 11. DETAILED DESCRIPTION

[0063] In order to have a clearer understanding of the technical features, purposes 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 construed as limiting the applicable scope of the present invention.

[0064] The experimental methods in the following examples without specifying specific conditions are generally carried out according to conventional conditions in the art or according to conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets.

[0065] In order to clearly describe the compounds and complexes in the examples, the following are described:

[0066]

[0067] Formula III shows a β-diimine compound:

[0068] β-diimine compound A1, R1 and R1' are both methyl groups, and R2 is hydrogen;

[0069] β-diimine compound A2, R1 and R1' are both isopropyl, and R2 is hydrogen;

[0070] In the β-diimine compound A3, R1 and R1' are both diphenylmethyl and R2 is methyl.

[0071]

[0072] Formula II shows an α-sulfonic acid-β-diimine lithium salt compound:

[0073] α-sulfonic acid-β-diimide lithium salt compound L1, R1 and R1' are both methyl groups, and R2 is hydrogen;

[0074] α-sulfonic acid-β-diimide lithium salt compound L2, R1 and R1' are both isopropyl, and R2 is hydrogen;

[0075] In the α-sulfonic acid-β-diimine lithium salt compound L3, R1 and R1' are both diphenylmethyl, and R2 is methyl.

[0076]

[0077] Formula I shows a zwitterionic allyl nickel complex:

[0078] In the zwitterionic allyl nickel complex Ni-1, R1 and R1' are both methyl groups, and R2 is hydrogen;

[0079] In the zwitterionic allyl nickel complex Ni-2, R1 and R1' are both isopropyl, and R2 is hydrogen;

[0080] In the zwitterionic allyl nickel complex Ni-3, R1 and R1' are both diphenylmethyl, and R2 is methyl.

[0081] The synthesis route of the zwitterionic allyl nickel complex in the embodiment is as follows:

[0082]

[0083] 1. Preparation of ligands

[0084] Example 1

[0085] This embodiment provides a 2,6-dimethylphenyl substituted β-diimine compound A1, and its synthesis method is as follows:

[0086] 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) were added to a round-bottom flask in sequence; the system was heated to 100 ° C in an oil bath and reacted for 72 hours, then the solution was 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), washed and extracted twice with saturated NaHCO3 solution, the organic phase was collected, the organic phase was dried with anhydrous magnesium sulfate, filtered, and the filtrate was collected; then the filtrate was rotary evaporated to obtain a crude product, and the crude product was recrystallized with methanol to obtain a white solid. The yield is 87.5%. The H NMR spectrum is as follows: 1 HNMR(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).

[0087] Example 2

[0088] This embodiment provides a 2,6-diisopropylphenyl substituted β-diimine compound A2, the synthesis method of which is as follows:

[0089] 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 hours, then the solution was 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), washed and extracted twice with saturated NaHCO3 solution, the organic phase was collected, the organic phase was dried with anhydrous magnesium sulfate, filtered, and the filtrate was collected; then the filtrate was rotary evaporated to obtain a crude product, and the crude product was recrystallized with methanol to obtain a white solid. The yield is 86.2%. The H NMR spectrum is as follows: 1 HNMR(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).

[0090] Example 3

[0091] This embodiment provides a 2,6-benzhydryl 4-methylphenyl substituted β-diimine compound A3, the synthesis method of which is as follows:

[0092] 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) were added to a round-bottom flask in sequence; the system was heated to 120 ° C in an oil bath and reacted for 5 days. 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), washed and extracted twice with saturated NaHCO3 solution, the organic phase was collected, the organic phase was dried with anhydrous magnesium sulfate, filtered, and the filtrate was collected; the filtrate was then rotary evaporated to obtain a crude product, and the crude product was recrystallized with methanol to obtain 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).

[0093] Example 4

[0094] This embodiment provides an α-sulfonic acid-β-diimide lithium salt compound L1, and its synthesis method is as follows:

[0095] Under nitrogen atmosphere, β-diimine compound A1 (2.88 g, 9.24 mmol) was dissolved in dry tetrahydrofuran, and 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 heated to room temperature and stirred for 30 minutes; the temperature was lowered to -78°C, SO3.NMe3 (0.84 g, 6.04 mmol) was added, and the temperature was slowly raised to room temperature, and stirring was continued for 24 hours. The filtrate obtained after the solution was filtered was concentrated and frozen at -30°C to obtain a white precipitate, which was filtered to obtain a white solid, washed twice with n-hexane, and vacuum dried 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).

[0096] Example 5

[0097] This embodiment provides an α-sulfonic acid-β-diimide lithium salt compound L2, and its synthesis method is as follows:

[0098] According to the synthesis method of Example 4, β-diimine compound A1 was replaced by β-diimine compound A2 to obtain a white solid. The yield was 83.7%. The H NMR spectrum was 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).

[0099] Example 6

[0100] This embodiment provides an α-sulfonic acid-β-diimide lithium salt compound L3, and its synthesis method is as follows:

[0101] According to the synthesis method of Example 4, β-diimine compound A1 was replaced by β-diimine compound A3 to obtain a white solid. The yield was 72.8%. The H NMR spectrum was as follows: 1 H 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) .

[0102] 2. Preparation of zwitterionic allyl nickel complexes

[0103] Example 7

[0104] This embodiment provides a zwitterionic allyl nickel complex Ni-1, and its synthesis method is as follows:

[0105] Under nitrogen atmosphere, α-sulfonic acid-β-diimide lithium salt compound L1 (0.97 g, 1.77 mmol), allyl nickel chloride (II) dimer (0.53 g, 1.95 mmol) and dichloromethane (20 mL) were added to a Schlenk bottle with a branch in sequence, and the reaction was stirred at room temperature for 24 hours. The filtrate obtained by filtration was concentrated, and n-hexane was added to precipitate. The precipitate was filtered and washed twice with n-hexane, and vacuum dried to obtain a yellow powder. The yield was 81.3%. Elemental analysis (C 25 H 36 N2O3SNi, %) theoretical value: C, 59.66; H, 7.21; N, 5.57. Measured value: 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] + .

[0106] Example 8

[0107] This embodiment provides a zwitterionic allyl nickel complex Ni-2, and its synthesis method is as follows:

[0108] The α-sulfonic acid-β-diimide lithium salt compound L2 is reacted with allyl nickel chloride (II) dimer to obtain the product. The remaining specific steps are the same as those in Example 7, and the yield is 71.8%. The single crystal structure is shown in FIG. Figure 1 Elemental analysis (C 32 H 50 N2O3SNi, %) theoretical value: C, 64.39; H, 8.52; N, 4.55. Measured value: 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]+ .

[0109] Example 9

[0110] This embodiment provides a zwitterionic allyl nickel complex Ni-3, and its synthesis method is as follows:

[0111] 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. The yield was 68.8%. Elemental analysis (C 57 H 72 N2O3SNi, %) theoretical value: C, 79.01; H, 6.37; N, 2.46. Found value: 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] + .

[0112] 3. Copolymerization of ethylene and acrylate monomers

[0113] In the following examples, the catalytic activity is calculated by the final copolymer mass, the amount of metal nickel catalyst used and the polymerization time, the weight average molecular weight of the prepared polyolefin is measured by gel permeation chromatography, the melting point of the polymer is measured by differential scanning calorimetry, and the polar monomer insertion rate is calculated by nuclear magnetic hydrogen spectrum.

[0114] Example 10-37 provides a method for preparing ethylene-acrylate copolymer by copolymerization of ethylene and acrylate catalyzed by a nickel catalyst, and the specific reaction steps are as follows:

[0115] Heat the autoclave to 150℃ and evacuate for 2h. After cooling to room temperature under evacuation, replace ethylene three times. Add a certain amount of acrylate, a certain amount of activator and 30μmol of zwitterionic allyl nickel catalyst to the autoclave, and finally add dry toluene to keep the total volume at 40mL. After a certain pressure of ethylene is introduced, the polymerization reaction is carried out at a certain temperature for 4h. After the polymerization reaction reaches the set time, stop the introduction of ethylene, slowly release the pressure, open the autoclave, and terminate the reaction system with a 5% volume fraction of hydrochloric acid ethanol solution. The product is soaked in hydrochloric acid / ethanol, filtered, washed several times with anhydrous ethanol, and the polymer is placed in a 60℃ vacuum drying oven to dry to constant weight.

[0116] The H-NMR spectrum of the polymer sample was measured using a Bruker advance III 500MHz NMR spectrometer from Bruker Corporation, USA, at a temperature of 120°C. The deuterated reagent was deuterated o-dichlorobenzene (ο-C6D4Cl2), the test sample tube was a 5mm NMR tube, and tetramethylsilane (TMS) was used as an internal standard. The tilt angle was 74°, the delay time was 4s, the sampling time was 1.5s, and the determination method was proton decoupling method.

[0117] The branching degree of the polymer sample was calculated by high temperature hydrogen spectrum as follows:

[0118]

[0119] The insertion rate of methyl acrylate (MA) in the polymer is calculated using the following method:

[0120] 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:

[0121]

[0122] The molecular weight (Mw) and molecular weight distribution (PDI = Mw / Mn) of the polymer were determined using a high temperature gel chromatograph GPC PL-220. GPC PL-220 is equipped with two analytical columns (USA PLgel 10μm MIXED-B) and a differential refractive index detector (RI). GPC calibration curve: narrow distribution polystyrene (PS) is used as the standard sample. Sample test conditions: the solvent and mobile phase are 1,2,4-trichlorobenzene (0.125‰ antioxidant BHT has been added), at a test temperature of 150°C, the flow rate of the GPC mobile phase is 1.0mL / min, and the concentration of the polymer sample is 0.5mg / mL.

[0123] The melting temperature of the polymer was measured using a DSC-4000 differential scanning calorimeter from PerkinElmer. In a nitrogen atmosphere, the temperature was raised from -30°C to 200°C at a rate of 10°C / min, held constant for 3 minutes, then cooled to -30°C at a rate of 10°C / min, held constant for 3 minutes, and finally raised to 200°C at a rate of 10°C / min for a second heating. The melting point of the polymer was measured using a secondary heating curve.

[0124] Examples 10-12 provide the results of preparing EMA by copolymerization of ethylene and methyl acrylate catalyzed by different zwitterionic allyl nickel catalysts. Specific reaction conditions and polymerization results are shown in Table 1.

[0125] Table 1 Results of copolymerization of ethylene and methyl acrylate catalyzed by different nickel catalysts

[0126]

[0127]

[0128] 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.

[0129] 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.

[0130] Examples 13-16 provide the results of preparing EMA by catalyzing the copolymerization of ethylene and methyl acrylate 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.

[0131] The H NMR spectrum of ethylene-methyl acrylate (EMA) obtained in Example 11 is shown in Figure 2 , DSC analysis diagram as shown Figure 3 shown.

[0132] Table 2 Results of catalytic copolymerization of ethylene and methyl acrylate under different activators

[0133]

[0134] 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.

[0135] Examples 17-21 provide the results of preparing EMA by catalyzing the copolymerization of ethylene and methyl acrylate using a zwitterionic allyl nickel catalyst Ni-2 at different activator / Ni ratios. Specific reaction conditions and polymerization results are shown in Table 3.

[0136] Table 3 Results of catalytic copolymerization of ethylene and methyl acrylate under different activator ratios

[0137]

[0138] 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.

[0139] Examples 22 and 23 provide the results of preparing EMA by copolymerization of ethylene and methyl acrylate catalyzed by 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.

[0140] Table 4 Results of copolymerization of ethylene and methacrylic acid catalyzed by different MA concentrations

[0141]

[0142] 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.

[0143] Examples 24-27 provide the results of preparing EMA by catalyzing the copolymerization of 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.

[0144] Table 5 Results of catalytic copolymerization of ethylene and methacrylic acid at different temperatures

[0145]

[0146] 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.

[0147] Examples 28-31 provide the results of preparing EMA by copolymerization of ethylene and methyl acrylate using a zwitterionic allyl nickel catalyst Ni-2 under different ethylene pressures. Specific reaction conditions and polymerization results are shown in Table 6.

[0148] Table 6 Results of catalytic copolymerization of ethylene and methacrylic acid under different ethylene pressures

[0149]

[0150] 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.

[0151] Examples 32 and 33 provide the results of preparing EMA by catalyzing the copolymerization of ethylene and methyl acrylate in different solvents using a zwitterionic allyl nickel catalyst Ni-2. The specific reaction conditions and polymerization results are shown in Table 7.

[0152] Table 7 Results of catalytic copolymerization of ethylene and methacrylic acid under different solvents

[0153]

[0154] 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.

[0155] Examples 34-36 provide the results of copolymerization of ethylene and different types of acrylate monomers catalyzed by a zwitterionic allyl nickel catalyst Ni-2. Specific reaction conditions and polymerization results are shown in Table 8.

[0156] Table 8 Results of copolymerization of ethylene with different acrylate monomers

[0157]

[0158]

[0159] 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.

[0160] In order to more clearly demonstrate the beneficial effects of the catalyst of the present invention, a β-diimine nickel catalyst (Ni-0) with a similar structure 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:

[0161] The synthesis method is as follows:

[0162] (1) Preparation of β-diimine compound The same as 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, then the solution was cooled to room temperature and the solvent was removed by rotary evaporation to obtain a brown solid, which was dissolved in dichloromethane (300 mL), washed and extracted twice with saturated NaHCO3 solution, the organic phase was collected, the organic phase was dried with anhydrous magnesium sulfate, filtered, and the filtrate was collected; then the filtrate was rotary evaporated to obtain a crude product, which was recrystallized with methanol to obtain 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);

[0163] (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 in sequence to a Schlenk flask with a branch under nitrogen atmosphere. The reaction was stirred at room temperature for 24 h. The filtrate was filtered and concentrated. n-hexane was added to precipitate, which was filtered and washed twice with n-hexane. The precipitate was dried in vacuo to obtain the target product.

[0164] Comparative Example 1

[0165] In this comparative example, 30 μmol of β-diimine nickel catalyst Ni-0 was used instead of zwitterionic allyl nickel catalyst Ni-2 to copolymerize ethylene monomer and methyl acrylate, and the polymerization method was the same as the copolymerization reaction of ethylene and methyl acrylate in the aforementioned Example 11. No solid polymer was obtained in this polymerization. In this comparative example, the copolymerization activity of β-diimine nickel was zero, and no ethylene-methyl acrylate copolymer was synthesized.

[0166] The copolymerization results of Example 11 and Comparative Example 1 are compared in detail in Table 9.

[0167] Table 9 Copolymerization results of Example 11 and Comparative Example 1

[0168]

[0169] 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.

[0170] Compared with the examples, the β-diimine nickel catalyst Ni-0 has no polymerization activity for the copolymerization of ethylene and MA. Compared with this, the zwitterionic allyl nickel catalyst has a weak interaction between the sulfonate group and the metal center, the electrophilicity of the metal center is effectively regulated and changed, and the tolerance to polar monomers is significantly improved, so it can effectively catalyze the copolymerization of ethylene and acrylate monomers.

[0171] 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 protection scope 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℃.

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