Cyclic dinuclear bulky diimine nickel catalysts and ligands, methods of making and use thereof

Abstract

The application discloses a novel cyclic binuclear large steric hindrance diimine nickel catalyst and a ligand, a preparation method and an application thereof. The novel cyclic binuclear large steric hindrance diimine nickel catalyst successfully integrates a macrocycle, a bimetal center and a large steric hindrance substituent structure, the ligand can realize synthesis on a kilogram scale, and good solubility is shown. The obtained catalyst catalyzes ethylene polymerization and copolymerization with a polar monomer, not only the activity and thermal stability are significantly improved, but also the chain walking process can be precisely controlled, and low-branched, high-melting-point and only-methyl-branched semi-crystalline polyethylene and high-insertion-rate polar functionalized polyethylene materials are generated.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and catalysts, specifically to a cyclic, sterically hindered nickel diimine catalyst, its ligands, preparation method, and applications. Background Technology

[0002] Polyethylene and its copolymers are among the most widely used polymer materials. Their mechanical and thermal properties largely depend on the degree of branching and the distribution of the molecular chains. Generally, linear or low-branched polyethylene has higher crystallinity and melting point, making it suitable as a semi-crystalline thermoplastic material, while high-branched polyethylene has lower crystallinity and a lower melting point, limiting its application range.

[0003] Post-transition metal catalysts such as α-diimine nickel and palladium provide an important technical route for olefin polymerization. These catalysts offer advantages such as good tolerance to polar functional groups, mild reaction conditions, and the ability to obtain high molecular weight polymers. However, these catalysts generally undergo isomerization chain walk processes initiated by β-hydrogen elimination and re-insertion during polymerization. For example, one chain walk produces methyl branches, two consecutive chain walks produce ethyl branches, and so on. This easily leads to high branching under ethylene homopolymerization conditions, resulting in lower crystallinity and melting point of the obtained polyethylene. Furthermore, polyethylene obtained using traditional α-diimine nickel catalysts typically contains multiple types of branches with complex branch distributions, making it difficult to precisely control material properties. Existing research has shown that the relationship between chain walk rate and chain growth rate can be influenced by catalyst structure design and reaction condition adjustment, thereby controlling the branching degree and branch distribution of polyethylene within a certain range. For example, introducing sterically hindered ligands, changing polymerization temperature and pressure, or adding polar additives can achieve the synthesis of polyethylene ranging from low-branched to high-branched and even ultra-high-branched. However, in most cases, it is difficult to achieve a combination of properties such as low branching, single branch type, and high melting point at the same time.

[0004] Bimetallic catalytic systems are considered an effective strategy for improving catalytic performance and regulating polymer microstructure due to the potential synergistic effect between the two metal centers. In existing technologies, binuclear α-diimine nickel or palladium catalysts often connect the two metal centers through bridging units, which improves catalytic activity and polymer molecular weight to some extent. However, the bridging units typically only serve a structural connection function, contributing little to the axial steric hindrance of the active center. Furthermore, macrocyclic ligands, due to their rigidity and confined structure, have advantages in improving catalyst stability and influencing monomer insertion behavior. However, there are few reports on α-diimine catalysts combining macrocyclic structures with bimetallic systems, and existing macrocyclic systems generally suffer from complex ligand synthesis, poor solubility, and insufficient steric hindrance at the active center.

[0005] Therefore, there is an urgent need to develop a new α-diimine catalyst design strategy that can effectively integrate macrocyclic structures, bimetallic centers, and large axial steric hindrance features while ensuring synthetic feasibility, so as to achieve precise control of the chain walking process and obtain polyethylene and its polar functionalized polyethylene materials with high molecular weight, low branching degree, high melting point and controllable branching type. Summary of the Invention

[0006] In view of the above, the purpose of this invention is to provide a novel cyclic binuclear sterically hindered diimine ligand and a corresponding nickel catalyst, as well as its preparation method and uses. This catalyst has high thermal stability and high activity in olefin polymerization and can prepare high molecular weight and low branching polyolefins.

[0007] The first objective of this invention is to provide a method for synthesizing cyclic binuclear diimine nickel catalysts and their ligands.

[0008] The second objective of this invention is to provide a method for preparing polyolefin materials by polymerization using a cyclic binuclear diimine nickel catalyst.

[0009] A third object of the present invention is to provide a polyolefin material prepared according to the method.

[0010] This invention provides a cyclic binuclear sterically hindered nickel diimine complex of formula (Ni), with the following structure: ; Where R is H or CHAr2; when R is CHAr2, Ar is 4-tert-butylphenyl ( ) or other 4-alkylphenyl ( ), 4-methoxyphenyl ( )wait.

[0011] The synthesis reaction formulas for the cyclic binuclear sterically hindered nickel diimine catalysts Ni1 and Ni2 are as follows (where Ni3 and Ni4 are comparative examples): .

[0012] The specific preparation method includes the following process steps: (1) Preparation of hydrogen-substituted (R=H) dinuclear amines: 1,4-phenylenediboric acid and 2-bromo-4-(tert-butyl)aniline were mixed with sodium carbonate and tetra(triphenylphosphine)palladium in a molar ratio of 1:2. A mixed solvent of toluene, ethanol and water was added, and the mixture was heated to 80°C and refluxed for 24 hours. After the reaction was completed, the reaction solution was filtered with diatomaceous earth, the filtrate was extracted with water, and dried over anhydrous magnesium sulfate. The solution was concentrated, recrystallized with methanol and washed, and filtered to obtain hydrogen-substituted dinuclear amine powder.

[0013] (2) CHAr2 substitution (R = Preparation of sterically hindered diarylamine intermediates: Hydrogen-substituted dinuclear amines and 4,4'-di-tert-butyldiphenylmethanol ( Rhenium heptaoxide and hexafluoroisopropanol were heated and stirred at 80°C for 12 hours, and then directly filtered to obtain a sterically hindered bis(aryl) amine intermediate powder substituted with tert-butylphenyl.

[0014] (3) Preparation of hydrogen-substituted (R = H) cyclic binuclear sterically hindered diimine ligands: A substituent-containing binuclear amine and 2,3-butanedione were mixed in a 1:1 molar ratio, and 0.02 equivalents of p-toluenesulfonic acid were added. The mixture was refluxed at 120°C for 72 hours using toluene as the solvent. After the reaction was completed, the reaction solution was directly filtered to obtain a yellow powder.

[0015] (4) CHAr2 substitution (R = Preparation of a cyclic binuclear sterically hindered diimine ligand: A sterically hindered diarylamine intermediate containing substituents was mixed with 2,3-butanedione in a 1:1 molar ratio, and 0.02 equivalents of p-toluenesulfonic acid were added. The mixture was refluxed at 80 °C for 48 hours using toluene as the solvent. Subsequently, a water separator was added to the apparatus, and the mixture was refluxed at 120 °C for 72 hours. After the reaction was completed, the reaction solution was separated by column chromatography. The pure product was obtained as a yellow powder. This ligand has good solubility in n-hexane (0.1 g / mL).

[0016] (5) Preparation of cyclic binuclear sterically hindered diimine nickel complex: Under nitrogen protection, dichloromethane was used as solvent to mix the cyclic binuclear diimine ligands obtained in (3) and (4) above with (DME)NiBr2 at a molar ratio of 1:2. The mixture was stirred at room temperature for 12 hours, then hexane was added and recrystallized to obtain a red solid complex.

[0017] Beneficial effects (1) This invention provides a novel binuclear sterically hindered diimine nickel catalyst with binuclear / cyclic structure / sterically hindered substituent function by introducing a sterically hindered substituent at the ortho position of the aniline structure to form a cyclic binuclear diimine ligand and a corresponding nickel metal complex. The ligand has a simple synthetic route, good solubility, and can be synthesized at the gram scale.

[0018] (2) The cyclic binuclear sterically hindered nickel diimine catalyst of the present invention exhibits higher catalytic activity and thermal stability compared to the mononuclear catalyst in the catalytic polymerization reaction of ethylene, and can obtain ultra-high molecular weight polyethylene (molecular weight of 1.59 × 10⁻⁶). 6The branching degree of the resulting polyethylene was significantly reduced and the melting point was increased (g / mol). In particular, compared with mononuclear catalysts, the cyclic binuclear sterically hindered catalyst of the present invention significantly improved the catalytic activity and molecular weight of the resulting copolymer in the copolymerization of ethylene and polar monomers, and the polar monomer insertion rate could reach as high as 8.9%.

[0019] (3) The cyclic binuclear sterically hindered diimine nickel catalyst of the present invention produces a polymer containing only methyl branches in the catalytic polymerization reaction of ethylene. Even under high temperature polymerization conditions of 80°C, only methyl branches are present, which can precisely control the chain walking process. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the single crystal structure of the 4-tert-butylphenyl-substituted cyclic binuclear sterically hindered diimine nickel catalyst synthesized according to Example 2 of the present invention. Figure 2 This is the 1H NMR spectrum of the hydrogen-substituted dinuclear amine synthesized according to Example 1 of the present invention; Figure 3 This is the carbon NMR spectrum of the hydrogen-substituted dinuclear amine synthesized according to Example 1 of the present invention; Figure 4 This is the 1H NMR spectrum of the hydrogen-substituted cyclic dinuclear diimine ligand synthesized according to Example 1 of the present invention; Figure 5 This is the 1H NMR spectrum of the hydrogen-substituted cyclic dinuclear diimine nickel catalyst synthesized according to Example 1 of the present invention; Figure 6 This is the 1H NMR spectrum of the 4-tert-butylphenyl-substituted sterically hindered diarylamine intermediate synthesized according to Example 2 of the present invention; Figure 7 This is the carbon NMR spectrum of the 4-tert-butylphenyl-substituted sterically hindered diarylamine intermediate synthesized according to Example 2 of the present invention; Figure 8 This is the 1H NMR spectrum of the 4-tert-butylphenyl substituted cyclic binuclear sterically hindered diimine ligand synthesized according to Example 2 of the present invention; Figure 9 This is the carbon NMR spectrum of the 4-tert-butylphenyl substituted cyclic binuclear sterically hindered diimine ligand synthesized according to Example 2 of the present invention; Figure 10 This is the 1H NMR spectrum of the 4-tert-butylphenyl substituted cyclic binuclear sterically hindered diimine nickel catalyst synthesized according to Example 2 of the present invention; Figure 11 This is the carbon NMR spectrum of the 4-tert-butylphenyl substituted cyclic binuclear sterically hindered diimine nickel catalyst synthesized according to Example 2 of the present invention; Figure 12 This is the mass spectrum of the hydrogen-substituted cyclic binuclear sterically hindered diimine ligand synthesized according to Example 1 of the present invention; Figure 13 This is the mass spectrum of the hydrogen-substituted cyclic binuclear sterically hindered diimine nickel catalyst synthesized according to Example 1 of the present invention; Figure 14 This is the mass spectrum of the 4-tert-butylphenyl substituted cyclic binuclear sterically hindered diimine ligand synthesized according to Example 2 of the present invention; Figure 15 This is the mass spectrum of the 4-tert-butylphenyl substituted cyclic binuclear sterically hindered diimine nickel catalyst synthesized according to Example 2 of the present invention; Figure 16 The carbon NMR spectrum of the polymer obtained by homopolymerization of ethylene at 30°C using the nickel complex obtained in Example 1 of this invention as a catalyst; Figure 17 The carbon NMR spectrum of the polymer obtained by homopolymerization of ethylene at 30°C using the nickel complex obtained in Example 2 of this invention as a catalyst; Figure 18 The carbon NMR spectrum of the polymer obtained by homopolymerization of ethylene at 55°C using the nickel complex obtained in Example 2 of this invention as a catalyst; Figure 19 The carbon NMR spectrum of the polymer obtained by homopolymerization of ethylene at 80°C using the nickel complex obtained in Example 2 of this invention as a catalyst; Figure 20 The NMR chromatogram of the polymer obtained by homopolymerization of ethylene at 30°C using the nickel complex obtained in Comparative Example 2 of this invention as a catalyst. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Through systematic experiments and in-depth research, the inventors of this invention discovered that when a sterically hindered substituent is introduced into the aniline structure of a binuclear diimine ligand to form a cyclic structure, the resulting cyclic binuclear sterically hindered diimine nickel catalyst not only exhibits high catalytic activity and high thermal stability in the catalytic polymerization of low-carbon olefins, but also significantly increases the molecular weight of the resulting polyolefin product.

[0023] The cyclic binuclear sterically hindered nickel diimine catalyst has the following structural formula (Ni): .

[0024] In some embodiments, the substituent R is H or CHAr2; when R is CHAr2, Ar is 4-tert-butylphenyl (HH). ) or other 4-alkylphenyl ( ), 4-methoxyphenyl ( )wait.

[0025] More preferably, in some embodiments, R is H or CHAr2; when R is CHAr2, Ar is 4-tert-butylphenyl ( ).

[0026] For example: In some embodiments, preferably, the co-catalyst is diethylaluminum chloride, methylaluminoxane, or modified methylaluminoxane.

[0027] More preferably, the co-catalyst is diethylaluminum chloride.

[0028] In some embodiments, preferably, the polar monomer is methyl 10-undecenoate, methyl 10-undecenoic acid, methyl 9-decaenoate, acrylic acid, methyl acrylate, or 10-undecenool.

[0029] More preferably, the polar monomer is methyl 10-undecenoate.

[0030] In some embodiments, preferably, the molar ratio of the main catalyst to the co-catalyst is 1:50 to 1000.

[0031] More preferably, the molar ratio of the main catalyst to the co-catalyst is 1:600.

[0032] In some embodiments, preferably, the molar ratio of the olefin to the polar monomer is 100:0.1 to 20.

[0033] More preferably, the molar ratio of the olefin to the polar monomer is 100:2.

[0034] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0035] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0036] In the following examples, the number-average molecular weight of the prepared polymers was determined by gel permeation chromatography (GPC). M n Unit g·mol -1 The molecular weight distribution index (PDI) was also measured. Melting point and crystallinity were determined by differential scanning calorimetry (DSC). The sample was rapidly heated to 150 °C, held for 5 minutes to remove thermal history, then cooled to -70 °C at a rate of 10 °C / min, and finally reheated to 150 °C at the same rate under a nitrogen flow (50 mL / min). The maximum absorbance point (heating scan) was taken as the melting point (T). mBranching degree, measured as the number of branches per 1000 carbon atoms, is determined by proton nuclear magnetic resonance (NMR) spectroscopy. 1 The polar monomer insertion rate was obtained by H NMR (hydrogen permeation) testing. 1 The measurements were performed using 1H NMR.

[0037] Example 1: Synthesis of hydrogen-substituted cyclic dinuclear diimine nickel complex (Ni1, R=H) 1. Synthesis of hydrogen-substituted dinuclear amines (A1, R=H) The preparation reaction formula is as follows: In a 500 mL Schlenk flask, 2-bromo-4-(tert-butyl)aniline (16.43 g, 72 mmol, 2 equivalents), 1,4-phenylenediboronic acid (5.97 g, 36 mmol, 1 equivalent), sodium carbonate (15.82 g, 149.3 mmol, 4.1 equivalents), and tetrakis(triphenylphosphine)palladium (0.998 g, 0.86 mmol, 0.023 equivalents) were added. A mixed solvent of toluene / ethanol / water (180 mL, 60 mL, 60 mL, v / v) was added to the reaction flask. The Schlenk flask was sealed, and the reaction mixture was stirred and refluxed at 80 °C for 24 hours under nitrogen. The reaction was accompanied by a color change from pale yellow to reddish-brown. The mixture was cooled to room temperature, and the crude product was extracted with dichloromethane. The organic phase was washed three times with water, dried over anhydrous MgSO4, distilled under reduced pressure to a minimum, recrystallized from n-hexane, and filtered to give a deep purple solid crude product. The crude product was washed with methanol to obtain the target product as a white solid, with a yield of 37%.

[0038] NMR analysis: 1 ¹H NMR (500 MHz, chloroform-d) δ 7.56 (s, 4H, Ar- H ), 7.23-7.20(m, 4H, Ar- H ), 6.76 (d, J = 8.1 Hz, 2H, Ar- H ), 3.73 (s 4H, N H 2), 1.32 (s, 18H,tBu). 13 CNMR (126 MHz, chloroform-d) δ 141.80 ( C -N), 140.92 (Ar- C ), 138.82 (Ar- C ),129.60 (Ar- C), 127.34 (Ar- C ), 127.05 (Ar- C ), 125.58 (Ar- C ), 115.76 (Ar- C ),34.28 ( C (CH3)3), 31.68 (C- C H3). 2. Synthesis of hydrogen-substituted cyclic dinuclear diimine ligands (L1, R=H) The preparation reaction formula is as follows: In a 200 mL Schlenk flask, A2 (1.86 g, 5 mmol, 1 equivalent), 2,3-butanedione (0.43 g, 5 mmol, 1 equivalent), and p-toluenesulfonic acid (20 mg, 0.12 mmol, 0.02 equivalent) were added. Anhydrous toluene (40 mL) was then added to the reaction flask. The Schlenk flask was sealed, and the reaction mixture was stirred and refluxed at 120 °C for 24 hours. The reaction solution was directly filtered and washed with methanol to obtain the target product as a pale yellow solid, in 24% yield.

[0039] NMR analysis: 1 ¹H NMR (500 MHz, chloroform-d) δ 7.44 (d, J = 2.1 Hz, 4H, Ar-H), 7.37 (s, 8H, Ar-H), 7.34 (d, J = 2.2 Hz, 2H, Ar-H), 7.32 (d, J = 2.2 Hz, 2H, Ar-H), 6.67 (d, J = 8.3 Hz, 4H, Ar-H), 1.96 (s, 12H, N=C-CH₃), 1.35 (s, 36H, tBu). Due to the low solubility of this ligand in deuterated chloroform, ¹³C NMR was not performed.

[0040] Mass spectrometry analysis: ESI-MS (m / z): calcd for C 60 H 69 N4, 845.5522; found, 845.5526 [M+H] + . 3. Synthesis of hydrogen-substituted cyclic dinuclear diimine nickel complexes (Ni1, R=H) The preparation reaction formula is as follows: Compound L1 (0.15 g, 0.178 mmol, 1 equivalent), nickel acetylacetonate (0.091 g, 0.355 mmol, 2 equivalents), triphenylmethylammonium tetrafluorophenylborate (0.327 g, 0.355 mmol, 2 equivalents), and 10 mL of dichloromethane were added to a 20 mL sample vial. The system was placed in a vacuum glove box and stirred at room temperature for 12 hours, during which the color gradually turned reddish-brown. Volatile substances were removed under vacuum, and the mixture was washed with n-hexane to obtain a reddish-brown solid in 47% yield.

[0041] NMR analysis: 1 H NMR (500 MHz, chloroform-d) δ 8.22 (s, 4H, Ar-H), 7.60(s, 4H, Ar-H), 7.49 (s, 4H Ar-H), 7.16-6.79 (m, J = 2.0 Hz, 8H, Ar-H), 5.08(s, 2H, acac-CH), 1.89 (s, 12H, acac-CH3), 1.35 (s, 36H, tBu), 0.89 (s, 12H, N=C-CH3). Mass spectrometry analysis: MALDI-TOF-MS (m / z): calcd for C 60 H 68 N4Ni, 902.47; found,902.24 [M-2B(C6F5)4-Ni(acac)2] + . Example 2 4-tert-butylphenyl substituted cyclic binuclear sterically hindered diimine nickel complex (Ni2, R= Synthesis of ) 1,4-tert-butylphenyl substituted sterically hindered diarylamine intermediate (A2, R= Synthesis of ) Compound A1 (1.88 g, 5 mmol, 1 equivalent), 4,4'-di-tert-butyldiphenylmethanol (2.98 g, 10 mmol, 2 equivalents), rhenium heptaoxide (25 mg, 0.05 mmol, 0.01 equivalents), and 65 mL of hexafluoroisopropanol were added to a thick-walled, pressure-resistant flask. The mixture was heated and stirred at 80 °C for 12 hours. Direct filtration yielded a white solid in 73% yield.

[0042] NMR analysis: 1 ¹H NMR (500 MHz, chloroform-d) δ 7.55-7.48 (m, 4H, Ar- H), 7.31(d, J = 8.3 Hz, 8H, Ar- H ), 7.11-7.05 (m, 10H, Ar- H ), 7.06 (d, J = 2.1 Hz, 2H, Ar- H ), 6.68 (d, J = 2.1 Hz, 2H, Ar- H ), 5.49 (s, 2H, C H Ar2), 3.57 (s, 4H, N H 2), 1.30(s, 36H, tBu), 1.14 (s, 18H, tBu). 13 CNMR (126 MHz, chloroform-d) δ 148.26 ( C -N), 139.59 (Ar- C ), 138.61 (Ar- C ), 138.02 (Ar- C ), 137.76 (Ar- C ), 128.83 (Ar- C ),128.81 (Ar- C ), 128.72 (Ar- C ), 128.10 (Ar- C ), 126.65 (Ar- C ), 125.77 (Ar- C ),124.23 (Ar- C ), 50.85 ( C HAr2), 33.39 ( C (CH3)3), 32.94 ( C (CH3)3), 30.36 (C- C H3). Mass spectrometry analysis: ESI-MS (m / z): calcd for C 68 H 85 N2, 929.6713; found, 929.4397 [M+H] + . 2,4-tert-butylphenyl substituted cyclic binuclear sterically hindered ligands (L2, R= Synthesis of ) The preparation reaction formula is as follows: In a 200 mL Schlenk flask, A2 (5.0 g, 5.36 mmol, 1 equivalent), 2,3-butanedione (0.46 g, 5.36 mmol, 1 equivalent), and p-toluenesulfonic acid (20 mg, 0.12 mmol, 0.02 equivalent) were added, followed by 200 mL of anhydrous toluene. The Schlenk flask was sealed and refluxed at 80 °C for 24 hours with stirring. Subsequently, a water separator was added to the apparatus, and reflux was carried out at 120 °C for 72 hours. Further purification by silica gel column chromatography yielded the target product as a pale yellow solid in 34% yield.

[0043] NMR analysis: 1 H NMR (500 MHz, chloroform-d) δ 7.13-7.10 (m, 16H, Ar-H), 7.04-7.00 (m, 16H, Ar-H), 6.98 (d, J = 1.9 Hz, 4H, Ar-H), 6.94 (d, J = 1.8Hz, 4H, Ar-H), 6.85 (d, J = 8.2 Hz, 8H, Ar-H), 5.41 (s, 4H, CHAr2), 1.22 (s,36H, tBu), 1.13 (s, 72H, tBu), 0.55 (s, 12H, N=C-CH3). 13 C NMR (126 MHz,chloroform-d) δ 169.71 (C=N), 148.60 (Ar-C), 145.74 (Ar-C), 143.94 (Ar-C), 140.98 (Ar-C), 139.94 (Ar-C), 138.89 (Ar-C), 132.98 (Ar-C), 129.93 (Ar-C), 129.09 (Ar-C), 128.26 (Ar-C), 126.63 (Ar-C), 124.91 (Ar-C), 50.82 (CHAr2), 34.36 (C(CH3)3), 34.31 (C(CH3)3), 34.28 (C(CH3)3), 31.47 (C-CH3), 31.41 (C-CH3), 31.36(C-CH3), 18.08 (N=C-CH3).

[0044] Mass spectrometry analysis: ESI-MS (m / z): calcd for C 144 H 173N4, 1959.3694; found,1959.3710 [M+H] + 3,4-tert-butylphenyl substituted cyclic binuclear sterically hindered nickel diimine complexes (Ni2, R= Synthesis of ) The preparation reaction formula is as follows: Compound L2 (0.2 g, 0.102 mmol, 1 equivalent), nickel acetylacetonate (0.053 g, 0.204 mmol, 2 equivalents), triphenylmethylammonium tetrafluorophenylborate (0.188 g, 0.204 mmol, 2 equivalents), and 10 mL of dichloromethane were added to a 20 mL flask. The system was placed in a vacuum glove box and stirred at room temperature for 12 hours, during which the color gradually turned reddish-brown. Volatile substances were removed under vacuum, and the mixture was washed with n-hexane to obtain a reddish-brown solid in 80% yield.

[0045] NMR analysis: 1 H NMR (500 MHz, chloroform-d) δ 7.65 (s, 8H, Ar-H), 7.36 (d, J = 8.3 Hz, 8H, Ar-H), 7.29 (d, J = 8.7 Hz, 12H, Ar-H), 7.17 (d, J = 8.5Hz, 12H, Ar-H), 6.69 (d, J = 8.3 Hz, 8H, Ar-H), 6.77 (s, 4H, CHAr2), 5.36 (s,2H, acac-CH), 1.36 (s, 12H, acac-CH3), 1.33 (s, 36H, tBu), 1.17 (d, J = 2.6Hz, 72H, tBu), 0.79 (s, 12H, N=C-CH3). 13C NMR (126 MHz, chloroform-d) δ 187.97(C=O), 177.84 (C=N), 152.94 (Ar-C), 150.76 (Ar-C), 150.46 (Ar-C), 149.06 (Ar-C), 147.15 (Ar-C), 139.53 (Ar-C), 138.69 (Ar-C), 137.56 (Ar-C), 134.96 (Ar-C), 133.34 (Ar-C), 130.04 (Ar-C), 128.88 (Ar-C), 128.75 (Ar-C), 127.91 (Ar-C), 126.00 (Ar-C), 125.58 (Ar-C), 53.23 (CHAr2, acac-CH), 34.94 (C(CH3)3),34.53 (C(CH3)3), 34.41 (C(CH3)3) 31.26 (C-CH3), 31.14 (C-CH3), 30.65 (C-CH3),24.13 (acac-CH3), 22.67 (acac-CH3), 18.98 (N=C-CH3), 14.12 (N=C-CH3).

[0046] Mass spectrometry analysis: MALDI-TOF-MS (m / z): calcd for C 149 H 179 N4NiO2, 2115.34; found,2115.29 [M-2B(C6F5)4-Ni(acac)] + . Comparative Example 1: Synthesis of a hydrogen-substituted mononuclear diimine nickel complex (Ni3, R=H) 1. Synthesis of hydrogen-substituted mononuclear diimine ligands (L3, R=H) The preparation reaction formula is as follows: In a 200 mL Schlenk flask, 5-(tert-butyl)-[1,1'-biphenyl]-2-amine (1.0 g, 4.44 mmol, 2 equivalents), 2,3-butanedione (0.19 g, 2.22 mmol, 1 equivalent), and formic acid were added. 40 mL of anhydrous methanol was then added to the reaction flask. The Schlenk flask was sealed, and the reaction mixture was stirred at room temperature for 24 hours. After the reaction was complete, the mixture was filtered to obtain the target product as a pale yellow solid, with a yield of 92%.

[0047] 2. Synthesis of hydrogen-substituted mononuclear diimine nickel complex (Ni3, R=H) Compound L3 (0.2 g, 0.399 mmol, 1 equivalent), nickel acetylacetonate (0.102 g, 0.399 mmol, 1 equivalent), triphenylmethylammonium tetrafluorophenylborate (0.368 g, 0.399 mmol, 1 equivalent), and 10 mL of dichloromethane were added to a 20 mL sample vial. The system was placed in a vacuum glove box and stirred at room temperature for 12 hours, during which the color gradually turned reddish-brown. Volatile substances were removed under vacuum, and the mixture was washed with n-hexane to obtain a reddish-brown solid in 89% yield.

[0048] Comparative Example: 2,4-tert-butylphenyl substituted mononuclear diimine nickel complex (Ni4, R= Synthesis of ) 1,4-tert-butylphenyl substituted mononuclear sterically hindered amine (A3, R= Synthesis of ) The preparation reaction formula is as follows: In a thick-walled, pressure-resistant flask, 1.13 g (5 mmol, 1 equivalent) of 5-(tert-butyl)-[1,1'-biphenyl]-2-amine, 1.5 g (5 mmol, 1 equivalent) of alcohol, 25 mg (0.05 mmol, 0.01 equivalent) of rhenium heptaoxide, and 65 mL of hexafluoroisopropanol were added. The mixture was heated and stirred at 80 °C for 12 hours. After reaction, the mixture was filtered to give a white solid in 87% yield.

[0049] 2,4-tert-butylphenyl substituted mononuclear sterically hindered diimine ligands (L3, R= Synthesis of ) The preparation reaction formula is as follows: In a 200 mL Schlenk flask, A3 (1.5 g, 2.9 mmol, 2 equivalents), 2,3-butanedione (0.13 g, 1.48 mmol, 1 equivalent), and p-toluenesulfonic acid (20 mg, 0.12 mmol, 0.08 equivalents) were added, followed by 40 mL of anhydrous toluene. The Schlenk flask was sealed, and the reaction mixture was refluxed at 120°C for 24 hours with stirring. Further purification by column chromatography yielded the target product as a pale yellow solid, in 20% yield.

[0050] 3,4-tert-butylphenyl substituted mononuclear sterically hindered nickel diimine complex (Ni4, R= Synthesis of ) The preparation reaction formula is as follows: Compound L3 (0.2 g, 0.205 mmol, 1 equivalent), nickel acetylacetonate (0.053 g, 0.205 mmol, 1 equivalent), triphenylmethylammonium tetrafluorophenylborate (0.189 g, 0.205 mmol, 1 equivalent), and 10 mL of dichloromethane were added to a 20 mL sample vial. The reaction system was placed in a vacuum glove box and stirred at room temperature for 12 hours, during which the color gradually turned reddish-brown. Volatile substances were removed under vacuum, and the mixture was washed with n-hexane to obtain a reddish-brown solid in 78% yield.

[0051] Example 3 The autoclave was first dried for at least half an hour. After assembly, the reactor was evacuated to a vacuum and then filled with nitrogen. This process was repeated three times. Ethylene was pressurized to 1.1 atm, and then 48 mL of toluene and 0.6 mL of Et₂AlCl in toluene (1M) were added at the desired temperature. The system was maintained by continuous stirring for 5 minutes. Subsequently, 2 mL of a nickel catalyst solution in dichloromethane was injected, and the ethylene pressure was increased to 8 atm to initiate polymerization. The mixture was continuously stirred at the appropriate temperature for the desired time. The polymerization reaction was quenched by adding acidified methanol (a methanol solution of 5% HCl). The product was precipitated in methanol, filtered, and vacuum dried at 45 °C to constant weight.

[0052] Example 4 First, the autoclave was dried for at least half an hour. After assembly, it was evacuated to a vacuum, then filled with nitrogen. This process was repeated three times. Ethylene was pressurized to 1.1 atm, and then 33 mL of toluene and 0.6 mL of Et₂AlCl in toluene (1 M) were added at the desired temperature. The system was maintained by continuous stirring for 5 minutes. Then, a solution of the polar monomer methyl 10-undecenoate and 2 mL of nickel catalyst in dichloromethane was injected, and the ethylene pressure was increased to 4 atm to initiate polymerization. The mixture was continuously stirred at the appropriate temperature for the required time. The polymerization reaction was quenched by adding acidified methanol (a methanol solution of 5% HCl). The product was precipitated in methanol, filtered, and vacuum dried at 45 °C to constant weight. The table below shows the experimental conditions for ethylene polymerization provided by this invention: catalyst (Cat.), temperature (T), yield (Yield), catalytic activity (Act.), and polymer molecular weight (%). M n Polymer molecular weight distribution (PDI), degree of branching (B), melting point ( T m Aggregated results data such as )

[0053] Table 1. Catalysis of ethylene homopolymerization by different nickel complexes under different polymerization conditions. a Polymerization conditions: 1 μmol nickel, 600 equivalents of diethylaluminum chloride, 2 mL dichloromethane, 48 mL toluene, 8 atm ethylene, reaction time 15 min; b Active Act. b The unit is 10 6 g / (mol h); c polymer molecular weight M n The molecular weight distribution (PDI) was determined by gel permeation chromatography (GPC), with units of 10-1. 4 gmol -1 ; d Branching degree refers to the number of branches per 1000 carbon atoms, determined by... 1 Measured by H NMR nuclear magnetic resonance method; e Melting point T m Measured by differential scanning calorimetry (DSC).

[0054] Table 2 Branching distribution of polymers catalyzed by different nickel complexes a a Branching distribution through 13 The determination was performed using CNMR in C2D2Cl4 at a temperature of 120℃.

[0055] Table 3. Catalysis of ethylene-polar monomer copolymerization by different nickel complexes under different polymerization conditions. a a Polymerization conditions: 20 μmol nickel, 600 equivalents of diethylaluminum chloride, methyl 10-undecenoate (0.3-3.0 mol / L), 2 mL dichloromethane, 33 mL toluene, 4 atm ethylene, reaction time 3 hours; b Active Act. b The unit is 10 4 g / (mol h); c polymer molecular weight M n The molecular weight distribution (PDI) was determined by gel permeation chromatography (GPC), with units of 10-1. 4 gmol -1 ; d Branching degree refers to the number of branches per 1000 carbon atoms, determined by...1 Measured by H NMR nuclear magnetic resonance method; e Melting point T m Measured by differential scanning calorimetry (DSC).

[0056] As shown in Table 1, Example 1 of this invention did not show a significant improvement compared to Comparative Example 1, indicating that the sterically hindered (R=H) cyclic binuclear structure did not enhance catalyst performance. However, Example 2 introduced a bulky substituent CHAr2 at the aryl positions 2 and 6, resulting in a significantly increased molecular weight of polyethylene compared to the less sterically hindered Example 1, exceeding 5.7 × 10⁻⁶. 5 g / mol, and even ultra-high molecular weight polyethylene (1.59 × 10 g / mol) can be obtained. 6 (g / mol), while the molecular weight distribution was significantly narrowed. Compared with Comparative Example 2, Example 2 exhibited higher activity at the same polymerization temperature, and the enhancement effect was more significant at high temperatures. At 105°C, the activity of Example 2 was approximately 3.5 times that of Comparative Example 2. These results clearly demonstrate that, compared with mononuclear catalysts without cyclic structures, macrocyclic binuclear structures greatly improve the thermal stability of catalysts and effectively suppress chain transfer processes.

[0057] As shown in Table 2, compared to Example 1 with its small sterically hindered binuclear catalyst and Comparative Example 2 with its acyclic mononuclear catalyst, the polymers produced contained methyl branches and long branches. In stark contrast, the polymer produced in Example 2 with its cyclic, heavily sterically hindered binuclear catalyst contained only methyl branches. Even when the polymerization temperatures were increased to 55°C and 80°C, only methyl branches remained. This significant difference indicates that the cyclic, heavily sterically hindered binuclear catalyst has a strong inhibitory effect on chain walking and can precisely control the chain walking process.

[0058] Table 3 shows that at low polar monomer concentrations (0.3 M), the polar monomer insertion rates of Example 2 and Comparative Example 2 are comparable, but the activity of Example 2 is nearly 50 times higher than that of Comparative Example 2, and the molecular weight of the copolymer is approximately four times that of Comparative Example 2. At high polar monomer concentrations (2 M and 3 M), the mononuclear catalyst of Comparative Example 2 is completely inactive, but the cyclic binuclear catalyst of Example 2 remains active with polar monomer insertion rates as high as 4.2% and 8.9%, and even with extremely high insertion rates, the molecular weight remains as high as 16.3 × 10⁻⁶. 4 g / mol and 6.8×10 4 g / mol. Clearly, the superior copolymerization ability of Example 2 mainly stems from its cyclic confinement and binuclear structure, which inhibits chain transfer and prevents the poisoning of ligands by polar monomers, thereby increasing the polar monomer insertion rate and the molecular weight of the resulting polymer.

[0059] The present invention has been described in detail above, but it is not limited to the specific embodiments described herein. Those skilled in the art will understand that other modifications and variations can be made without departing from the scope of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A sterically hindered diarylamine intermediate, as shown in formula (A2): 。 2. A method for preparing the sterically hindered bis(arylamine) intermediate according to claim 1, characterized in that, This includes adding compound (A1), 4,4'-di-tert-butylbenzyl alcohol, to a thick-walled, pressure-resistant bottle. Rhenium heptaoxide and hexafluoroisopropanol are heated and stirred at 80°C for 12 hours to form an intermediate of formula (A2); formula (A1) is shown below: 。 3. A cyclic binuclear sterically hindered diimine ligand, as shown in formula (L): ； Where R is H or CHAr2; when R is CHAr2, Ar is... , or .

4. A method for preparing the cyclic binuclear sterically hindered diimine ligand as described in claim 3, characterized in that, include: The compound of formula (A1) and 2,3-butanedione were mixed in a 1:1 molar ratio, and 0.02 equivalents of p-toluenesulfonic acid were added. The mixture was refluxed at 120 °C for 48 hours in toluene as solvent to form a hydrogen-substituted ligand of formula (L). The intermediate of formula (A2) and 2,3-butanedione were mixed in a 1:1 molar ratio, and 0.02 equivalents of p-toluenesulfonic acid were added. The mixture was refluxed at 80°C for 48 hours with toluene as the solvent. Then, a water separator was added to the apparatus, and the mixture was refluxed at 120°C for 72 hours to form the CHAr2 substituted (L) ligand.

5. A cyclic binuclear sterically hindered nickel diimine complex, as shown in formula (Ni): ； Where R is H or CHAr2; when R is CHAr2, Ar is... , or .

6. A method for preparing the cyclic binuclear sterically hindered nickel diimine complex according to claim 5, characterized in that, The process includes the following steps: In an organic solvent, formula (L) reacts with nickel acetylacetonate and triphenylmethyltetra(pentafluorophenyl)borate to form a complex of formula (Ni).

7. The application of the cyclic binuclear sterically hindered nickel diimine complex of claim 5 as a catalyst for polymerization reactions.

8. The application according to claim 7, characterized in that, Application of cyclic binuclear sterically hindered nickel diimine complexes as catalysts in the polymerization of polyethylene compounds.

9. A method for preparing a polyethylene compound, characterized in that, Using the cyclic binuclear sterically hindered nickel diimine complex of formula (Ni) as a catalyst, ethylene is catalytically polymerized to obtain a polyethylene compound with a molecular weight of 5.7–15.9 × 10⁻⁶. 5 g / mol, branching degree of 22-49, melting point of 73-100℃; preferably, the method further includes using diethylaluminum chloride as a co-catalyst.

10. A method for preparing ethylene copolymers, characterized in that, Using the cyclic binuclear sterically hindered nickel diimine complex of formula (Ni) as a catalyst, ethylene and methyl 10-undecenoate were catalytically polymerized to obtain an ethylene copolymer with a molecular weight of 6.8–31.7 × 10⁻⁶. 4 g / mol, branching degree 12–31, melting point 110–120℃.

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