A nitro-substituted pyridine imine nickel (II) catalyst for the preparation of linear low density polyethylene

Abstract

The application discloses a nitro-substituted pyridine imine nickel (II) catalyst for preparing linear low-density polyethylene. The nitro-substituted pyridine imine nickel (II) catalyst has multiple catalytic active centers, can realize the regulation of polymer molecular weight by changing ligand structure and polymerization conditions, and has the advantages of high catalytic activity, low cost and stable performance. When the metal nickel complex is used for catalyzing ethylene polymerization, very good catalytic activity is shown, and low-density linear polyethylene products with low to wide molecular weight distribution are obtained. 13 CNMR spectrum shows that the obtained linear low-density polyethylene product has a large number of uniformly distributed long-chain branches (LCB), and the internal ethylene group is the main chain unsaturated group, which shows that the polymer has great industrial application potential.

Description

Technical Field

[0001] This invention relates to a nitro-substituted pyridineimine nickel (II) catalyst for the preparation of linear low-density polyethylene, belonging to the field of polyolefin catalysts. Background Technology

[0002] For many years, Brookhart-type nickel / palladium catalyst systems have attracted considerable attention due to their ability to efficiently produce polyethylene (PEs). Typically, 2-(arylimine)pyridine nickel complex systems can use ethylene as the sole monomer to prepare branched polyethylene, while N,N-diarylimine nickel complexes can produce various types of industrially valuable polyethylene products, including ultra-high molecular weight polyethylene (UHMWPE), linear low-density polyethylene (LLDPE), and polyethylene with molecular weights in the range of both.

[0003] Traditional linear low-density polyethylene (LLDPE) is a type of polyolefin product with very short comonomer branches, produced using ZN or Phillips-type transition metal catalysts, with ethylene as the main raw material and a small amount of α-olefins (such as 1-butene, 1-octene, etc.) as comonomers. On the one hand, the high cost of comonomers limits the economic viability of LLDPE applications; on the other hand, the high crystallinity of traditional LLDPE significantly reduces the turbidity and gloss of its film products. Therefore, it is essential to design and synthesize a more economical and practical catalyst for the preparation of LLDPE.

[0004] The inventors' research group and other research teams have been dedicated to designing N,N-nickel complex structures for the preparation of α-olefins and various novel polyethylene products. Their research has found that by reducing the steric hindrance of the N-aryl ortho-substituents, short-chain oligomers (C4, C6, etc.) can be mainly obtained, as shown in Formula 1 (ChemistryOpen, 2015, 4, 328–334). Furthermore, introducing electron-withdrawing NO2 groups into ligand frameworks with significant steric hindrance not only improves the catalytic activity of nickel catalysts but also significantly increases the molecular weight of the resulting polymers, as shown in Formula 2 (Dalton Trans., 2017, 46, 6934–6947). In addition, the design of the ligand structure and the setting of reaction conditions (such as temperature, pressure, and co-catalyst) can effectively control the branching structure of polyethylene.

[0005]

[0006] For 2-(arylimine)pyridine complexes, high-value-added polyethylenes with low to high branching can be obtained. For example, the introduction of a sterically large diphenylmethyl group of formula 3 (Dalton Trans., 2012, 41, 11999 – 12010) at the ortho and para positions of the N-aryl group exhibits high catalytic activity [>10] 7 g PE (mol Ni) -1 h -1 Furthermore, it can produce moderately branched polyethylene with a narrow molecular weight distribution. In summary, after structural modification (introducing strong electron-withdrawing groups), this catalytic system has the potential to produce linear low-density polyethylene (LLDPE) products containing a small amount of long-chain branches.

[0007] Furthermore, the most common drawback of 2-(arylimine)pyridine nickel complex catalysts is that the N-aryl group on one side provides limited steric protection to the active site, making them prone to deactivation at higher polymerization temperatures. This results in the production of polyethylene products with undesirable properties (e.g., low molecular weight and low melting temperature) with lower catalytic activity.

[0008] Therefore, the catalytic performance of the above-mentioned 2-(arylimine)pyridine nickel complex system, as well as the conditions and efficiency of its preparation method, still need further improvement. Based on this, it is also essential to further improve the structure of the 2-(arylimine)pyridine nickel complex and develop novel catalysts for the efficient preparation of linear low-density polyethylene. Summary of the Invention

[0009] The purpose of this invention is to provide a pyridineimine nickel complex containing nitro groups, which exhibits excellent catalytic activity in ethylene polymerization and can produce low-density linear polyethylene products with a wide molecular weight distribution.

[0010] The present invention first provides an intermediate of a pyridineimine nickel complex containing a nitro group as shown in formula (II):

[0011]

[0012] Equation (II) In the formula, R 1 They may be the same or different, each independently selected from alkyl groups containing 1 to 6 carbon atoms or diphenylmethyl groups containing substituents selected from H, F, Cl and OCH3; R 2 It is H or nitro; R 3 It is H, nitro, or diphenylmethyl containing a substituent, wherein the substituent is selected from H, F, Cl, and OCH3.

[0013] The structure of the intermediate is shown in formula (II-1), formula (II-2), formula (II-3), formula (II-4), or formula (II-5):

[0014] In equation (Ⅱ-1), (L1), R 1 =i-Pr;R 2 =H;R 3 =NO2; In equation (Ⅱ-2), (L2), R 1 =Et;R 2 =H;R 3 =NO2; In equation (Ⅱ-3), (L3), R 1 =CHPh2;R 2 =H;R 3 =NO2; In equation (Ⅱ-4), (L4), R 1 =CH(4-FPh)2;R 2 =H;R 3 =NO2; In equation (Ⅱ-5), (L5), R 1 =i-Pr;R 2 =NO2;R 3 =CH(4-FPh)2.

[0015] The intermediate of the present invention is prepared by the following method: The 2-acetylpyridine of formula (III) undergoes a condensation reaction with the aniline of formula (IV) to give the compound of formula (II);

[0016] In the formula, R 1 They may be the same or different, each independently selected from alkyl groups containing 1 to 6 carbon atoms or diphenylmethyl groups containing substituents selected from H, F, Cl and OCH3; R 2 It is H or nitro; R 3 It is H, nitro, or diphenylmethyl containing a substituent, wherein the substituent is selected from H, F, Cl, and OCH3; The condensation reaction was carried out under the catalysis of p-toluenesulfonic acid; The condensation reaction is carried out in an aromatic solvent; The condensation reaction was carried out under reflux conditions for 12 to 18 hours; The molar ratio of 2-acetylpyridine (III) to aniline (IV) is 1:1~2. The compound represented by formula (II) can be further purified by the following steps: a') Dissolve the compound of formula (II) obtained in the above steps in dichloromethane; b') Basic alumina was used for support, and column chromatography was performed on a basic alumina column. A mixed solvent of petroleum ether and ethyl acetate (preferably a volume ratio of 250:1) was used as the eluent. The eluted fraction was detected by thin-layer chromatography, and the second fraction was collected. c') Remove the solvent to obtain the purified compound shown in formula (II).

[0017] Based on the intermediate, the present invention further provides a pyridineimine nickel complex of formula (I) containing a nitro group:

[0018] Formula (I) In the formula, R 1 They may be the same or different, each independently selected from alkyl groups containing 1 to 6 carbon atoms or diphenylmethyl groups containing substituents selected from H, F, Cl and OCH3; R 2 It is H or nitro; R 3 It is H, nitro, or diphenylmethyl containing a substituent, wherein the substituent is selected from H, F, Cl, and OCH3.

[0019] The structure of the pyridineimine nickel complex is shown in formula (I-1), formula (I-2), formula (I-3), formula (I-4), or formula (I-5):

[0020] .

[0021] In equation (Ⅰ-1), (C1), R 1 =i-Pr;R 2 =H;R 3 =NO2; In equation (Ⅰ-2), (C2), R 1 =Et;R 2 =H;R 3 =NO2; In equation (Ⅰ-3), (C3), R 1 =CHPh2;R 2 =H;R 3 =NO2; In equation (Ⅰ-4), (C4), R 1 =CH(4-FPh)2;R 2 =H;R 3=NO2; In equation (Ⅰ-5), (C5), R 1 =i-Pr;R 2 =NO2;R 3 =CH(4-FPh)2.

[0022] The present invention further provides a method for preparing the pyridine imine nickel complex, comprising the following steps: The intermediate reacts with a nickel-containing compound to obtain the nickel complex shown in formula (I); The nickel-containing compound is a nickel-containing halide, such as (DME)NiBr2; The molar ratio of the nickel-containing compound to the intermediate is 1:1~2; The reaction temperature is 0~35℃; The reaction time is 8-24 hours; The reaction is carried out in a haloalkane or alcohol solvent, such as one or more of toluene, dichloromethane, ethanol, tetrahydrofuran, hexane or cyclohexane, more preferably a toluene solution; The nickel complex shown in formula (I) can be further purified by the following steps: a) Remove the solvent from the compound represented by formula (I) using a vacuum pump, and then dissolve it in an organic solvent (such as anhydrous diethyl ether); b) After precipitation, the solid and liquid phases are separated. The solid phase is washed with anhydrous diethyl ether and dried.

[0023] Based on the nickel pyridineimide complex, the present invention further provides a catalyst composition comprising a main catalyst and a co-catalyst; wherein the main catalyst is the nickel pyridineimide complex; The cocatalyst is selected from one or more of aluminoxane, alkylaluminum, and alkylaluminum chloride.

[0024] The aluminoxane is selected from at least one of methylaluminoxane and triisobutylaluminum-modified methylaluminoxane; The alkylaluminum chloride is selected from at least one of diethylaluminum chloride, ethylaluminum dichloride, and sesquiethylaluminum chloride; The molar ratio of metallic Al in the co-catalyst to the central metallic Ni in the pyridineimine nickel complex is 100~4000:1.

[0025] Preferably, when the cocatalyst is methylaluminoxane, the molar ratio of metal Al in the methylaluminoxane to the central metal Ni in the nickel complex of the pyridineimine nickel complex is 1000~4000:1, preferably 400~3000:1 or 2000:1; Preferably, when the co-catalyst is sesquiethylaluminum chloride (EASC), the molar ratio of metallic Al in the sesquiethylaluminum chloride to the central metallic Ni in the pyridineimine nickel complex is 100~1000:1, preferably 600:1; Preferably, when the co-catalyst is diethylaluminum chloride (Et2AlCl), the molar ratio of metallic Al in the diethylaluminum chloride (Et2AlCl) to the central metallic Ni in the pyridineimine nickel complex is 100~1000:1, more preferably the molar ratio is 400~800:1, 400:1, 500:1, 600:1 or 800:1; Preferably, when the cocatalyst is triisobutylaluminum-modified methylaluminoxane (MMAO), the molar ratio of metal Al in the triisobutylaluminum-modified methylaluminoxane to the central metal Ni in the pyridineimine nickel complex is 1000~4000:1, preferably 1250~2250:1, 1250:1, 1500:1, 2000:1 or 2250:1; Preferably, when the co-catalyst is ethylaluminum dichloride (EtAlCl2), the molar ratio of metallic Al in the ethylaluminum dichloride to the central metallic Ni in the pyridineimine nickel complex is 100~1000:1, preferably 400~800:1 or 600:1.

[0026] The application of the pyridineimine nickel complex and catalyst composition provided by this invention in the catalytic polymerization reaction of olefins to prepare polyolefins is also within the scope of protection of this invention.

[0027] Based on the catalyst composition, the present invention also provides a method for preparing polyethylene, comprising the following steps: Ethylene is obtained by polymerization under the catalysis of the catalyst composition. The polymerization reaction is carried out at a temperature of 20-60°C. C; The polymerization reaction takes 5 to 120 minutes; The polymerization reaction is carried out at a pressure of 1~10 atm; The solvent for the polymerization reaction is selected from one or more of toluene, dichloromethane, ethanol, tetrahydrofuran, hexane, and cyclohexane; The polymerization reaction was carried out in an ethylene atmosphere.

[0028] The present invention has the following beneficial effects: 1. This invention provides a method for preparing pyridineimine nickel complexes containing nitro groups and their intermediates. The preparation method has the advantages of mild reaction conditions, short cycle and simple operation conditions.

[0029] 2. This type of nickel complex has multiple catalytic active centers, and the molecular weight of the polymer can be controlled by changing the ligand structure and polymerization conditions. It also has the advantages of high catalytic activity, low cost and stable performance.

[0030] 3. The nickel complex provided by this invention exhibits excellent catalytic activity when used to catalyze ethylene polymerization, yielding low-density linear polyethylene products with a wide molecular weight distribution. For example, at 30... o Under C conditions, the activity of nickel complexes in catalyzing ethylene polymerization can reach as high as 4.7 × 10⁻⁶. 6 g·mol -1 (Ni)·h -1 The prepared polyethylene weight-average molecular weight M w In (2.6~137.7) kg·mol -1 The molecular weight fluctuates between 2.2 and 24.4, demonstrating a strong ability to regulate the molecular weight of polyethylene. 13 C10 NMR spectroscopy revealed that the obtained linear low-density polyethylene product had a large number of uniformly distributed long-chain branches (LCBs), with the internal vinyl groups being the most predominant unsaturated chain groups, demonstrating the great industrial application potential of this type of polymer. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the crystal structure of the coordination compound C3.

[0032] Figure 2 This is a schematic diagram of the crystal structure of the coordination compound C4.

[0033] Figure 3 This is a schematic diagram of the crystal structure of coordination compound C5.

[0034] Figure 4 The high-temperature 1H NMR spectrum of the polymer obtained in Example 14d is shown.

[0035] Figure 5 This is the high-temperature carbon NMR spectrum of the polymer obtained in Example 14d.

[0036] Figure 6 The high-temperature 1H NMR spectrum of the polymer obtained in Example 19a is shown.

[0037] Figure 7 This is the high-temperature carbon NMR spectrum of the polymer obtained in Example 19a. Detailed Implementation

[0038] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0039] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0040] Unless otherwise specified, all concentrations in the following examples are molar concentrations.

[0041] The molecular weight and molecular weight distribution of the polymers obtained in the following ethylene polymerization examples were determined by conventional high-temperature GPC method, the melting point was determined by conventional DSC method, and the polymerization activity of the polymers was calculated by the following formula: Polymer activity = Polymer yield / (Catalyst dosage · Polymerization time).

[0042] All the synthesized compounds described below were confirmed by NMR, IR and elemental analysis.

[0043] In a preferred embodiment, the synthesis of the complex in the following examples is carried out according to the following reaction equation:

[0044] Example 1 The preparation of (2,6-diisopropyl-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine [L1] as shown in formula (II), wherein R 1 It is isopropyl, R 2 For hydrogen, R 3 It is a nitro group.

[0045] A catalytic amount of p-toluenesulfonic acid was added to a toluene solution (50 mL) of 2-acetylpyridine (0.24 g, 2.0 mmol) and 2,6-diisopropyl-4-nitroaniline (0.49 g, 2.2 mmol), and the mixture was heated under reflux for 10 h. The solvent toluene was removed, and the residue was subjected to basic alumina column chromatography using a mixed solvent of petroleum ether and ethyl acetate (250:1 v / v). The eluent was detected by thin-layer silica gel chromatography, and the second fraction was collected. The solvent was removed to give a yellow solid. Yield: 79%.

[0046] The structural verification data is as follows: 1H NMR (400 Hz, CDCl3, TMS): δ 8.79–8.7.77 (d, J = 8.0 Hz, 1H, Py–H), 8.33–8.30 (d, J = 12.0 Hz, 1H, Py–H), 8.06 (s, 2H, Ar–H), 7.87–7.82 (t, J =10.0 Hz, 1H, Py–H), 7.46–7.42 (t, J = 8.0 Hz, 1H, Ar–H), 2.84–2.71 (s, 2H, –CH–), 2.23 (s, 3H, –CH3), 1.22–1.16 (m, 12H, –CH3). 13 C NMR (100 MHz, CDCl3, TMS): δ 162.8, 160.4, 150.7, 141.4, 138.2, 138.2, 130.6, 130.5, 129.4, 127.8, 123, 118.4, 115.3, 115.1, 49.3, 26.9,24.4, 20.8, 12.8, 12.6. FT-IR (cm –1 ): 2962 (m), 2929 (w), 2870 (w), 1652 ( v (C=N), m), 1583(m), 1567 (w), 1511 (s), 1464 (m), 1434 (m), 1363 (s), 1342 (s), 1323 (s),1302 (s), 1257 (s), 1240 (s), 1201 (m), 1148 (w), 1101 (s), 1045 (w), 993 (w), 965 (w), 901 (w), 808 (w), 785 (m), 756 (m), 746 (m), 720 (m). Elemental analysis: C 19 H 23 Theoretical values ​​for N3O2 (325.41): 70.13, 7.12; N, 12.91. Experimental values: C, 69.78; H, 7.13; N, 12.79. Example 2 The preparation of (2,6-diethyl-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine [L2] as shown in formula (II), wherein R 1 For ethyl, R2 For hydrogen, R 3 It is a nitro group.

[0047] A catalytic amount of p-toluenesulfonic acid was added to a 50 mL solution of 2-acetylpyridine (0.24 g, 2.0 mmol) and 2,6-diethyl-4-nitroaniline (0.43 g, 2.2 mmol) in toluene, and the mixture was heated under reflux for 10 h. The solvent toluene was removed, and the residue was subjected to alkaline alumina column chromatography using a mixture of petroleum ether and ethyl acetate in a volume ratio of 250:1. The eluent was detected by thin-layer silica gel chromatography, and the second fraction was collected. The solvent was removed to give a yellow solid. Yield: 83%.

[0048] The structural verification data is as follows: 1 H NMR (400 MHz, CDCl3, TMS): δ 8.69–8.68 (d, J = 4.0 Hz, 1H, Py–H), 8.32–8.30 (d, J = 8.0 Hz, 1H, Py–H), 8.02 (s, 2H, Ar–H), 7.85–7.81 (t, J =8.0 Hz, 1H, Py–H), 7.44–7.40 (t, J = 8.0 Hz, 1H, Py–H), 2.49–2.35 (m, 4H, –CH2–), 2.21 (s, 3H, CH3), 1.21–1.17 (m, 6H, CH3). 13 C NMR (100 MHz, CDCl3, TMS): δ 166.4, 154.4, 152.9, 147.8, 143.0,135.6, 131.4, 124.4, 120.6, 120.4, 23.5, 16.5, 12.0. FT-IR (cm –1 ): 3052 (w), 2964 (w), 2933 (w), 2872 (w), 1652 ( v (C=N),m), 1584 (m), 1505 (s), 1460 (m), 1434 (m), 1365 (m), 1334 (s), 1301 (m), 1259 (s), 1242 (m), 1204 (m), 1096 (s), 1040 (m), 879 (m), 799 (s), 780 (s), 741 (s), 710 (s). Elemental analysis: C 17H 19 Theoretical values ​​for N3O2 (297.36): C, 68.67; H, 6.44; N, 14.13. Experimental values: C, 69.03; H, 6.44; N, 13.88. Example 3 The preparation of (2,6-bis(difluorobenzyl)-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine [L3] as shown in formula (II), wherein R 1 It is diphenylmethyl, R 2 For hydrogen, R 3 It is a nitro group.

[0049] A catalytic amount of p-toluenesulfonic acid was added to a toluene (50 mL) solution of 2-acetylpyridine (0.24 g, 2.0 mmol) and 2,6-bis(difluorobenzyl)-4-nitroaniline (1.03 g, 2.2 mmol), and the mixture was heated under reflux for 10 h. The solvent toluene was removed, and the residue was subjected to basic alumina column chromatography using a mixture of petroleum ether and ethyl acetate in a volume ratio of 250:1. The eluent was detected by thin-layer silica gel chromatography, and the second fraction was collected. The solvent was removed to give a yellow solid. Yield: 65%.

[0050] The structural verification data is as follows: 1 H NMR (400 MHz, CDCl3, TMS): δ 8.62–8.60 (d, J = 8.0 Hz, 1H, Py–H), 7.98–7.96 (d, J = 8.0 Hz, 1H, Py–H) 7.78–7.73 (m, 2H, Py–H), 7.40–7.37 (t, J= 6.0 Hz, 1H, Ar–H), 7.28–7.19 (m, 8H, Ar–H), 7.02–6.97 (m, 8H, Ar–H), 5.30 (s, 2H, –CH–), 1.00 (s, 3H, –CH3). 13 C NMR (100 MHz, CDCl3, TMS): δ 169.7, 154.7, 154.3, 142.0, 140.9,136.4, 134.0, 129.7, 129.3, 128.8, 128.5, 126.9, 126.8, 125.3, 123.6, 121.6,52.2, 17.6. FT-IR (cm –1): 3058 (w), 3025 (w), 1966 (w), 1658 ( v (C=N), m), 1581(w),1513 (s), 1493 (m), 1470 (w), 1448 (w), 1434 (w), 1363 (w), 1329 (s) 1297(m), 1262 (w), 1232 (m), 1151 (w), 1093 (m), 1027 (w), 996 (w), 970 (w), 917 (w), 870 (w), 787 (m), 767 (m), 740 (m), 698 (s). Elemental analysis: C 39 H 31 Theoretical values ​​for N3O2 (573.70): C, 81.50; H, 5.45; N, 7.32. Experimental values: C, 81.34; H, 5.26; N, 7.18. Example 4 The preparation of (2,6-bis(bis(4-fluorophenyl)methyl)-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine [L4] as shown in formula (II), wherein R 1 It is di(4-fluorophenyl)methyl, R 2 For hydrogen, R 3 It is a nitro group.

[0051] A catalytic amount of p-toluenesulfonic acid was added to a 50 mL solution of 2-acetylpyridine (0.24 g, 2.0 mmol) and 2,6-bis(bis(4-fluorophenyl)methyl)-4-nitroaniline (1.19 g, 2.2 mmol) in toluene, and the mixture was heated under reflux for 10 h. The solvent toluene was removed, and the residue was subjected to alkaline alumina column chromatography using a mixture of petroleum ether and ethyl acetate in a volume ratio of 250:1. The eluent was detected by thin-layer silica gel chromatography, and the second fraction was collected. The solvent was removed to give a yellow solid. Yield: 60%.

[0052] The structural verification data is as follows: 1 H NMR (400 MHz, CDCl3, TMS): δ 8.64–8.63 (s, J = 4.0 Hz, 1H, Py–H),7.94–7.92 (d, J = 8.0 Hz, 1H, Py–H), 7.79–7.75 (t, J = 8.0 Hz, 3H, Py–H), 7.43–7.40 (t,J = 6.0 Hz, 1H, Ar–H), 6.98–6.92 (m, 16H, Ar–H), 5.25 (s, 2H, –CH–), 1.18 (s, 3H, –CH3). 13 C NMR (100 MHz, CDCl3, TMS): δ 169.6, 163.0, 162.9, 160.5, 160.5, 154.4, 153.9, 149.0, 143.7, 137.4, 137.4, 136.5, 136.5, 136.5, 133.8, 131.0,130.9, 130.6, 130.5, 125.6, 123.5, 121.4,115.9, 115.7, 115.6, 115.3, 50.7,17.9. FT-IR (cm –1 ): 3044 (w), 3003 (w), 2925 (w), 1643 ( v (C N), m), 1602(m), 1582 (m), 1504 (s), 1465 (w), 1431 (w), 1364 (s), 1334 (w), 1300 (m),1217 (s), 1158 (s), 1096 (m), 1016 (w), 962 (w), 913 (w), 880 (w), 835 (s), 791 (m), 744 (m), 717 (m), 688 (m). Elemental analysis: C 39 H 27 F4N3O2(645.66) Theoretical values: C, 72.55; H, 4.22; N, 6.51. Experimental values: C, 71.85; H, 4.24; N, 6.33. Example 5 The preparation of (4-(di(4-fluorophenyl)methyl)-2,6-diisopropyl-3-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine [L5] as shown in formula (II), wherein R 1 It is isopropyl, R 2 It is nitro, R 3 It is di(4-fluorophenyl)methyl.

[0053] A catalytic amount of p-toluenesulfonic acid was added to a 50 mL solution of 2-acetylpyridine (0.24 g, 2.0 mmol) and 4-(di(4-fluorophenyl)methyl)-2,6-diisopropyl-3-nitroaniline (0.92 g, 2.2 mmol) in toluene, and the mixture was heated under reflux for 10 h. The solvent toluene was removed, and the residue was subjected to basic alumina column chromatography using a mixture of petroleum ether and ethyl acetate in a volume ratio of 250:1. The eluent was detected by thin-layer silica gel chromatography, and the second fraction was collected. The solvent was removed to give an orange solid. Yield: 39%.

[0054] The structural verification data is as follows: 1 H NMR (400 MHz, CDCl3, TMS): δ 8.69–8.68 (d, J = 4.0 Hz, 1H, Py–H),8.33–8.31 (d, J = 8.0 Hz, 1H, Py–H), 7.85–7.81 (t, J = 8.0 Hz, Ar–1H), 7.43–7.40(t, J = 6.0 Hz, 1H), 7.07–6.98 (m, 8H, Ar–H), 6.83 (s, 1H, Ar–H m ), 5.43 (s, 1H, –CH–), 2.88–2.85 (m, 1H, –CH–), 2.64–2.60 (m, 1H, –CH–), 2.25 (s, 3H, –CH3), 1.28–26 (d, J = 8.0 Hz, 3H, CH3), 1.09–1.07 (d, J = 8.0 Hz, 3H, CH3), 1.02–1.01(d, J = 4 Hz, 3H, –CH3), 0.96–0.94 (d, J = 8.0 Hz, 3H, CH3). 13C NMR (100 MHz, CDCl3, TMS): δ 168.6, 162.9, 160.5, 155.6, 150.1,148.8, 147.1, 138.0, 138.0, 136.6, 130.6, 130.5, 128.6, 126.2, 125.8, 125.2,121.4, 115.4,115.4, 115.2, 115.2, 49.7, 29.5, 27.8, 23.3, 21.9, 21.3, 19.1,18.2. FT-IR (cm –1 ): 3067 (w), 3089 (w), 2963 (w), 2925 (w), 2869 (w), 1650( v (C N), m), 1598 (m), 1567 (w), 1524 (s), 1503 (s), 1465 (m), 1444 (w), 1363 (s), 1302 (w), 1223 (s), 1197 (m), 1157 (m), 1101 (m), 1043 (w), 1014 (w), 967 (w), 896 (w), 823 (w), 784 (w), 741 (w), 673 (w). Elemental analysis: C 32 H 31 Br2F2N3O2(527.62) Theoretical values: C, 72.85; H, 5.92; N, 7.96. Experimental values: C, 72.50; H, 5.89; N, 7.87. Example 6 Prepare the [(2,6-diisopropyl-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine]nickel bromide(II) [complex C1] shown in formula (I), wherein R 1 It is isopropyl, R 2 For hydrogen, R 3 X is a nitro group and bromine is a bromine group.

[0055] At room temperature, (DME)NiBr2 (0.30 g, 0.98 mmol) and (2,6-diisopropyl-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine (0.36 g, 1.10 mmol) prepared in Example 1 were mixed and dissolved in a mixture of dichloromethane and ethanol. The mixture was stirred for 16 h under nitrogen protection. After removing dichloromethane under reduced pressure, diethyl ether was added, and a light green solid precipitated. The precipitate was filtered, washed with diethyl ether, and dried to obtain a light green solid. Yield: 91%. The structural verification data is as follows: FT-IR (cm –1 ): 2967 (w), 2927 m), 2872 (w), 1621 ( v (C N), w),1597 (w),1574 (w), 1514 (s), 1441 (m), 1376 (m), 1350 (m), 1322 (s), 1262 (m), 1192(w), 1168 (w), 1112 (m), 1075 (m), 1050 (w), 1022 (w), 937 (w), 912 (w), 839(w), 786 (s), 745 (m). Anal. Calcd. for C 19 H 23 Br2N3O2(543.91): C, 41.96; H, 4.26; N, 7.73. Found: C, 42.12; H, 4.64, N, 7.48. Elemental analysis: C 19 H 23 Br2N3O2 (543.91) Theoretical values: C, 41.96; H, 4.26; N, 7.73. Experimental values: C, 42.12; H, 4.64; N, 7.48. Example 7 Prepare the [(2,6-diethyl-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine]nickel bromide(II) [complex C2] shown in formula (I), wherein R 1 For ethyl, R 2 For hydrogen, R 3 X is a nitro group and bromine is a bromine group.

[0056] At room temperature, (DME)NiBr2 (0.30 g, 1.0 mmol) and (2,6-diethyl-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine (0.33 g, 1.1 mmol) prepared in Example 2 were mixed and dissolved in a mixture of dichloromethane and ethanol. The mixture was stirred for 16 h under nitrogen protection. After removing dichloromethane under reduced pressure, diethyl ether was added, resulting in the precipitation of a brown solid. The precipitate was filtered, washed with diethyl ether, and dried to obtain the brown solid. Yield: 91%. The structural verification data is as follows: FT-IR (cm –1 ): 3163 (w), 2976 (w), 1626 ( v (C N), m), 1592 (m), 1516(s), 1446 (m), 1320 (s), 1257 (s), 1193 (w), 1104 (w), 1054 (w), 1024 (w),897 (m), 841 (w), 778 (s), 744 (s). Elemental analysis: C 34 H 38 Br4N6Ni2O4 . 2H₂O (533.87) Theoretical values: C, 38.25; H, 3.96; N, 7.87. Experimental values: C, 37.86; H, 4.25; N, 7.58. Example 8 Prepare the nickel bromide (II) [complex C3] of formula (I) shown, wherein R 1 It is diphenylmethyl, R 2 For hydrogen, R 3 X is a nitro group and bromine is a bromine group.

[0057] At room temperature, (DME)NiBr2 (0.30 g, 1.0 mmol) and (2,6-bis(difluorobenzyl)-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine (0.63 g, 1.1 mmol) prepared in Example 3 were mixed and dissolved in a mixture of dichloromethane and ethanol. The mixture was stirred for 16 h under nitrogen protection. After removing dichloromethane under reduced pressure, diethyl ether was added, and a green solid precipitated. The precipitate was filtered, washed with diethyl ether, and dried to obtain the green solid. Yield: 56%. The structural verification data is as follows: FT-IR (cm –1): 3279 (w), 3028 (w), 1975 (w), 1621 ( v (C N), m), 1597(m), 1522 (s), 1494 (m), 1444 (m), 1398 (w), 1375 (w), 1334 (s), 1323 (m), 1257 (m), 1187 (w), 1075 (w), 1033 (m), 916 (w), 874 (w), 819 (w), 797 (w),767 (m), 743 (m), 701 (s) 671 (m), 654 (m). Anal. Calcd. forC 120 H 115 N9Br6C l6 O 14 Ni3(2775.49): C, 51.93; H, 4.18; N, 4.54. Found: C, 51.74; H, 4.11; N, 4.36. Elemental analysis: C 120 H 115 N9Br6C l6 O 14 Ni3 (2775.49): Theoretical values: C, 51.93; H, 4.18; N, 4.54. Experimental values: C, 51.74; H, 4.11; N, 4.36. Crystal structure diagram as shown Figure 1 As shown, for clarity, all hydrogen atoms in the complex molecular structure are not drawn when using ORTEP to plot the diagram. It can be seen that the C3(H2O) crystal cell contains two independent molecules (a and b), which are essentially identical, differing only in the positions of the ligand N, the water of crystallization within the N cavity, and the (DME)NiBr2 unit.

[0058] Example 9 Prepare the nickel bromide (II) [complex C4] of formula (I) shown, wherein R 1 It is di(4-fluorophenyl)methyl, R 2 For hydrogen, R 3 X is a nitro group and bromine is a bromine group.

[0059] At room temperature, (DME)NiBr2 (0.30 g, 1.0 mmol) and (2,6-bis(bis(4-fluorophenyl)methyl)-4-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine (0.71 g, 1.1 mmol) prepared in Example 4 were mixed and dissolved in a mixture of dichloromethane and ethanol. The mixture was stirred for 16 h under nitrogen protection. After removing dichloromethane under reduced pressure, diethyl ether was added, resulting in the precipitation of a brown solid. The precipitate was filtered, washed with diethyl ether, and dried to obtain the brown solid. Yield: 80%. The structural verification data is as follows: FT-IR (cm –1 ): 3317 (w), 3079 (w), 2911 (w), 1598 ( v (C N), m), 1505(s), 1438 (w), 1343 (m), 1317 (m), 1224 (s), 1158 (s), 1098 (w), 1019 (w),914 (w), 881 (w), 839 (s), 980 (m), 740 (w), 669(w). Elemental analysis: C 39 H 27 Br2F4N3NiO2 (864.16) Theoretical values: C, 54.21; H, 3.5; N, 4.86. Experimental values: C, 54.04; H, 3.25; N, 4.57. Crystal structure diagram as shown Figure 2 As shown, the solid structure of C4 is a centrosymmetric dimer. The bond lengths (Ni1–N1) between nickel atoms and pyridine nitrogen atoms are not significantly different from those between imine nitrogen atoms (Ni1–N2), which means that the pyridine ring and imine nitrogen atoms have similar coordination with the nickel metal center.

[0060] Example 10 Prepare the nickel bromide (II) [complex C5] of formula (I) shown, wherein R 1 It is isopropyl, R 2 It is nitro, R 3 X is bis(4-fluorophenyl)methyl, and X is bromine.

[0061] At room temperature, (DME)NiBr2 (0.30 g, 1.0 mmol) and (4-(di(4-fluorophenyl)methyl)-2,6-diisopropyl-3-nitrophenyl)-1-(pyridin-2-yl)ethane-1-imine (0.58 g, 1.1 mmol) prepared in Example 5 were mixed and dissolved in a mixture of dichloromethane and ethanol. The mixture was stirred for 16 h under nitrogen protection. After removing dichloromethane under reduced pressure, diethyl ether was added, resulting in the precipitation of a brown solid. The solid was filtered, washed with diethyl ether, and dried to obtain a brown solid. Yield: 94%. The structural verification data is as follows: FT-IR (cm –1 ): 2978 (w), 2935 (w), 1618 ( v (C N), m), 1593 (w), 1536(w), 1504 (s), 1464 (w), 1445 (w), 1372 (m), 1328 (w), 1319 (w) 1261 (w),1218 (s), 1189 (w), 1159 (m), 1128 (w), 1094 (w), 1049 (w), 1024 (w), 957(w), 917 (w), 865 (w), 846 (m), 823 (m), 775 (m), 743 (w), 709 (w), 653 (w). Elemental analysis: C 32 H 31 Br2F2N3NiO2(746.13) Theoretical values: C, 51.65; H, 4.20; N, 7.53. Experimental values: C, 51.72; H, 4.31; N, 7.39. Crystal structure diagram as shown Figure 3 As shown, the solid structure of C5 is similar to that of C4, both exhibiting centrosymmetric dimers. The difference lies in the substituents on the imine aromatic ring: C4 has 2,6-di(di(4-fluorophenyl)methyl); C5 has 2,6-diisopropyl. Furthermore, possibly because the C4 complex contains a more sterically hindered substituent (di(4-fluorophenyl)methyl), the distances between the nickel atom and the two nitrogen atoms (Ni1–N1 and Ni1–N2) in the C4 complex are significantly greater than those in the C6 complex.

[0062] Example 11 Ethylene polymerization at 10 atm using C4 complex and MAO co-catalyst: Under an ethylene atmosphere, 20 mL of toluene, 30 mL of a toluene solution containing 2 µmol of catalyst C4, 2.7 mL of a 1.46 mol / L toluene solution containing co-catalyst MAO, and 50 mL of toluene were sequentially added to a 250 mL stainless steel autoclave. At this point, the Al / Ni ratio was 2000:1. Mechanical stirring was initiated and maintained at 400 rpm. When the polymerization temperature reached 30 °C, ethylene was introduced into the reactor, and the polymerization reaction began. The ethylene pressure was maintained at 10 atm at 30 °C, and stirring was continued for 30 min. The reaction solution was neutralized with an ethanol solution acidified with 5% hydrochloric acid to obtain a polymer precipitate. The precipitate was washed several times with ethanol, vacuum dried to constant weight, and weighed.

[0063] Polymerization activity: 1.9 × 10 6 g·mol -1 (Ni)·h -1 Polymer T m =67.8, 121.4 °C (T) m (M is the melting temperature of the polymer, obtained by DSC testing), and the polymer molecular weight M. w =78.9 kg·mol -1 PDI = 21.6 (M) w (This represents the weight-average molecular weight of the polymer, obtained through heated GPC testing).

[0064] Example 12 Ethylene polymerization under pressure using C4 complex and EASC co-catalyst: Under an ethylene atmosphere, 20 mL of toluene, 30 mL of a toluene solution containing 2 µmol of catalyst C4, 1.4 mL of a 0.87 mol / L toluene solution containing co-catalyst EASC, and 50 mL of toluene were sequentially added to a 250 mL stainless steel autoclave. At this point, the Al / Ni ratio was 600:1. Mechanical stirring was initiated and maintained at 400 rpm. When the polymerization temperature reached 30 °C, ethylene was introduced into the reactor, and the polymerization reaction began. The ethylene pressure was maintained at 10 atm at 30 °C, and stirring was continued for 30 min. The reaction solution was neutralized with an ethanol solution acidified with 5% hydrochloric acid to obtain a polymer precipitate. The precipitate was washed several times with ethanol, vacuum dried to constant weight, and weighed.

[0065] Polymerization activity: 1.8 × 10 6 g·mol -1 (Ni)·h -1 Polymer T m = 118.8 °C (T m (M is the melting temperature of the polymer, obtained by DSC testing), and the polymer molecular weight M. w = 130.4 kg·mol -1PDI = 28.5 (M w (This represents the weight-average molecular weight of the polymer, obtained through heated GPC testing).

[0066] Example 13 Ethylene polymerization under pressure using C4 complex and Et2AlCl as co-catalysts: Under an ethylene atmosphere, 20 mL of toluene, 30 mL of a toluene solution containing 2 µmol of catalyst C4, 1.0 mL of a co-catalyst Et2AlCl (1.17 mol / L heptane solution), and 50 mL of toluene were sequentially added to a 250 mL stainless steel autoclave. At this point, the Al / Ni ratio was 600:1. Mechanical stirring was initiated and maintained at 400 rpm. When the polymerization temperature reached 30 °C, ethylene was introduced into the reactor, and the polymerization reaction began. The ethylene pressure was maintained at 10 atm at 30 °C, and stirring was continued for 30 min. The reaction solution was neutralized with an ethanol solution acidified with 5% hydrochloric acid to obtain a polymer precipitate. The precipitate was washed several times with ethanol, vacuum dried to constant weight, and weighed.

[0067] Polymerization activity: 0.2 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 125.3 °C (T m (M is the melting temperature of the polymer, obtained by DSC testing), and the polymer molecular weight M. w = 63.2 kg·mol -1 PDI = 14.5 (M w (This represents the weight-average molecular weight of the polymer, obtained through heated GPC testing).

[0068] Example 14: Ethylene polymerization under pressure using complex C4 and MMAO co-catalyst: a) Under an ethylene atmosphere, 20 mL of toluene, 30 mL of a toluene solution containing 2 µmol of catalyst C4, 2.1 mL of a 1.93 mol / L toluene solution containing co-catalyst MMAO, and 50 mL of toluene were sequentially added to a 250 mL stainless steel autoclave. At this point, the Al / Ni ratio was 2000:1. Mechanical stirring was initiated and maintained at 400 rpm. When the polymerization temperature reached 30 °C, ethylene was introduced into the reactor, and the polymerization reaction began. The ethylene pressure was maintained at 10 atm at 30 °C, and stirring was continued for 30 min. The reaction solution was neutralized with an ethanol solution acidified with 5% hydrochloric acid to obtain a polymer precipitate. The precipitate was washed several times with ethanol, dried under vacuum to constant weight, and weighed.

[0069] Polymerization activity: 2.1 × 10⁻⁶ 6 g·mol-1 (Ni)·h -1 Polymer T m = 93.4, 110.6 °C (T m (M is the melting temperature of the polymer, obtained by DSC testing), and the polymer molecular weight M. w = 7.2 kg·mol -1 PDI = 3.4 (M w (This represents the weight-average molecular weight of the polymer, obtained through heated GPC testing).

[0070] b) is basically the same as a), except that the amount of co-catalyst used is 1.3 mL of MMAO (1.93 mol / L toluene solution), making the Al / Ni ratio 1250:1. Polymerization activity: 1.6 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 84.8, 114.4°C, M w = 8.2 kg·mol -1 PDI = 4.1.

[0071] c) is basically the same as a), except that the co-catalyst used is 1.6 mL of MMAO (1.93 mol / L toluene solution), making the Al / Ni ratio 1500:1. Polymerization activity: 2.0 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 91.8, 113.3°C, M w = 10.1 kg·mol -1 PDI = 4.5.

[0072] d) Basically the same as a), except that: 1.8 mL of MMAO (1.93 mol / L toluene solution) is used as the co-catalyst, resulting in an Al / Ni ratio of 1750:1. Polymerization activity: 2.4 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 84.8, 114.5°C, M w =8.5 kg·mol -1 PDI = 5.1.

[0073] Take 100 mg of the obtained polymer, dissolve it in 5 mL of deuterated tetrachloroethane, and test the polymer at 30 °C. 1 H and13 C data. Signal accumulation at 64 and 2000 times yielded peak shifts between 0-6 and 10-40 (ppm), respectively, indicating shifts in hydrogen atoms on double bonds, the main chain, and branches. This confirms that the obtained polymer is unsaturated polyethylene with a small amount of branching (see details). Figure 4 and Figure 5 ).

[0074] e) is basically the same as a), except that 2.3 mL of MMAO (1.93 mol / L toluene solution) is used as the co-catalyst, resulting in an Al / Ni ratio of 2250:1. Polymerization activity: 1.6 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 86.9, 114.1°C, M w =6.0 kg·mol -1 PDI = 2.9.

[0075] f) is basically the same as d), except that the polymerization temperature is 20 °C. Polymerization activity: 1.2 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m =101.5, 114.0 °C, M w =21.6 kg·mol -1 PDI = 8.9.

[0076] g) is basically the same as d), except that the polymerization temperature is 40 °C. Polymerization activity: 2.2 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 76.4, 115.4 °C, M w =7.6 kg·mol -1 PDI = 5.5.

[0077] h) is basically the same as d), except that the polymerization temperature is 50 °C. Polymerization activity: 0.9 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 61.1, 119.8 °C, M w =3.9 kg·mol -1 PDI = 4.2.

[0078] i) Basically the same as d), except that the polymerization time is 10 min. Polymerization activity: 1.6 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 82.3, 113.9 °C, M w =6.2 kg·mol -1 PDI = 3.3.

[0079] j) is basically the same as d), except that the polymerization time is 20 min. Polymerization activity: 1.7 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 85.5, 113.1 °C, M w =6.5 kg·mol -1 PDI = 3.4.

[0080] k) is basically the same as d), except that the polymerization time is 40 min. Polymerization activity: 1.9 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 93.9, 112.3 °C, M w =9.6 kg·mol -1 PDI = 4.3.

[0081] l) is basically the same as d), except that the polymerization time is 50 min. Polymerization activity: 1.8 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 92.3, 111.8 °C, M w =10.3 kg·mol -1 PDI = 5.5.

[0082] m) is basically the same as d), the difference being: polymerization time is 60 min. Polymerization activity: 1.6 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 95.1, 113.5 °C, M w =11.4 kg·mol -1 PDI = 5.3.

[0083] n) is basically the same as d), the difference being: polymerization pressure 5 atm. Polymerization activity: 0.8 × 10⁻⁶6 g·mol -1 (Ni)·h -1 Polymer T m = 70.9, 121.4 °C, M w =5.5 kg·mol -1 PDI = 2.8.

[0084] o) is basically the same as d), except that the polymerization pressure is 1 atm. There is no polymerization activity.

[0085] Example 15 Ethylene polymerization under pressure using complex C1 and MMAO co-catalyst: Basically the same as Example 14d), except that the main catalyst is C1. Polymerization activity: 0.7 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 85.3, 117.0 °C, M w =7.0 kg·mol -1 PDI = 5.0.

[0086] Example 16 Ethylene polymerization under pressure using complex C2 and MMAO co-catalyst: Basically the same as Example 14d), except that the main catalyst is C2. Polymerization activity: 2.7 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 82.9, 112.1 °C, M w =2.6 kg·mol -1 PDI = 2.4.

[0087] Example 17 Ethylene polymerization under pressure using complex C3 and MMAO co-catalyst: Basically the same as Example 14d), except that the main catalyst is C3. Polymerization activity: 1.5 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 90.2, 105.7 °C, M w =10.0 kg·mol -1 PDI = 3.7.

[0088] Example 18 Ethylene polymerization under pressure using C5 complex and MMAO co-catalyst: Basically the same as Example 14d), except that the main catalyst is C5. Polymerization activity: 1.0 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 69.0, 125.3 °C, M w =1.5 kg·mol -1 PDI = 7.2.

[0089] Example 19 Ethylene polymerization under pressure using complex C4 and EtAlCl2 as co-catalysts: a) Under an ethylene atmosphere, 20 mL of toluene, 30 mL of a toluene solution containing 2 µmol of catalyst C4, 0.6 mL of a co-catalyst EtAlCl2 (2.17 mol / L hexane solution), and 50 mL of toluene were sequentially added to a 250 mL stainless steel autoclave. At this point, the Al / Ni ratio was 600:1. Mechanical stirring was initiated and maintained at 400 rpm. When the polymerization temperature reached 30 °C, ethylene was introduced into the reactor, and the polymerization reaction began. The ethylene pressure was maintained at 10 atm at 30 °C, and stirring was continued for 30 min. The reaction solution was neutralized with an ethanol solution acidified with 5% hydrochloric acid to obtain a polymer precipitate. The precipitate was washed several times with ethanol, dried under vacuum to constant weight, and weighed.

[0090] Polymerization activity: 3.8 × 10 6 g·mol -1 (Ni)·h -1 Polymer T m = 125.9 °C. (T) m (M is the melting temperature of the polymer, obtained by DSC testing), and the polymer molecular weight M. w = 61.5 kg·mol -1 PDI = 12.9 (M w (This represents the mass-average molecular weight of the polymer, obtained through heated GPC testing).

[0091] Take 100 mg of the obtained polymer, dissolve it in 5 mL of deuterated tetrachloroethane, and test the polymer at 30 °C. 1 H and 13 C data. Signal accumulation at 64 and 2000 times yielded peak shifts between 0-6 and 10-40 (ppm), respectively, indicating shifts in hydrogen atoms on double bonds, the main chain, and branches. This confirms that the obtained polymer is unsaturated polyethylene with a small amount of branching (see details). Figure 6 and Figure 7 ).

[0092] b) is basically the same as a), except that the co-catalyst used is 0.4 mL of EtAlCl2 (2.17 mol / L hexane solution), making the Al / Ni ratio 400:1. Polymerization activity: 0.9 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 119.3 °C, M w = 129.5 kg·mol -1 PDI = 17.7.

[0093] c) is basically the same as a), except that the co-catalyst used is 0.5 mL of EtAlCl2 (2.17 mol / L hexane solution), making the Al / Ni ratio 500:1. Polymerization activity: 2.8 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 126.0 °C, M w = 137.7 kg·mol -1 PDI = 14.2.

[0094] d) Basically the same as a), except that: 0.6 mL of EtAlCl2 (2.17 mol / L hexane solution) is used as the co-catalyst, making the Al / Ni ratio 700:1. Polymerization activity: 3.2 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 123.3 °C, M w = 61.0 kg·mol -1 PDI = 7.6.

[0095] e) is basically the same as a), except that the co-catalyst used is 0.7 mL of EtAlCl2 (2.17 mol / L hexane solution), making the Al / Ni ratio 800:1. Polymerization activity: 3.1 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 122.4 °C, M w = 57.1 kg·mol -1 PDI = 8.3.

[0096] f) is basically the same as a), except that the polymerization temperature is 20 °C. Polymerization activity: 3.1 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 121.9 °C, M w =63.3 kg·mol -1 PDI = 9.9.

[0097] g) is basically the same as a), except that the polymerization temperature is 40 °C. Polymerization activity: 3.5 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 124.1 °C, M w =45.1 kg·mol -1 PDI = 16.8.

[0098] h) is basically the same as a), except that the polymerization temperature is 50 °C. Polymerization activity: 3.4 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 123.7 °C, M w =32.9 kg·mol -1 PDI = 18.2.

[0099] i) Basically the same as a), except that the polymerization temperature is 60 °C. Polymerization activity: 3.0 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 119.3 °C, M w =30.9 kg·mol -1 PDI = 20.5.

[0100] j) is basically the same as a), except that the polymerization time is 10 min. Polymerization activity: 2.7 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 124.5 °C, M w =53.0 kg·mol -1 PDI = 2.2.

[0101] k) is basically the same as a), except that the polymerization time is 20 min. Polymerization activity: 2.9 × 10⁻⁶ 6 g·mol-1 (Ni)·h -1 Polymer T m =121.9 °C, M w =56.3 kg·mol -1 PDI = 6.5.

[0102] l) is basically the same as a), except that the polymerization time is 40 min. Polymerization activity: 3.7 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m =124.5 °C, M w =67.3 kg·mol -1 PDI = 13.3.

[0103] m) is basically the same as a), except that the polymerization time is 50 min. Polymerization activity: 3.5 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m =124.8 °C, M w =69.6 kg·mol -1 PDI = 12.9.

[0104] n) is basically the same as a), except that the polymerization time is 60 min. Polymerization activity: 3.1 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m =124.6 °C, M w =81.6 kg·mol -1 PDI = 24.4.

[0105] o) is basically the same as a), except that the polymerization pressure is 5 atm. Polymerization activity: 2.1 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m = 124.0 °C, M w =32.2 kg·mol -1 PDI = 5.6.

[0106] p) is basically the same as a), except that the polymerization pressure is 1 atm. There is no polymerization activity.

[0107] Example 20 Ethylene polymerization under pressure using complex C1 and EtAlCl2 as co-catalysts: Basically the same as Example 19a), except that the main catalyst is C1. Polymerization activity: 3.1 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m =118.6 °C, M w =13.1 kg·mol -1 PDI = 12.7.

[0108] Example 21 Ethylene polymerization under pressure using complex C2 and EtAlCl2 as co-catalysts: Basically the same as Example 19a), except that the main catalyst is C2. Polymerization activity: 4.7 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m =117.8°C, M w =22.5 kg·mol -1 PDI=7.9.

[0109] Example 22 Ethylene polymerization under pressure using complex C3 and EtAlCl2 as co-catalysts: Basically the same as Example 19a), except that the main catalyst is C3. Polymerization activity: 2.6 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m =123.2 °C, M w =7.4 kg·mol -1 PDI=8.9.

[0110] Example 23 Ethylene polymerization under pressure using complex C5 and EtAlCl2 as co-catalysts: Basically the same as Example 19a), except that the main catalyst is C5. Polymerization activity: 4.6 × 10⁻⁶ 6 g·mol -1 (Ni)·h -1 Polymer T m =120.3 °C, M w =23.3 kg·mol -1 PDI=22.2.

Claims

1. The pyridineimine nickel complex containing a nitro group shown in formula (I): Formula (I) In the formula, R 1 The same, selected from alkyl groups having 1 to 6 carbon atoms or diphenylmethyl groups containing substituents, wherein the substituents are selected from H, F, Cl and OCH3; R 2 It is H or nitro; R 3 It is H, nitro, or diphenylmethyl containing a substituent, wherein the substituent is selected from H, F, Cl, and OCH3; R 2 R 3 They may be the same or different, one of which is nitro.

2. The pyridineimine nickel complex according to claim 1, characterized in that: The structure of the pyridineimine nickel complex is shown in formula (I-1), formula (I-2), formula (I-3), formula (I-4), or formula (I-5): 。 3. A method for preparing the pyridineimine nickel complex according to claim 1 or 2, comprising the following steps: The intermediate reacts with a nickel-containing compound to obtain the nickel complex shown in formula (I); The nickel-containing compound is a nickel-containing halide; The molar ratio of the nickel-containing compound to the intermediate is 1:1~2; The reaction temperature is 0~35℃; The reaction time is 8-24 hours; The reaction is carried out in a haloalkane or alcohol solvent; The intermediate is a pyridineimine nickel complex containing a nitro group, as shown in formula (II): Equation (II) In the formula, R 1 The same, selected from alkyl groups having 1 to 6 carbon atoms or diphenylmethyl groups containing substituents, wherein the substituents are selected from H, F, Cl and OCH3; R 2 It is H or nitro; R 3 It is H, nitro, or diphenylmethyl containing a substituent, wherein the substituent is selected from H, F, Cl, and OCH3; R 2 R 3 They may be the same or different, one of which is nitro.

4. The preparation method according to claim 3, characterized in that: The structure of the intermediate is shown in formula (II-1), formula (II-2), formula (II-3), formula (II-4), or formula (II-5): 。 5. The preparation method according to claim 4, comprising the following steps: the intermediate is prepared according to the following method: The 2-acetylpyridine of formula (III) undergoes a condensation reaction with the aniline of formula (IV) to give the compound of formula (II); In the formula, R 1 The same, selected from alkyl groups having 1 to 6 carbon atoms or diphenylmethyl groups containing substituents, wherein the substituents are selected from H, F, Cl and OCH3; R 2 It is H or nitro; R 3 It is H, nitro, or diphenylmethyl containing a substituent, wherein the substituent is selected from H, F, Cl, and OCH3; The condensation reaction was carried out under the catalysis of p-toluenesulfonic acid; The condensation reaction is carried out in an aromatic solvent; The condensation reaction was carried out under reflux conditions for 12 to 18 hours; The molar ratio of 2-acetylpyridine (as shown in formula (III)) to aniline (as shown in formula (IV)) is 1:1~2.

6. A catalyst composition comprising a main catalyst and a co-catalyst; wherein, The main catalyst is the pyridineimine nickel complex containing nitro groups as described in claim 1 or 2; The cocatalyst is selected from one or more of aluminoxane, alkylaluminum, and alkylaluminum chloride. The aluminoxane is selected from at least one of methylaluminoxane and triisobutylaluminum-modified methylaluminoxane; The alkylaluminum chloride is selected from at least one of diethylaluminum chloride, ethylaluminum dichloride, and sesquiethylaluminum chloride; The molar ratio of metal Al in the co-catalyst to the central metal Ni in the nitro-containing pyridineimine nickel complex is 100~4000:

1.

7. The catalyst composition according to claim 6, characterized in that: When the cocatalyst is methylaluminoxane, the molar ratio of metal Al in the methylaluminoxane to the central metal Ni in the nickel complex of the pyridineimine nickel complex containing nitro groups is 1000~4000:1; When the co-catalyst is sesquiethylaluminum chloride, the molar ratio of metallic Al in the sesquiethylaluminum chloride to the central metallic Ni in the pyridineimine nickel complex is 100~1000:1; When the co-catalyst is diethylaluminum chloride, the molar ratio of metallic Al in the diethylaluminum chloride to the central metallic Ni in the pyridineimine nickel complex is 100~1000:1; When the cocatalyst is triisobutylaluminum-modified methylaluminoxane, the molar ratio of metal Al in the triisobutylaluminum-modified methylaluminoxane to the central metal Ni in the pyridineimine nickel complex is 1000~4000:1; When the cocatalyst is ethylaluminum dichloride, the molar ratio of metallic Al in the ethylaluminum dichloride to the central metallic Ni in the pyridineimine nickel complex is 100~1000:

1.

8. A method for preparing polyethylene, comprising the following steps: Ethylene is obtained by polymerization under the catalysis of the catalyst composition of claim 6 or 7; The polymerization reaction is carried out at a temperature of 20~60℃; The polymerization reaction takes 5 to 120 minutes; The polymerization reaction is carried out at a pressure of 5-10 atm. The solvent for the polymerization reaction is selected from one or more of toluene, dichloromethane, ethanol, tetrahydrofuran, hexane, and cyclohexane; The polymerization reaction was carried out in an ethylene atmosphere.

9. The use of the pyridineimine nickel complex of claim 1 or 2, or the catalyst composition of claim 6 or 7, in the catalytic polymerization of olefins to prepare polyolefins.

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