Preparation method of nickel catalyst containing rigid triphenylmethyl groups and its application in olefin polymerization

Abstract

This invention introduces a series of nickel diimine catalysts equipped with distally rigid triphenylmethyl groups. By introducing functional groups with different electronic effects and steric hindrances, precise control over catalyst performance is achieved. These meticulously designed catalysts not only exhibit excellent activity and outstanding thermal stability, but also efficiently catalyze ethylene polymerization to produce polyethylene elastomers with adjustable parameters such as molecular weight, branch density, and melting point. Furthermore, they possess the unique ability to catalyze the copolymerization of ethylene with polar monomers. The advent of this series of innovative catalysts opens up a completely new path for the development of polyolefin elastomers, providing valuable alternatives.

Description

Technical Field

[0001] This invention belongs to the field of polyolefin metal catalysts, specifically relating to a method for preparing a nickel catalyst with long-distance rigid steric hindrance and its application in preparing ethylene / polar monomer copolymers. Background Technology

[0002] Since Brookhart discovered α-diimide catalysts in the 1990s, these catalysts have received considerable attention in the field of olefin polymerization (Johnson J, Killian C, Brookhart M. New Pd(II) and Ni(II) based catalysts for polymerization of ethylene and α-olefins. J. Am. Chem. Soc. 1995, 117(23): 6414–6415). Their unique chain-walking mechanism endows polyethylene with tunable topology, melting point, and molecular weight. However, the classic α-diimide system also suffers from low thermal stability, easily decomposing and deactivating at high temperatures, resulting in a significant reduction in molecular weight. Therefore, a large amount of research has focused on improving the thermal stability of α-diimine catalysts (Sui, X.; Hong, C.; Pang, W.; Chen, C. Unsymmetrical α-Diimine Palladium Catalysts and Their Properties in Olefin (Co) Polymerization. Mater. Chem. Front. 2017, 1(5), 967-972). The steric hindrance and electronic effects of α-diimine ligands are two key factors affecting catalyst performance. The presence of a large substituent at the ortho position of aniline can effectively block the axial position of the metal center, inhibit chain transfer, thereby improving thermal stability and obtaining a polymer with high molecular weight and low branch density (Turney, KM; Kaewdeewong, P.; Eagan, JMEthylenePolymerization Using Heterogeneous Multinuclear Nickel Catalysts Supported by a Crosslinked Alpha Diimine Ligand Network[J].Polym.Chem.2023,14(16),1983-1990).

[0003] This strategy has been widely applied in the design of α-diimine catalysts. For example, Brookhart and Daugulis et al. replaced the α-diimine ligand with a bulkier 8-p-methylnaphthalene to synthesize a nickel catalyst, which, compared to the classic α-diimine nickel catalyst, has a larger axial volume, resulting in a higher polyethylene molecular weight (up to 178.1 × 10⁻⁶). 4 g mol -1 Long et al. introduced diisopropylphenyl into α-diimine ligands, increasing the axial steric hindrance of nickel catalysts and significantly improving their high thermal stability and polymerization activity. The introduction of the diisopropyl substituent provided important progress for the development of later transition metal catalysts, leading to the design and synthesis of a series of sterically hindered α-diimine nickel and palladium catalysts. Subsequently, Chen reported a series of α-diimine Pd complexes with electron-donating and electron-withdrawing substituents, synthesizing polyethylene with high molecular weight, extremely low branching density, and unique microstructure. Chen also reported the synthesis of α-diimine Pd complexes containing bulky 2-tert-butylphenyl, further modulating the polymer topology through electronic effects, and using these complexes to copolymerize ethylene with polar monomers to prepare high-performance thermoplastic elastomers. In summary, following the discovery of the significant impact of diisopropyl substituents, research on the further design of transition metal catalyst ligands based on them continues to flourish (Liu, YS; Harth, E. Distorted Sandwich α-Diimine PdIICatalyst: Linear Polyethylene and Synthesis of Ethylene / Acrylate Elastomers. Angew. Chem. Int. Ed. 2021, 60(45), 24107-24115; Wang, C.; Tang, SZ; He, Y. Preparation of polyethylene elastomers with increased highmolecular weight and nearly perfect strain recovery by steric control of asymmetric α-diimine nickel catalyst. Inorg. Chim. Acta. 2024, 569).

[0004] Based on the interesting substituent structure of diisopropyl, further adjustment of the ligand structure of nickel catalysts is expected to improve the performance of nickel-catalyzed ethylene polymerization. In particular, using ethylene as a single raw material, a series of diimine nickel catalysts were used to synthesize polyethylene elastomers with excellent elastic properties. Further adjustment of the ligand structure of diimine nickel catalysts can give polyolefin elastomers better mechanical properties and elastic recovery rate (Bi,ZX; Zhou,JJ; Zhu,NN Heterogeneous Nickel Catalysts for the Synthesis of Ethylene-Based Polyolefin Elastomers[J]. Macromolecules 2024,57,1080-1086).

[0005] In this invention, we attach a triphenylmethyl group at the para-position of the α-diimine nickel catalyst to form a distal rigid steric hindrance, which, together with the group near the metal center, forms a large steric hindrance to regulate the polymerization performance of the nickel catalyst. Furthermore, we design different diisopropyl substituents to further precisely regulate the polymerization activity of the nickel catalyst, the molecular weight of polyethylene, and the branching density. These nickel catalysts have also been used to prepare polyolefin elastomers with excellent mechanical and elastic properties, and have enabled the copolymerization of ethylene with a series of polar monomers. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to solve the problem of poor thermal stability of existing α-diimine nickel catalysts. The main purpose is to introduce rigid triphenylmethyl groups into the diimine nickel catalyst, which greatly improves the electrophilicity of the nickel metal center through electronic and steric effects, improves the chain walking polymerization behavior, and thus improves the thermal stability and catalytic ability of nickel catalysts to polymerize ethylene.

[0007] The specific technical solution of this invention is as follows:

[0008] An α-diimine nickel catalyst with a rigid steric hindrance at the distal end formed by triphenylmethyl groups has the following structural formula:

[0009]

[0010] In formula A above, R1 is hydrogen-based, methyl, ethyl, isopropyl, phenyl, diphenylmethyl, 4,4'-difluorodiphenylmethyl, or 4,4'-di-tert-butyldiphenylmethyl; R2 is an alkane.

[0011] This invention also provides a method for preparing an α-diimine nickel catalyst with the above-described structure and rigid steric hindrance at the distal end formed by triphenylmethyl groups. The catalyst is obtained by reacting a diimine ligand with 1.5 equivalents of (DME)NiBr2 in an organic solvent at room temperature. After the reaction, the organic solvent is filtered, concentrated under reduced pressure, and then hexane is added to precipitate the product. After complete precipitation, the product is filtered, washed, and dried to obtain the α-diimine nickel catalyst with rigid steric hindrance at the distal end formed by triphenylmethyl groups.

[0012] Furthermore, the structure of the diimine ligand with distal rigid steric hindrance formed by triphenylmethyl is shown below, where R1 is hydrogen-based, methyl, ethyl, isopropyl, diphenylmethyl, phenyl, 4,4'-difluorodiphenylmethyl, or 4,4'-di-tert-butyldiphenylmethyl; and R2 is an alkane.

[0013]

[0014] Furthermore, the diimine ligand can be synthesized using methods disclosed in the prior art, specifically referring to the method in the literature (Menglong G, Shizhen D, Qing B. Ethylene polymerization by 2,3-diiminobutylnickel bromide pre-catalysts bearing remote benzhydryl substituents. J. Organomet. Chem. 2015, 798: 401–407).

[0015] Furthermore, the present invention also provides a method for preparing the tetraphenylamine involved, wherein aniline and triphenylmethyl chloride in a molar ratio of 10:1 are reacted at 220°C for 10 min, the reactants are cooled to room temperature, an appropriate amount of methanol and hydrochloric acid solution is added, and the reactants are then heated under reflux for 10 min. After cooling, the precipitate is filtered, washed, and dried to obtain tetraphenylamine.

[0016] This invention is based on the high catalytic performance of α-diimine nickel catalysts with rigid steric hindrance at the distal end formed by triphenylmethyl groups in olefin polymerization reactions. Therefore, its application as a catalyst for olefin polymerization reactions is also within the scope of protection of this invention. When used as a catalyst, it can catalyze the homopolymerization of ethylene, and it can also catalyze the copolymerization of ethylene with polar monomers, such as the copolymerization of ethylene with undecenoic acid methyl ester. The polar monomers refer to monoolefins containing heteroatoms, with the double bonds at the ends of the molecular chains.

[0017] Furthermore, in the olefin polymerization reaction, using an α-diimine nickel catalyst with rigid steric hindrance at the distal end formed by triphenylmethyl groups and an alkyl aluminum chloride as a co-catalyst, the monomers undergo polymerization under the combined action of these substances.

[0018] Furthermore, the alkyl aluminum chloride is diethyl aluminum chloride (Et2AlCl) or ethyl aluminum dichloride (EtAlCl2), preferably diethyl aluminum chloride.

[0019] Furthermore, the molar ratio of aluminum in the co-catalyst to nickel in the catalyst is 100-5000:1. This molar ratio affects the molecular weight and molecular weight distribution of the resulting polymer, and is preferably 500:1.

[0020] Furthermore, olefin polymerization can be carried out in any solvent that does not adversely affect the catalyst system, such as toluene, xylene, and alkane solvents; organic solvents have no significant impact on product performance. During polymerization, the pressure of the monomer ethylene and the concentration of polar monomers can be adjusted as needed.

[0021] Furthermore, the olefin polymerization reaction includes the following steps: adding the polymerization monomer and organic solvent into a reaction vessel, adding a catalyst and a co-catalyst, controlling the reaction temperature to carry out the reaction, and washing and drying the obtained polymer after the reaction to obtain polyolefin.

[0022] Furthermore, the reaction temperature is 0℃-200℃, and the reaction temperature affects the molecular weight and other properties of the product. It is preferably 30℃-120℃, and the reaction time is generally 10-60 min depending on the monomer.

[0023] Furthermore, during the homopolymerization reaction of ethylene, the monomer for polymerization is ethylene, which is introduced into the reactor. The pressure of ethylene in the reactor is 0-20 atmospheres, which affects the molecular weight and branching degree of the product, and is preferably 8 atmospheres. During the copolymerization reaction, the monomers for polymerization are ethylene and a polar monomer. The pressure of ethylene in the reactor is 0-20 atmospheres, preferably 8 atmospheres. The concentration of other monomers (methyl undecenoate) in the organic solvent is 0.1-5 mol / L, preferably 0.1-2 mol / L.

[0024] Furthermore, the reaction is carried out under anhydrous and oxygen-free conditions. Attached Figure Description

[0025] Figure 1 Catalyst single crystal of Example 4;

[0026] Figure 2 Catalyst single crystal of Example 5;

[0027] Figure 3 The 1H NMR spectrum of the ligand (L4) in Example 4 of this invention;

[0028] Figure 4 The carbon NMR spectrum of the ligand (L4) in Example 4 of this invention;

[0029] Figure 5 The 1H NMR spectrum of the ligand (L5) in Example 5 of this invention;

[0030] Figure 6 The NMR fluorine spectrum of the ligand (L5) in Example 5 of this invention;

[0031] Figure 7 The carbon NMR spectrum of the ligand (L5) in Example 5 of this invention; Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0034] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0035] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0036] In the following examples, the ligands used were synthesized according to the method described in the literature (Menglong G, Shizhen D, Qing B. Ethylene polymerization by 2,3-diiminobutylnickel bromide pre-catalysts bearing remote benzhydryl substituents. J. Organomet. Chem. 2015, 798:401–407). The steps were as follows: Acenathoine, ZnCl2, and a certain amount of glacial acetic acid solution were added to a round-bottom flask and heated to reflux until all the acenathoine was dissolved. After slight cooling, aniline containing different substituents was added to the flask, and the mixture was heated to reflux for several hours. After cooling to room temperature, the mixture was filtered through a Buchner funnel. The filter cake was washed 2-3 times with diethyl ether, dissolved in CH2Cl2, and then a saturated potassium oxalate solution was added. After the reaction was complete, the organic phase was separated, concentrated, and recrystallized to obtain the ligands.

[0037] Example 1

[0038] Preparation method of α-diimine nickel complex (Ni1) containing 4-triphenylmethyl:

[0039]

[0040]

[0041] Step 1: Add 1 eq. of triphenylchloromethane and 11 eq. of 2,4-dimethylaniline to the same round-bottom flask and reflux at 220°C for 30 min. Then cool the reactants to room temperature, add 2 eq. of 2M hydrochloric acid and an equal volume of methanol solvent under vigorous stirring, reflux at 120°C for 10 min, cool to room temperature, filter, and the filter cake is the product. Wash the filter cake with water (3 × 20 mL) and dry to obtain aniline (80% yield). 1 H NMR (400MHz, CDCl3): δ7.22 (d, J = 4.2Hz, 13H), 7.15 (q, J = 4.5Hz, 3H), 6.75 (s, 2H), 3.49 (s, 2H, -NH2), 2.06 (s, 6H, -CH3). 13 C NMR (101MHz, CDCl3): δ147.48,140.48,136.16,131.24,131.19,127.32,125.64,120.57,64.33,18.03.

[0042]

[0043] Step 2: Add 2.5 eq. of aniline, 1 eq. of acenaphthene, and 1.2 eq. of zinc chloride to the same round-bottom flask, then add an appropriate amount of acetic acid, and reflux at 160°C for 10 h. After the reaction is complete, cool to room temperature, filter, wash the filter cake twice with acetic acid, and then wash the filter cake two to three times with anhydrous diethyl ether. Dissolve the filter cake in dichloromethane, add excess saturated potassium oxalate aqueous solution, stir for 3 h, extract the organic phase three times with water, dry the organic phase, evaporate excess solvent, and recrystallize from anhydrous methanol to obtain ligand L1 (90% yield). 1 H NMR (400MHz, CDCl3): δ7.79(d,J=8.2Hz,2H),7.28(s,4H),7.22(t,J=7.6Hz,14H),7.18 –7.09(m,10H),7.04(d,J=2.6Hz,2H),6.92(s,3H),6.50(d,J=7.1Hz,2H),1.93(s,12H). 13C NMR (101MHz, CDCl3): δ161.15,147.23,142.18,140.53,131.45,131.31,131.23,129.62 ,128.91,128.10,127.45,127.16,125.87,123.87,122.58,64.77,18.13.Anal.Calc.for C 66 H 52 N2:C,90.79;H,6.00;N,3.21, Found:C,90.81;H,6.04;N,3.18.

[0044]

[0045] Step 3: Dissolve 1 eq. of the ligand and 2.5 eq. of (DME)NiBr2 in dry CH2Cl2 and react overnight. Filter with dry diatomaceous earth, collect the organic phase, remove excess solvent under anhydrous and oxygen-free conditions, recrystallize with dry n-hexane, wash the product with diethyl ether (4 × 5 mL), and dry under vacuum to obtain an orange-red or brownish-red solid, which is the nickel complex Ni1 (85% yield). Anal.Calc.for C 66 H 52 Br2N2Ni:C,72.62;H,4.80;N,2.57.Found:C,71.25;H,4.56;N,2.75.

[0046] Example 2

[0047] Preparation method of α-diimine nickel complex (Ni2) containing 4-triphenylmethyl:

[0048]

[0049] Step 1: The preparation method is the same as in Example 1, except that the reactant aniline is replaced with 2,4-diethylaniline, and the product (65% yield) is obtained. 1 H NMR (400MHz, CDCl3): δ7.22(d,J=6.2Hz,13H),7.17–7.11(m,3H),6.77(s,2H) ,3.56(s,2H,-NH2),2.42(q,J=7.5Hz,4H,-CH2),1.09(t,J=7.5Hz,6H,-CH3). 13CNMR (101MHz, CDCl3): δ147.56,139.20,136.42,131.24,129.22,127.28,126.62,125.62,64.57,24.56,13.28. Elemental Analysis: C, 88.96; H, 7.47; N, 3.58.

[0050]

[0051] Step 2: The preparation method is the same as in Example 1, with ligand L2 (70% yield). 1 H NMR (400MHz, CDCl3) δ7.87(d,J=8.3Hz,2H),7.37(d,J=7.9Hz,14H),7.32(t,J=7.6Hz,17H),7.23(d,J=7.2Hz,7H),7.12(d,J=6. 0Hz, 3H), 7.05 (s, 4H), 6.57 (d, J = 7.2Hz, 2H), 2.46 (dq, J = 15.0, 7.6Hz, 4H), 2.32 (dq, J = 14.9, 7.5Hz, 4H), 0.96 (t, J = 7.5Hz, 12H). 13 C NMR (101MHz, CDCl3): δ161.01,147.30,146.64,142.36,140.62,131.27,129.83,129.71, 129.66,128.76,127.93,127.41,127.10,125.83,123.00,64.98,24.95,14.06.Elemental Analysis:C,90.48;H,6.51;N,3.01.

[0052]

[0053] Step 3: The preparation method is the same as in Example 1. The final product, an orange-red or brownish-red solid, is the nickel complex Ni2 (86% yield). Anal.Calc.for C 70 H 60 Br2N2Ni:C,73.25;H,5.27;N,2.44, Found:C,75.23;H,4.28;N,2.58.

[0054] Example 3

[0055] Preparation method of α-diimine nickel complex (Ni3) containing 4-triphenylmethyl groups:

[0056]

[0057]

[0058] Step 1: The preparation method is the same as in Example 1, except that the reactant aniline is replaced with 2,4-diisopropylaniline, and the product (50% yield) is obtained. 1 H NMR (400MHz, CDCl3): δ7.26–7.18(m,13H),7.14(dq,J=5.9,2.6Hz,3H),6.83(d,J=1.5Hz, 2H), 3.63 (s, 2H, -NH2), 2.85 (hept, J=6.9Hz, 2H, -CH), 1.09 (dd, J=6.8, 1.6Hz, 12H, -CH3). 13 C NMR (101MHz, CDCl3): δ 147.60, 137.74, 136.48, 131.24, 127.29, 127.22, 126.11, 125.62, 64.85, 28.03, 22.53. Elemental Analysis: C, 88.73; H, 7.93; N, 3.34.

[0059]

[0060] Step 2: The preparation method is the same as in Example 1, with ligand L3 (50% yield). 1 H NMR (400MHz, CDCl3) δ7.84(d,J=8.2Hz,2H),7.36(d,J=7.9Hz,12H),7.30(t,J=7.5Hz,13H),7.25–7.18(m,8H ),7.10(s,4H),6.45(d,J=7.2Hz,2H),2.91(p,J=6.9Hz,4H),1.07(d,J=6.8Hz,12H),0.72(d,J=6.8Hz,12H). 13 C NMR (101MHz, CDCl3) δ161.32,147.36,145.37,142.55,140.77,134.31,131.21,131.06,129. 55,128.78,127.67,127.39,126.85,125.81,123.40,65.28,28.64,23.25,23.16.Elemental Analysis:C,90.20;H,6.96;N,2.84.

[0061]

[0062] Step 3: The preparation method is the same as in Example 1. The final product, an orange-red or brownish-red solid, is the nickel complex Ni3 (86% yield). Anal.Calc.for C 74 H 68 Br2N2Ni:C,73.83;H,5.69;N,2.33, Found:C,74.56;H,5.12;N,2.92.

[0063] Example 4

[0064] Preparation method of α-diimine nickel complex (Ni4) containing 4-triphenylmethyl:

[0065]

[0066] Step 1: Add 1 eq. of triphenylmethylaniline and 2.1 eq. of diphenylmethanol to the same pressure-resistant flask, heat to 160°C to melt the reactants, then dissolve 0.5 eq. of zinc chloride in an appropriate amount of hydrochloric acid solution and add it to the pressure-resistant flask. React for 1 h. Cool the reactants to room temperature, extract three times with dichloromethane and water, collect the organic phase, dry it with anhydrous sodium sulfate, evaporate excess solvent, and recrystallize from anhydrous methanol to obtain aniline (80% yield). 1 H NMR (400MHz, CDCl3): δ7.25–7.10(m,14H),7.10–6.99(m,10H),6.96–6.90(m,13H),6.41(s,2H,-CH),3.36(s,2H,-NH2). 13 C NMR (101MHz, CDCl3): δ147.20,142.62,139.64,135.86,132.00,130.83,129.27,128.38,127.99,127.10,126.43,125.33,64.33,52.23.Elemental Analysis:C,91.72;H,6.19;N,2.10.

[0067]

[0068] Step 2: The preparation method is the same as in Example 1, with ligand L4 (82% yield). 1 H NMR (400MHz, CDCl3): δ7.44 (d, J=8.4Hz, 2H), 7.22–7.02 (m, 48H), 7.00–6.90 (m, 9H) ,6.71(t,J=7.7Hz,2H),6.63–6.41(m,20H),5.79(d,J=7.1Hz,2H),5.64(s,4H,-CH). 13C NMR (101MHz, CDCl3): δ163.89,147.01,146.75,144.13,142.32,142.11,132.14,131.15,130.79,129.67,129.53,129. 36,129.25,128.44,128.05,127.99,127.68,127.57,126.54,125.90,125.61,125.54,124.41,65.00,51.44.Elemental Analysis:C,92.39;H,5.72;N,1.89.

[0069]

[0070] Step 3: The preparation method is the same as in Example 1. The final product is an orange-red or brownish-red solid, which is the nickel complex Ni4 (80% yield). Its single-crystal structure is shown in Figure 1. (Anal.Calc.for C) 114 H 84 Br2N2Ni:C,80.52;H,4.98;N,1.65, Found:C,81.54;H,4.28;N,1.78.

[0071]

[0072]

[0073] Example 5

[0074] Preparation method of α-diimine nickel complex (Ni5) containing 4-triphenylmethyl:

[0075]

[0076] Step 1: The preparation method is the same as in Example 4, except that the reactant aniline is replaced with 4,4'-difluorodiphenylmethanol, and the product (54% yield) is obtained. 1 H NMR (400MHz, CDCl3): δ7.12–7.05(m,10H),6.95–6.89(m,8H),6.88–6.82(m,18H),6.32(d,J=2.6Hz,2H,-CH),3.32(s,2H,-NH2). 19 F NMR (376MHz, CDCl3): δ-116.08. 13C NMR (101MHz, CDCl3): δ162.86,160.42,146.94,139.31,138.06,138.03,136.39,132.02,1 30.84,130.60,130.52,127.82,127.21,125.63,115.53,115.32,64.34,50.67.Elemental Analysis:C,82.80;H,5.10;N,1.90.

[0077]

[0078] Step 2: The preparation method is the same as in Example 1, with ligand L5 (70% yield). 1 H NMR (400MHz, CDCl3): δ7.62 (d, J=8.2Hz, 2H), 7.21–7.10 (m, 31H), 6.93 (s, 4H), 6.87–6.7 7(m,19H),6.48–6.41(m,8H),6.21–6.12(m,8H),5.77(d,J=7.1Hz,2H),5.49(s,4H,-CH). 19 F NMR (376MHz, CDCl3): δ-116.66,-116.96. 13 C NMR (101MHz, CDCl3): δ163.75,162.55,161.95,160.12,159.51,146.53,146.22,142.92,139.69,139.29,137.61,137.58,132.07,130.85,130. 66,130.60,130.39,130.31,129.51,128.84,127.84,127.57,126.53,12 5.83,124.11,115.05,114.84,114.73,114.51,64.88,49.88.Elemental Analysis:C,84.43;H,4.65;N,1.73.

[0079]

[0080] Step 3: The preparation method is the same as in Example 1. The final product is an orange-red or brownish-red solid, which is the nickel complex Ni5 (84% yield). Its single-crystal structure is shown in Figure 2. (Anal.Calc.for C) 114 H 76Br2F8N2Ni:C,74.24;H,4.15;N,1.52, Found:C,75.15;H,4.28;N,1.45.

[0081]

[0082]

[0083] Example 6

[0084] Preparation method of α-diimine nickel complex (Ni6) containing 4-triphenylmethyl groups:

[0085]

[0086] Step 1: The preparation method is the same as in Example 4, except that the reactant aniline is replaced with 4,4'-di-tert-butyldiphenylmethanol, and the product (30% yield) is obtained. 1 H NMR (400MHz, CDCl3): δ7.19(d,J=8.0Hz,8H),7.09(d,J=6.7Hz,9H),6.99(dd,J=7.6,2.3 Hz,6H),6.88(d,J=8.0Hz,8H),6.47(s,2H,-CH),3.40(s,2H,-NH2),1.29(s,36H,-CH3). 13 C NMR (101MHz, CDCl3): δ148.82,147.34,139.73,139.70,135.64,131.61,130.83, 128.88,128.48,127.05,125.21,125.11,64.40,51.27,34.34,31.43.Elemental Analysis:C,90.18;H,8.25;N,1.57.

[0087]

[0088] Step 2: The preparation method is the same as in Example 1, with ligand L6 (45% yield). 1 H NMR (400MHz, CDCl3): δ7.40(d,J=8.2Hz,2H),7.25–7.12(m,29H),7.12–7.06(m,8H),7.04(s,4H),6.90(d,J=8.0Hz,8H),6.7 2(t,J=7.8Hz,2H),6.56(s,15H),5.83(d,J=7.2Hz,2H),5.59(s,4H,-CH),1.26(s,36H,-C(CH3)3),0.95(s,36H,-C(CH3)3).13 C NMR (101MHz, CDCl3): δ163.63,148.09,147.74,147.16,146.72,141.71,140.92,139.79,131.84,131.38,130.87,129.23 ,128.91,128.58,127.95,127.49,126.54,125.48,124.78,124.39,65.04,50.43,34.31,33.94,31.50,31.18.Elemental Analysis:C,90.83;H,7.70;N,1.47.

[0089]

[0090] Step 3: The preparation method is the same as in Example 1. The final product, an orange-red or brownish-red solid, is the nickel complex Ni5 (86% yield). Anal.Calc.for C 146 H 148 Br2N2Ni:C,81.59;H,6.94;N,1.30, Found:C,80.59;H,7.01;N,1.39.

[0091] Example 7

[0092] Ethylene polymerization was carried out using the catalysts prepared in Examples 4-6, and the specific polymerization methods are as follows:

[0093] In a glove box under a nitrogen atmosphere, 30 mL of toluene was added to a 300 mL autoclave (equipped with a stirrer, heating device, and thermometer). The container was then connected to a high-pressure pipeline, and the pipeline was evacuated. The container temperature was set to the desired temperature and maintained for 5 minutes. 0.5 mL of diethylaluminum chloride (2 mol / L) was injected into the autoclave using a syringe. Then, 1.0 μmol of the catalyst prepared in Examples 4-6 was dissolved in 1.0 mL of dichloromethane and injected into the autoclave using a syringe. The ethylene valve was then opened, and ethylene was introduced into the autoclave. The ethylene pressure was adjusted to 8 atm, and the reaction was allowed to proceed for 10 minutes. The reaction was then stopped, the autoclave was opened, and ethanol was added to precipitate the solid. The mixture was filtered under reduced pressure and dried in a vacuum drying oven to obtain a white solid.

[0094] The results of ethylene polymerization catalyzed by the catalysts prepared in Examples 4-6 are shown in Table 1 below:

[0095] Table 1 Effect of temperature on ethylene polymerization

[0096]

[0097] Note: The co-catalyst used is diethylaluminum chloride, the catalyst dosage is 1.0 μmol, Ni / Al = 1:500; the catalytic activity unit is kg polyethylene / mol catalyst·h; B is the degree of branching of the polymer, the unit is B / 1000C.

[0098] Example 8

[0099] The catalysts prepared in Examples 4-6 were used to copolymerize ethylene with UCOOME, and the specific polymerization methods are as follows:

[0100] In a glove box under a nitrogen atmosphere, a polar monomer solution using toluene as a solvent was added to a 300 mL autoclave (equipped with a stirrer, heating device, and thermometer). The container was then connected to a high-pressure pipeline, and the pipeline was evacuated. The container temperature was set to the desired temperature and maintained for 5 minutes. 5.0 mL of diethylaluminum chloride (2 mol / L) was injected into the autoclave using a syringe. Then, 5.0 μmol of the catalyst prepared in Examples 4-6 was dissolved in 1.0 mL of dichloromethane and injected into the autoclave using a syringe. The ethylene valve was then opened, and ethylene was introduced into the autoclave. The ethylene pressure was adjusted to 8 atm, and the reaction was allowed to proceed for 10 minutes. The reaction was then stopped, the autoclave was opened, and ethanol was added to precipitate the solid. The solid was filtered under reduced pressure and dried in a vacuum drying oven to obtain a white solid.

[0101] The results of copolymerization of ethylene and UCOOMe using the catalysts prepared in Examples 4-6 are shown in Table 1 below:

[0102] Table 2 Nickel catalysts for copolymerization of ethylene and UCOOMe

[0103]

[0104] Note: The co-catalyst used was diethylaluminum chloride, with a catalyst dosage of 5.0 μmol and a Ni / Al ratio of 1:1000; the catalytic activity unit is kg polyethylene / mol catalyst·h; X is the insertion rate of the polar monomer.

[0105] In summary, this invention presents a series of nickel diimine catalysts equipped with distally rigid triphenylmethyl groups. By introducing functional groups with different electronic effects and steric hindrances, precise control over the performance of nickel catalysts is achieved. Under the same polymerization conditions, compared to catalysts Ni1-Ni3 in Examples 1-3, catalysts Ni4-Ni6 in Examples 4-6 not only exhibit superior activity and excellent thermal stability, but also efficiently catalyze ethylene polymerization, producing polyethylene elastomers with adjustable parameters such as molecular weight, branch density, and melting point. Furthermore, catalysts Ni4-Ni6 also possess the ability to catalyze the reaction of ethylene with polar monomers.

[0106] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An α-diimine nickel catalyst with rigid steric hindrance formed by a distal triphenylmethyl group, characterized in that: Its structure is one of Ni4, Ni5, and Ni6, and the specific structural formulas of Ni4, Ni5, and Ni6 are as follows: 、 、 。 2. A method for preparing the α-diimine nickel catalyst of claim 1, characterized by the rigid steric hindrance formed by the distal triphenylmethyl group: The step involves reacting a diimine ligand and an equimolar amount of (DME)NiBr2 in an organic solvent at room temperature, with the reaction carried out under a gas atmosphere; wherein the diimine ligand is one of the following structural formulas: 、 、 。 3. The application of the α-diimine nickel catalyst with rigid steric hindrance formed by the distal triphenylmethyl group as a catalyst for olefin polymerization reaction as described in claim 1, characterized in that: The olefin polymerization reaction is either a homopolymerization of ethylene or a copolymerization of ethylene with a polar monomer, wherein the polar monomer is methyl undecenoate.

4. The application according to claim 3, characterized in that: olefins During the polymerization reaction, a nickel complex based on a diimine ligand is used as a catalyst, and alkyl aluminum chloride is used as a co-catalyst, wherein the alkyl aluminum chloride is diethyl aluminum chloride or ethyl aluminum dichloride.

5. The application according to claim 3, characterized in that: The molar ratio of aluminum in the co-catalyst to nickel in the catalyst is 100-5000:

1.

6. The application according to any one of claims 3-5, characterized in that: The olefin polymerization reaction includes the following steps: adding the polymerization monomer and organic solvent into a reaction vessel, adding a catalyst, a co-catalyst and an activator, controlling the reaction temperature to carry out the reaction, and washing and drying the obtained polymer after the reaction to obtain polyolefin.

7. The application according to claim 6, characterized in that: During the homopolymerization of ethylene, the pressure of ethylene in the reactor is 0-20 atmospheres; during the copolymerization, the pressure of ethylene in the reactor is 0-20 atmospheres, and the concentration of polymerization monomers other than ethylene in the organic solvent is 0.1-5 mol / L.

8. The application according to claim 3, characterized in that: The temperature for olefin polymerization is -20°C to 200°C, and the reaction time is 10 to 60 minutes.

9. The application according to claim 6, characterized in that: The organic solvent is toluene, xylene, or heptane.

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