Preparation method of diimine nickel catalyst containing rigid triphenylmethyl group and application of diimine nickel catalyst in olefin polymerization

Abstract

A series of diimine nickel catalysts provided with far-end rigid triphenylmethyl are provided, and accurate regulation and control of the performance of the catalyst are achieved by introducing functional groups with different electronic effects and steric hindrance. The elaborately designed catalysts not only show excellent activity and excellent thermal stability, but also can efficiently catalyze ethylene polymerization to generate a polyethylene elastomer with adjustable parameters such as molecular weight, branched chain density, melting point and the like. In addition, the copolymer also has the unique capability of catalyzing the copolymerization of ethylene and polar monomers. The introduction of the series of innovative catalysts opens up a brand new path for the development of polyolefin elastomers, and provides a valuable alternative choice.

Description

Technical Field

[0001] The invention belongs to the field of polyolefin metal catalysts, and in particular relates to a method for preparing a nickel catalyst with long-range rigid steric hindrance and an application of the catalyst in preparing an ethylene / polar monomer copolymer. Background Art

[0002] Since Brookhart discovered α-diimine catalysts in the 1990s, this type of catalyst has received sufficient 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 gives polyethylene an adjustable topological structure, melting point and molecular weight. However, the classic α-diimine system also has the problem of low thermal stability and is easily decomposed and deactivated at high temperatures, resulting in a significant reduction in molecular weight. Therefore, a large number of studies have 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 effect of α-diimine ligands are two key factors affecting the performance of catalysts. The presence of a bulky substituent at the ortho position of aniline can effectively block the axial position of the metal center and inhibit chain transfer, thereby improving thermal stability and obtaining a polymer with high molecular weight and low branching density (Turney, KM; Kaewdeewong, P.; Eagan, JM Ethylene Polymerization 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 used in the design of α-diimine catalysts. For example, Brookhart and Daugulis et al. used the bulkier 8-p-methylnaphthalene to replace the α-diimine ligand to synthesize a nickel catalyst, which has a larger axial volume compared to the classic α-diimine nickel catalyst, thereby obtaining a higher polyethylene molecular weight (up to 178.1×10 4 g mol -1 ). Long et al. introduced diisopropylphenyl into the α-diimine ligand, which increased the axial steric hindrance of the nickel catalyst and significantly improved the high thermal stability and polymerization activity of the nickel catalyst. The introduction of the diisopropyl substituent provided an important advance in the development of late transition metal catalysts, and subsequently a series of large steric α-diimine nickel and palladium catalysts were designed and synthesized. Subsequently, Chen reported a series of α-diimine Pd complexes with electron-donating and electron-withdrawing substituents to synthesize 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-p-tert-butylphenyl, which further regulated the topological structure of the polymer through electronic effects, and used these complexes to copolymerize ethylene with polar monomers to prepare thermoplastic elastomers with good performance. In summary, after discovering the significant influence of the diisopropyl substituent, research on further designing transition metal catalyst ligands based on it is still booming (Liu, YS; Harth, E. Distorted Sandwich α-Diimine PdIIC Catalyst: 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 high molecular 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 still expected to improve the performance of nickel-catalyzed ethylene polymerization. In particular, polyethylene elastomers with excellent elastic properties were synthesized using a series of diimine nickel catalysts with ethylene as the only raw material. Further adjustment of the ligand structure of diimine nickel catalysts can make polyolefin elastomers have 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 the present invention, we install triphenylmethyl groups at the para position of α-diimine nickel catalysts to form a remote rigid steric hindrance, and together with the groups near the metal center, form a larger steric hindrance to adjust the polymerization performance of the nickel catalyst. In addition, different diisopropyl substituents are designed to further accurately adjust the polymerization activity of the nickel catalyst, the molecular weight and branch density of polyethylene. Moreover, these nickel catalysts prepare polyolefin elastomers with excellent mechanical and elastic properties, and also realize the copolymerization of ethylene with a series of polar monomers. Summary of the invention

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

[0007] The specific technical solutions of the present invention are as follows:

[0008] An α-diimine nickel catalyst having a remote rigid steric hindrance formed by a triphenylmethyl group, and its structural formula is shown below:

[0009]

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

[0011] The present invention also provides a method for preparing an α-diimine nickel catalyst having a far-end rigid steric hindrance formed by a triphenylmethyl group of the above structural formula. The catalyst is obtained by reacting a diimine ligand and 1.5 times the equivalent 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 the precipitation is complete, the product is filtered, washed, and dried to obtain the α-diimine nickel catalyst having a far-end rigid steric hindrance formed by a triphenylmethyl group.

[0012] Furthermore, the structure of the diimine ligand with a remote rigid steric hindrance formed by a triphenylmethyl group is as follows, R1 is a hydrogen group, a methyl group, an ethyl group, an isopropyl group, a diphenylmethyl group, a phenyl group, a 4,4'-difluorodiphenylmethyl group, or a 4,4'-di-tert-butyldiphenylmethyl group; and R2 is an alkane.

[0013]

[0014] Furthermore, the diimine ligand can be synthesized by a method disclosed in the prior art, and specifically can be synthesized by 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, comprising reacting aniline and trityl chloride in a molar ratio of 10:1 at a temperature of 220°C for 10 minutes, cooling the reactant to room temperature, adding appropriate amounts of methanol and hydrochloric acid solution, and then heating the reactant to reflux for 10 minutes. After cooling, filtering, washing, and drying the precipitate to obtain tetraphenylamine.

[0016] The present invention is based on the fact that the α-diimine nickel catalyst with a remote rigid steric hindrance formed by a triphenylmethyl group exhibits high catalytic performance in olefin polymerization, so its application as an olefin polymerization catalyst is also within the protection scope of the present invention. When it is used as a catalyst, it can catalyze ethylene homopolymerization, and can also catalyze ethylene and polar monomer copolymerization, such as ethylene and methyl undecylenate copolymerization, wherein the polar monomer refers to a monoolefin containing heteroatoms, and the double bond is at the end of the molecular chain.

[0017] Furthermore, in the olefin polymerization reaction, an α-diimine nickel catalyst having a remote rigid steric hindrance formed by a triphenylmethyl group and an alkylaluminum chloride as a co-catalyst are used, and the polymerization monomer undergoes a polymerization reaction under the joint action of these substances.

[0018] Furthermore, the alkylaluminum chloride is diethylaluminum chloride (Et2AlCl) or ethylaluminum dichloride (EtAlCl2), preferably diethylaluminum chloride.

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

[0020] Furthermore, the olefin polymerization reaction can be carried out in any solvent that has no adverse effect on the catalyst system, such as toluene, xylene, alkane solvents, etc. Organic solvents have no significant effect on product performance. During polymerization, the pressure of the polymerization monomer ethylene and the concentration of the polar monomer can be adjusted as needed.

[0021] Furthermore, the olefin polymerization reaction comprises the following steps: adding polymerization reaction monomers and an organic solvent into a reaction kettle, adding a catalyst and a co-catalyst thereto, controlling the reaction temperature to react, and washing and drying the obtained polymer after the reaction to obtain a polyolefin.

[0022] Furthermore, the reaction temperature is 0°C-200°C. The reaction temperature has an effect on the molecular weight and other properties of the product, and is preferably 30°C-120°C. The reaction time is generally 10-60 min depending on the monomer.

[0023] Furthermore, during the homopolymerization of ethylene, the polymerization monomer is ethylene, ethylene is introduced into the reactor, and the pressure of ethylene in the reactor is 0-20 atmospheres, which affects performance indicators such as product molecular weight and degree of branching, and is preferably 8 atmospheres; during the copolymerization, the polymerization monomers are ethylene and polar monomers, the pressure of ethylene in the reactor is 0-20 atmospheres, preferably 8 atmospheres, and the concentration of other polymerization monomers (methyl undecylenate) 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The catalyst single crystal of Example 4;

[0026] Figure 2 The catalyst single crystal of Example 5;

[0027] Figure 3 is the H NMR spectrum of the ligand (L4) of Example 4 of the present invention;

[0028] Figure 4 is the NMR carbon spectrum of the ligand (L4) of Example 4 of the present invention;

[0029] Figure 5 is the H NMR spectrum of the ligand (L5) of Example 5 of the present invention;

[0030] Figure 6 is the NMR fluorine spectrum of the ligand (L5) of Example 5 of the present invention;

[0031] Figure 7 is the NMR carbon spectrum of the ligand (L5) of Example 5 of the present invention; DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0034] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0035] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0036] In the following examples, the ligands used were synthesized according to the method in the reference (Menglong G, Shizhen D, Qing B. Ethylene polymerization by 2,3-diiminobutylnickel bromide pre-catalysts bearing remotebenzhydryl substituents. J. Organomet. Chem. 2015, 798: 401–407), and the steps were as follows: acenaphthenequinone, ZnCl2 and a certain amount of glacial acetic acid solution were added to a round-bottom flask, heated to reflux until the acenaphthenequinone was completely dissolved, and aniline containing different substituents was added to the flask after cooling slightly, and then heated to reflux for several hours. Cool to room temperature, filter with a Buchner funnel, wash the filter cake with ether 2-3 times, dissolve with CH2Cl2, and then add saturated potassium oxalate solution. After the reaction is completed, separate the organic phase, concentrate, and recrystallize to obtain the ligand.

[0037] Example 1

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

[0039]

[0040]

[0041] Step 1: Add 1 eq. of triphenylmethane and 11 eq. of 2,4-dimethylaniline into the same round-bottom flask and reflux at 220°C for 30 min. Then cool the reactant 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 acenaphthenequinone 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 completed, 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 ether. Dissolve the filter cake with dichloromethane, add an excess of saturated potassium oxalate aqueous solution, stir for 3 h, extract the organic phase with water three times, dry the organic phase, evaporate the excess solvent, and recrystallize with 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 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, and finally recrystallize with dry n-hexane, wash the product with ether (4×5 mL), and dry it under vacuum to obtain an orange-red or brown-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-trityl group:

[0048]

[0049] Step 1: The preparation method is the same as Example 1, except that the reactant aniline is replaced by 2,4-diethylaniline, product (65% yield). 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: Preparation method is the same as Example 1, 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 that of Example 1. Finally, an orange-red or brown-red solid is obtained, which is the nickel complex Ni2 (86% yield). 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-trityl group:

[0056]

[0057]

[0058] Step 1: The preparation method is the same as that of Example 1, except that the reactant aniline is replaced by 2,4-diisopropylaniline, product (50% yield). 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: Preparation method is the same as Example 1, 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 that of Example 1. Finally, an orange-red or brown-red solid is obtained, which is the nickel complex Ni3 (86% yield). 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-trityl group:

[0065]

[0066] Step 1: Add 1 eq. of triphenylmethylaniline and 2.1 eq. of benzhydrol into the same pressure bottle, heat to 160°C to melt the reactants, then dissolve 0.5 eq. of zinc chloride in an appropriate amount of hydrochloric acid solution, add it into the pressure bottle, and react for 1 hour. The reactants are cooled to room temperature, extracted three times with dichloromethane and water, the organic phase is collected and dried with anhydrous sodium sulfate, the excess solvent is evaporated, and then recrystallized with 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 that of Example 1, 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 that of Example 1. Finally, the orange-red or brown-red solid obtained is the nickel complex Ni4 (80% yield), and its single crystal structure is shown in Figure 1. 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-trityl group:

[0075]

[0076] Step 1: The preparation method is the same as that of Example 4, except that the reactant aniline is replaced by 4,4'-difluorobenzhydrol, product (54% yield). 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 that of Example 1, 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 that of Example 1. Finally, the orange-red or brown-red solid obtained is the nickel complex Ni5 (84% yield), and its single crystal structure is shown in Figure 2. 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-trityl group:

[0085]

[0086] Step 1: The preparation method is the same as that of Example 4, except that the reactant aniline is replaced by 4,4'-di-tert-butylbenzhydrol, product (30% yield). 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 that of Example 1, 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 that of Example 1. Finally, an orange-red or brown-red solid is obtained, which is the nickel complex Ni5 (86% yield). 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] The catalysts prepared in Examples 4-6 were respectively used to carry out ethylene polymerization, and the specific polymerization method is as follows:

[0093] In a glove box, and under a nitrogen atmosphere, 30 mL of toluene was added to a 300 mL autoclave (with a stirring device, a heating device and a thermometer), and then the container was connected to a high-pressure pipeline and the pipeline was evacuated, and the container temperature was set to the desired temperature and kept warm for 5 minutes; first, 0.5 ml of diethylaluminum chloride (2 mol / L) was injected into the autoclave through a syringe, and then 1.0 umol of the catalyst prepared in Example 4-6 was dissolved in 1.0 mL of dichloromethane and injected into the autoclave through a syringe; then the ethylene valve was opened, ethylene was introduced into the autoclave, and the ethylene pressure was adjusted to 8 atmospheres, and the reaction was carried out for 10 minutes; then the reaction was stopped, the autoclave was opened, ethanol was added to the autoclave to precipitate the solid, the solid was filtered under reduced pressure, and the white solid was dried in a vacuum drying oven.

[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 unit of catalytic activity is kg polyethylene / mol catalyst·h; B is the branching degree of the polymer, the unit is B / 1000C.

[0098] Example 8

[0099] The catalysts prepared in Examples 4-6 were used to copolymerize ethylene and UCOOMe, respectively. The specific polymerization method is as follows:

[0100] In a glove box, and under a nitrogen atmosphere, a polar monomer solution with toluene as a solvent was added to a 300 mL autoclave (with a stirring device, a heating device and a thermometer), and then the container was connected to a high-pressure pipeline and the pipeline was evacuated, and the container temperature was set to the desired temperature and kept warm for 5 minutes; first, 5.0 ml of diethylaluminum chloride (2 mol / L) was injected into the autoclave through a syringe, and then 5.0 umol of the catalyst prepared in Example 4-6 was dissolved in 1.0 mL of dichloromethane and injected into the autoclave through a syringe; then the ethylene valve was opened, ethylene was introduced into the autoclave, and the ethylene pressure was adjusted to 8 atmospheres, and the reaction was carried out for 10 minutes; then the reaction was stopped, the autoclave was opened, ethanol was added to the autoclave to precipitate the solid, the vacuum filter was filtered, and the white solid was dried in a vacuum drying oven.

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

[0102] Table 2 Nickel catalyst catalyzes the copolymerization of ethylene and UCOOMe

[0103]

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

[0105] In summary, the present invention introduces a series of nickel diimide catalysts equipped with remote rigid trityl groups, which achieve precise control of the performance of nickel catalysts by introducing functional groups with different electronic effects and steric hindrance. Under the same polymerization conditions, relative to the catalysts Ni1-Ni3 in Examples 1-3, the catalysts Ni4-Ni6 in Examples 4-6 not only exhibit excellent activity and outstanding thermal stability, but also can efficiently catalyze ethylene polymerization to generate polyethylene elastomers with adjustable parameters such as molecular weight, branch density, and melting point. In addition, catalysts Ni4-Ni6 also have the ability to catalyze ethylene and polar monomers.

[0106] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An α-diimine nickel catalyst having a rigid steric hindrance formed by a remote trityl group, characterized in that: Its structure As shown in Ni below, R is an alkane, and R1 is preferably a hydrogen group, a methyl group, an ethyl group, an isopropyl group, a phenyl group, a diphenylmethyl group, a 4,4'-difluorodiphenylmethyl group, or a 4,4'-di-tert-butyldiphenylmethyl group.

2. The nickel complex based on diimine ligand according to claim 1, characterized in that: It has a rigid steric hindrance formed by a remote trityl group, wherein R is an alkane, and R1 is preferably methyl, ethyl, isopropyl, diphenylmethyl, 4,4'-difluorodiphenylmethyl, 4,4'-di-tert-butyldiphenylmethyl, and most preferably 4,4'-di-tert-butyldiphenylmethyl.

3. A method for preparing a nickel complex based on a diimine ligand according to claim 1, characterized in that : It includes the steps of reacting a diimine ligand and an equimolar amount of (DME)NiBr2 in an organic solvent at room temperature, and the reaction is carried out under gas protection: the diimine ligand has a structural formula as shown in the following formula L, R is an alkane, and R1 is a hydrogen group, a methyl group, an ethyl group, an isopropyl group, a phenyl group, a dibenzhydryl group, a 4,4'-difluorodibenzhydryl group, or a 4,4'-di-tert-butyldibenzhydryl group.

4. The use of the nickel complex based on diimine ligand as claimed in claim 1 as an olefin polymerization catalyst, characterized in that: The olefin polymerization reaction is ethylene homopolymerization, or ethylene and a polar monomer, such as methyl undecylenate.

5. The use according to claim 4, characterized in that: olefin During the polymerization reaction, a nickel complex based on diimine ligand is used as a catalyst, and an alkylaluminum chloride is used as a co-catalyst. The alkylaluminum chloride is diethylaluminum chloride or ethylaluminum dichloride.

6. The use according to claim 4, characterized in that: The molar ratio of aluminum in the co-catalyst to nickel in the catalyst is 100-5000:1, preferably 500-1000:

1.

7. The use according to any one of claims 4 to 6, characterized in that: The olefin polymerization reaction comprises the following steps: adding polymerization reaction monomers and organic solvent into a reaction kettle, adding a catalyst, a co-catalyst and an activator thereto, controlling the reaction temperature to react, and washing and drying the obtained polymer after the reaction to obtain polyolefin.

8. The use according to claim 7, characterized in that: During the homopolymerization of ethylene, the pressure of ethylene in the reactor is 0-20 atmospheres, preferably 8 atmospheres; during the copolymerization, the pressure of ethylene in the reactor is 0-20 atmospheres, preferably 8 atmospheres, and the concentration of polymerization monomers other than ethylene in the organic solvent is 0.1-5 mol / L, preferably 0.1-2 mol / L.

9. The use according to claim 4 or 7, characterized in that: olefin The polymerization reaction temperature is -20°C to 200°C, preferably 30°C to 120°C, and the reaction time is 10 to 60 minutes.

10. The use according to claim 7, characterized in that: The organic solvent is toluene, xylene or heptane.

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