Synthesis and application of asymmetric alpha-diimine nickel catalyst containing pyridine

Abstract

The invention discloses synthesis and application of a pyridine-containing asymmetric alpha-diimine nickel catalyst and application of Lewis acid regulation in olefin polymerization, and belongs to the technical field of olefin polymerization. In the olefin polymerization reaction catalyzed by the diimine nickel catalyst, the Lewis acid plays a very ingenious role of a regulator, and the electronic property and space environment of the active center of the catalyst are changed by introducing the Lewis acid salt, so that the dual regulation of the steric hindrance and the electronic effect of the catalyst is realized; the performance of the catalyst is improved; and the structure of the final polymer is changed. Compared with known alpha-diimine nickel catalysts, the alpha-diimine nickel catalyst has the advantages of high polymerization activity, strong thermal stability and improvement of monomer insertion rate.

Description

Technical Field

[0001] This invention belongs to the field of olefin polymerization technology, specifically the preparation and synthesis of a pyridine-containing asymmetric α-diimine nickel catalyst, and the application of Lewis acid regulation in olefin polymerization. Background Technology

[0002] With global economic development, polyolefin materials have become indispensable cornerstone materials in modern industry and society, widely used in packaging, building materials, agriculture, automobiles, medical and high-tech fields, holding a comprehensive and irreplaceable position. Accompanying the industrialization and consumption upgrade of emerging economies, the demand for novel polyolefin materials continues to grow, making breakthroughs and diversification of olefin catalysts crucial. In 1995, Maurice Brookhart's group at the University of North Carolina first reported a cationic α-diimine nickel(II) catalyst (Johnson, LK; Killian, CK; Brookhart MS J Am. Chem. Soc. 1995, 117, 6414.). This pioneering work brought significant attention to post-transition metal catalysts. Researchers have developed more sophisticated strategies to overcome the bottlenecks of early catalysts, especially in thermal stability and polymer structure control, such as N-aryl modification and framework structure modification to regulate steric hindrance and electronic effects of ligands, thereby improving catalyst performance and the structure and properties of polymerization products.

[0003] Sun et al. designed and synthesized a series of asymmetric ligands containing sterically hindered aromatic amines (Catalysisence & Technology, 2013, 3(10): 2737-2745). Under the action of MAO and MMAO, these polymers exhibited high activity in ethylene polymerization. Compared with traditional Brookhart-type catalysts, these catalysts showed superior thermal stability and catalytic activity, enabling the efficient synthesis of high molecular weight and highly branched polyethylene. However, with increasing polymerization temperature and time, the polymerization activity of this type of catalyst needs to be improved, limiting its application in industrial polymerization processes requiring high temperatures. Summary of the Invention

[0004] The purpose of this invention is to provide the synthesis and application of an asymmetric α-diimine nickel catalyst. This invention designs and synthesizes a pyridine-containing asymmetric, sterically hindered α-diimine nickel catalyst. By introducing Lewis acid salts, the steric hindrance and electronic effects of the catalyst are dually regulated. In the olefin polymerization reaction catalyzed by nickel diimine catalysts, Lewis acids play a very subtle "regulator" role, mainly influencing the catalyst's performance and the final polymer structure by altering the electronic properties and spatial environment of the catalyst's active center. Compared with known α-diimine nickel catalysts, this invention has the advantages of high polymerization activity, strong thermal stability, and improved monomer insertion rate.

[0005] The objective of this invention can be achieved through the following technical solutions: An α-diimine nickel catalyst has the following general structural formula: Furthermore, the specific preparation process of the α-diimine nickel catalyst is as follows: Step 1: Aniline 1 was prepared using 2-bromo-4-methylaniline and dibenzyl alcohol as raw materials and anhydrous zinc chloride concentrated hydrochloric acid solution as catalyst.

[0006] Step 2: In the presence of a palladium catalyst and a base, aniline 1 was coupled to pyridine-4-boronic acid via a C-C bond, ultimately generating aniline 2, which contains a benzene ring and a pyridine ring structure.

[0007] Step 3: Ligand L1 is obtained by condensation reaction of the carbonyl group of diacetone with the amino group of aniline 2 under acidic conditions.

[0008] Step 4: Using PTSA catalysis, the amino group of aniline undergoes a condensation reaction with the carbonyl group of ligand L1, removing water and forming an imine bond to obtain ligands L2 and L3 respectively.

[0009] Step 5: Replace the weak ligand DME in the precursor Ni(DME)Br2 with ligands L2 and L3, and then react with Ni. 2+ Stable coordination compounds are formed to obtain the catalyst Ni1-Ni2.

[0010] The present invention also provides an application of α-diimine nickel catalyst as a catalyst for the polymerization reaction of olefins.

[0011] Furthermore, the polymerization reactions of olefins include ethylene homopolymerization and ethylene copolymerization.

[0012] Furthermore, the specific steps of the ethylene homopolymerization reaction are as follows: Under anhydrous and oxygen-free conditions, a co-catalyst and an organic solvent were added to the reaction vessel, and then an α-diimine nickel catalyst was injected under ethylene gas. The polymerization reaction was carried out under ethylene gas at 8 atmospheres. After the reaction was completed, an ethanol solution acidified with hydrochloric acid was added for precipitation.

[0013] Furthermore, the co-catalyst is diethylaluminum chloride; the organic solvent is toluene.

[0014] Furthermore, the specific steps of the ethylene copolymerization reaction are as follows: A co-catalyst, comonomer, and organic solvent were added to the reactor. Then, an α-diimine nickel catalyst was injected under ethylene gas. The polymerization reaction was carried out under ethylene gas at 8 atmospheres. After the reaction was completed, an ethanol solution acidified with hydrochloric acid was added to precipitate the product.

[0015] Furthermore, the cocatalyst is diethylaluminum chloride; the organic solvent is toluene; and the comonomer includes methyl 10-undecenoate, 10-undecenoic acid, 10-undecenol, and 6-chloro-1-hexene. Attached Figure Description

[0016] Figure 1 Catalytic mechanism of asymmetric α-diimine nickel catalyst.

[0017] Figure 2 1H NMR spectrum of aniline 1 (400MHz, CDCl3).

[0018] Figure 3 1H NMR spectrum of aniline 2 (400MHz, CDCl3).

[0019] Figure 4 .Aniline 2 carbon NMR spectrum (400MHz, CDCl3).

[0020] Figure 5 .H NMR spectrum of ligand L1 (400MHz, CDCl3).

[0021] Figure 6 .C NMR spectrum of ligand L1 (400MHz, CDCl3).

[0022] Figure 7 .H NMR spectrum of ligand L2 (400MHz, CDCl3).

[0023] Figure 8 .C NMR spectrum of ligand L2 (400MHz, CDCl3).

[0024] Figure 9 .H NMR spectrum of ligand L3 (400MHz, CDCl3).

[0025] Figure 10 .C NMR spectrum of ligand L3 (400MHz, CDCl3).

[0026] Figure 11 Table 1, GPC data for entry 1.

[0027] Figure 12 Table 1, GPC data for item 2.

[0028] Figure 13 Table 1, GPC data for item 3.

[0029] Figure 14 Table 1, GPC data for item 4.

[0030] Figure 15 Table 1, GPC data for item 5.

[0031] Figure 16 Table 1, GPC data for item 6.

[0032] Figure 17 Table 1, GPC data for item 7.

[0033] Figure 18 Table 1, GPC data for item 8.

[0034] Figure 19 Table 1, GPC data for item 9.

[0035] Figure 20 Table 1, GPC data for item 11.

[0036] Figure 21 Table 1, GPC data for item 12.

[0037] Figure 22 Table 2, GPC data for item 1.

[0038] Figure 23 Table 2, GPC data for item 2.

[0039] Figure 24 Table 2, GPC data for item 3.

[0040] Figure 25 Table 2, GPC data for item 4.

[0041] Figure 26 Table 2, GPC data for item 5.

[0042] Figure 27 Table 2, GPC data for item 6. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1: A mixture of 2-bromo-4-methylaniline (9.3 g, 50 mmol) and benzyl alcohol (9.21 g, 50 mmol) was added to a 250 mL pressure-resistant flask and heated to 120 °C. A solution of anhydrous zinc chloride (3.4 g, 25 mmol) in concentrated hydrochloric acid (37%, 2.24 mL) was added to the mixture, and the temperature was then raised to 160 °C. The mixture was reacted at 160 °C for 30 min, cooled to room temperature, and dissolved in 200 mL of dichloromethane. The product was washed with water (3 × 100 mL), and the solvent was evaporated to obtain the crude product. Then, it was purified by column chromatography (dichloromethane / petroleum ether = 2:3) to give aniline. ¹H NMR (400 MHz, Chloroform-d) δ 7.35–7.21 (m, 6H), 7.19 (s, 1H), 7.11 (d, J = 7.0 Hz, 4H), 6.40 (s, 1H), 5.46 (s, 1H), 3.83 (s, 2H), 2.12 (s, 3H). Example 2: A solution of 2-bromo-4-methylaniline (17.6 g, 50 mmol) in DMF (100 mL) was degassed with nitrogen for 15 min, followed by the addition of Na₂CO₃ solution (30 mL, 2 M) under continuous nitrogen flow. After 10 min, pyridine-4-boronic acid (7.38 g, 60 mmol) and PdCl₂(PPh₃)₂ (0.7 g, 1.0 mmol) were added to the reaction mixture under nitrogen atmosphere. The reaction mixture was heated to 100 °C and stirred for 5 h. After the reaction was complete, the solution was diluted with H₂O (50 mL) and then extracted three times with EtOAc (80 mL). The composite organic layer was dried over anhydrous MgSO₄, and the solvent was removed by rotary evaporation under reduced pressure to obtain the crude product. The crude product was obtained by silica gel column chromatography using petroleum ether / ethyl acetate (2:1) as eluent to give aniline 2 (1.56 g, 85%). 1HNMR(400MHz,Chloroform-d)δ8.59(d,J=6.1Hz,2H),7.33(d,J=6.1Hz,2H),7.28(t,J=7.3Hz,4H),7.20 (d,J=6.8Hz,2H),7.12(d,J=7.0Hz,4H),6.83(s,1H),6.51(s,1H),5.48(s,1H),3.46(s,1H),2.14(s,3H). Example 3: Formic acid (0.5 mL) was added to a methanol (50 mL) solution of dimethyl ethyl ketone (1.72 g, 20 mmol) and aniline 2 (3.5 g, 10 mmol). The mixture was refluxed at 60 °C for 12 h. After cooling, the mixture was filtered, washed with hot methanol (3 × 20 mL), and dried under vacuum to give ligand L1 (0.83 g, 79.6% yield). ¹H NMR (400 MHz, Chloroform-d) δ 8.53 (d, J = 5.4 Hz, 2H), 7.32 (t, J = 7.4 Hz, 2H), 7.28–7.12 (m, 8H), 7.06 (s, 1H), 6.99 (d, J = 7.4 Hz, 2H), 6.85 (s, 1H), 5.48 (s, 1H), 2.45 (s, 3H), 2.31 (s, 3H), 0.75 (s, 3H). Examples 4-5: Weigh L1 and aniline in a molar ratio of 1:1.1 and add them to toluene. Then add a catalytic equivalent of PTSA and reflux the mixture at 120°C for 48 hours with stirring. After the reaction is complete, allow the solution to cool to room temperature, concentrate the solution, recrystallize it, wash the crystals with a small amount of n-hexane, and then dry them under vacuum to remove the solvent, yielding ligands (L2, L3).

[0045] L2:1HNMR(600MHz,Chloroform-d)δ8.51(dd,2H),7.35–7.28(m,4H),7.27–7.20(m,3H),7.20–7.13(m,3H),7.11(s,1H),7.06(d,J =6.9Hz,2H),7.04–6.98(m,2H),6.92–6.84(m,2H),5.59(s,1H),2.33(s,3H),1.96(s,3H),1.91(s,3H),1.74(s,3H),0.96(s,3H); L3:1HNMR(400MHz,Chloroform-d)δ8.51–8.48(m,2H),7.33–7.25(m,4H),7 .25–7.18(m,6H),7.18–7.11(m,3H),7.11–7.00(m,6H),6.83(s,1H),5.58( s,1H),2.44(m,J=6.9Hz,1H),2.30(s,3H),2.19(m,J=6.9Hz,1H),1.97(s,3 H),1.19(d,J=6.9Hz,3H),1.08(dd,J=11.9,6.9Hz,6H),0.95–0.88(m,6H). Examples 6-7: Under nitrogen protection, ligand L2 and Ni(DME)NiBr2 were added to dichloromethane and stirred at room temperature for 12 h. After the reaction was completed, the filtrate was obtained by filtration through a sintered glass core. The dichloromethane was then dried under vacuum and recrystallized with n-hexane. After washing and drying, catalyst Ni1 was obtained. Ni2 was obtained from L3 using the same method.

[0046] Example 8: This example also provides an application of α-diimine nickel catalyst in the catalytic polymerization of olefins to prepare polyethylene. The specific steps are as follows: Under anhydrous and oxygen-free conditions, 0.125 mmol of diethylaluminum chloride, 18 mL of toluene, and a magnetic stir bar were added to a 350 mL thick-walled glass pressure vessel in a glove box. The pressure vessel was connected to a high-pressure line, and the solution was degassed. The vessel temperature was controlled at 20 °C using a water bath and allowed to equilibrate for 15 min. 0.5 μmol Ni1 catalyst in 2 mL of dichloromethane was injected into the polymerization system using a syringe. The reaction vessel was pressurized under rapid stirring and maintained at a constant ethylene pressure of 8.0 atm. After polymerization for 10 min, an ethanol solution acidified with hydrochloric acid was added to the vessel for precipitation. After filtration, the solution was vacuum dried at 50 °C for 24 h. The yield was 0.83 g, and the catalyst activity was 9.96 × 10⁻⁶. 6 g·mol -1 ·h -1， The number-average molecular weight is 394.9 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 1.69 and the branching degree is 58.1.

[0047] Examples 9-10: The difference between these examples and Example 8 is that the temperature was heated to 50°C using an oil bath, while all other experimental conditions remained the same. The mass of the polymerization product was 0.57 g, and the catalyst activity was 6.84 × 10⁻⁶. 6 g·mol -1 ·h -1， The number-average molecular weight was 617,000, the polydispersity index was 2.42, and the degree of branching was 99.1. With the temperature increased to 80℃ and other experimental conditions unchanged, the polymerization product mass was 0.5 g, and the catalyst activity was 6.0 × 10⁻⁶. 6 g·mol -1 ·h -1， The number-average molecular weight is 77.5 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 2.4 and the branching degree is 98.8%.

[0048] Example 11: Under anhydrous and oxygen-free conditions, 0.25 mmol of diethylaluminum chloride, 18 mL of toluene, and a magnetic stir bar were added to a 350 mL thick-walled glass pressure vessel in a glove box. The pressure vessel was connected to a high-pressure line, and the solution was degassed. The vessel temperature was controlled at 20 °C using a water bath and allowed to equilibrate for 15 min. 1 μmol of Ni₂ catalyst in 2 mL of dichloromethane was injected into the polymerization system using a syringe. The reaction vessel was pressurized with rapid stirring and maintained at a constant ethylene pressure of 8.0 atm. After polymerization for 10 min, an ethanol solution acidified with hydrochloric acid was added to the vessel for precipitation. After filtration, the solution was vacuum dried at 50 °C for 24 h. The yield was 0.23 g, and the catalyst activity was 1.38 × 10⁻⁶. 6 g·mol -1 ·h-1， The number-average molecular weight is 67 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 1.95, and the branching degree is 81.4. Examples 12-13: The difference between these examples and Example 11 is that the temperature was heated to 50°C using an oil bath, while all other experimental conditions remained unchanged. The mass of the polymerization product was 0.34, and the catalyst activity was 2.04 × 10⁻⁴. 6 g·mol -1 ·h -1， The number-average molecular weight is 51.6 × 10⁻⁶. 4 g·mol -1 The polydispersity index was 2.24 and the branching degree was 87.6. With the temperature increased to 80℃ and other experimental conditions unchanged, the polymerization product mass was 0.47 g, and the catalyst activity was 2.82 × 10⁻⁶. 6 g·mol -1 ·h -1， The number-average molecular weight is 37.8 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 2.21 and the branching degree is 99.5.

[0049] Example 14: Ni1 and Zn(OTf)2 catalysts were added to 20 mL of dichloromethane at a molar ratio of 2:1 and stirred thoroughly for 12 h. Lewis acid-regulated α-diimine nickel-catalyzed ethylene polymerization was conducted under anhydrous and oxygen-free conditions. 0.25 mmol of diethylaluminum chloride, 18 mL of toluene, and a magnetic stir bar were added to a 350 mL thick-walled glass pressure vessel in a glove box. The pressure vessel was connected to a high-pressure line, and the solution was degassed. The vessel temperature was controlled at 20 °C using a water bath and allowed to equilibrate for 15 min. 0.5 μmol (Ni1 + Zn(OTf)2) catalyst from 2 mL of ethylene was injected into the polymerization system using a syringe. Under rapid stirring, the reaction vessel was pressurized and maintained at a constant ethylene pressure of 8.0 atm. After polymerization for 10 min, an ethanol solution acidified with hydrochloric acid was added to the vessel for precipitation. After filtration, the precipitate was vacuum dried at 50 °C for 24 h. The yield was 0.95 g, and the catalyst activity was 11.4 × 10⁻⁶. 6 g·mol -1 ·h -1， The number-average molecular weight is 385.4 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 1.73 and the branching degree is 73.6.

[0050] Examples 15-16: The difference between these examples and Example 14 is that the temperature was heated to 50°C using an oil bath, while all other experimental conditions remained unchanged. The mass of the polymerization product was 0.56 g, and the catalyst activity was 6.72 × 10⁻⁶. 6 g·mol-1 ·h -1， The number-average molecular weight was 395,000, the polydispersity index was 2.53, and the degree of branching was 102.2. With the temperature increased to 80℃ and other experimental conditions unchanged, the polymerization product mass was 0.44 g, and the catalyst activity was 5.28 × 10⁻⁶. 6 g·mol -1 ·h -1， The number-average molecular weight is 62.3 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 2.48 and the branching degree is 84.1.

[0051] Example 17: The catalysts Ni₂ and Zn(OTf)₂ were added to 20 mL of dichloromethane at a molar ratio of 2:1 and stirred thoroughly for 12 h. Lewis acid-regulated α-diimine nickel-catalyzed ethylene polymerization was conducted under anhydrous and oxygen-free conditions. In a glove box, 0.25 mmol of diethylaluminum chloride, 18 mL of toluene, and a magnetic stir bar were added to a 350 mL thick-walled glass pressure vessel. The pressure vessel was connected to a high-pressure line, and the solution was degassed. The vessel temperature was controlled at 20 °C using a water bath and equilibrated for 15 min. 1 μmol of the (Ni₂ + Zn(OTf)₂) catalyst in 2 mL of ethylene was injected into the polymerization system using a syringe. Under rapid stirring, the reaction vessel was pressurized and maintained at a constant ethylene pressure of 8.0 atm. After polymerization for 10 min, an ethanol solution acidified with hydrochloric acid was added to the vessel for precipitation. After filtration, the precipitate was dried under vacuum at 50 °C for 24 h. The yield was 0.07 g, and the catalyst activity was 0.42 × 10⁻⁶. 6 g·mol -1 ·h -1， The number-average molecular weight is 146.5 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 1.37 and the branching degree is 66.7.

[0052] Examples 18-19: The difference between this embodiment and Example 17 is that the temperature was heated to 50°C using an oil bath, while all other experimental conditions remained the same. The mass of the polymerization product was 0.12 g, and the catalyst activity was 0.72 × 10⁻⁶. 6 g·mol -1 ·h -1， The number-average molecular weight is 72.8 × 10⁻⁶. 4 g·mol -1 The polydispersity index was 1.74 and the degree of branching was 83. With the temperature increased to 80℃ and other experimental conditions unchanged, the polymerization product mass was 0.25, and the catalyst activity was 1.5 × 10⁻⁶. 6 g·mol -1 ·h -1，The number-average molecular weight is 214.1 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 1.14 and the branching degree is 141.7.

[0053] The polymerization results of Experiment 8-19 are summarized in Table 1 below.

[0054] Table 1 Summary of Results: b Yield and activity were calculated at least twice on average. Activity units were counted in units of 10. 6 g·mol -1 ·h -1 . c Molecular weight and molecular weight distribution were determined by GPC in trichlorobenzene at 150°C. Molecular weight is expressed in units of 10. 4 g·mol -1 . d Branching degree is given per 1000 carbon atoms. Branching number per 1000 C atoms = (CH3 / 3) / [(CH+CH2+CH3) / 2] 1000, determined by 1H NMR in C2Cl4D2 at 120 °C.

[0055] Example 20: Under anhydrous and oxygen-free conditions, 1.35 mL of undecenoic acid methyl ester, 11.65 mL of toluene, and a magnetic stir bar were added to a 350 mL thick-walled glass pressure vessel in a glove box. The pressure vessel was connected to a high-pressure pipeline, and the solution was degassed. The vessel temperature was controlled at 50 °C using a water bath and allowed to equilibrate for 15 min. 10 μmol of (Ni1+Zn(OTf)2) catalyst in 5 mL of diethylaluminum chloride and 2 mL of dichloromethane were injected into the polymerization system using a syringe. The reaction vessel was pressurized under rapid stirring and maintained at a constant ethylene pressure of 8.0 atm. After polymerization for 10 min, an ethanol solution acidified with hydrochloric acid was added to the vessel for precipitation. After filtration, the product was vacuum dried at 50 °C for 24 h. The polymer product mass was 0.18 g, and the catalyst activity was 1.08 × 10⁻⁶. 5 g·mol -1 ·h -1 The number-average molecular weight is 10.4 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 2.2 and the branching degree is 0.5.

[0056] Example 21: The difference between this example and Example 20 is that the monomer used is undecenoic acid, with an addition amount of 1.21 mL and 11.79 mL of toluene, while the other experimental conditions remain unchanged. The mass of the polymerization product is 1.78 g, and the catalyst activity is 10.68 × 10⁻⁶.5 g·mol -1 ·h -1 The number-average molecular weight is 25.6 × 10⁻⁶. 4 g·mol -1 The dispersion index is 2.4.

[0057] Example 22: This example differs from Example 20 in that the monomer used is undecenol, with an addition amount of 1.2 mL and 11.8 mL of toluene; all other experimental conditions remain unchanged. The polymerization product mass is 1.6 g, and the catalyst activity is 9.6 × 10⁻⁶. 5 g·mol -1 ·h -1 The number-average molecular weight is 28.7 × 10⁻⁶. 4 g·mol -1 The polydispersity index is 2.2 and the branching degree is 0.3.

[0058] Example 23: This example differs from Example 20 in that the monomer used is replaced with 6-bromo-1-hexene, with an addition amount of 0.8 mL and 12.2 mL of toluene; all other experimental conditions remain unchanged. The polymerization product mass is 0.12, and the catalyst activity is 0.72 × 10⁻⁶. 5 g·mol -1 ·h -1 The number-average molecular weight is 27.1 × 10⁻⁶. 4 g·mol -1 The dispersion index is 2.2.

[0059] Comparative Examples 1-4: The catalyst used in Experiments 20-23 was replaced with Ni1, and the other experimental conditions remained unchanged, and copolymerization was carried out with four different monomers.

[0060] Table 2 summarizes all aggregated data from Experimental Examples 20-23 and Comparative Examples 1-4. Table 2 b Yield and activity were measured at least twice on average. The activity unit was 10. 5 g·mol -1 ·h -1 . c Molecular weight and molecular weight distribution were determined by GPC in trichlorobenzene at 150°C. Molecular weight is expressed in units of 10. 4 g·mol -1 . d Branching degree is given per 1000 carbon atoms. Branching number per 1000 C atoms = (CH3 / 3) / [(CH+CH2+CH3) / 2] 1000, determined by 1H NMR in C2Cl4D2 at 120 °C.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A pyridine-containing asymmetric α-diimine nickel catalyst, characterized in that, Its general structural formula is as follows: 。 2. The pyridine-containing asymmetric α-diimine nickel catalyst according to claim 1, characterized in that, The specific preparation process of the pyridine-containing asymmetric α-diimine nickel catalyst is as follows: Step 1: Using 2-bromo-4-methylaniline and dibenzyl alcohol as raw materials and anhydrous zinc chloride in concentrated hydrochloric acid solution as catalyst, aniline 1 was prepared. Step 2: In the presence of a palladium catalyst and a base, aniline 1 was coupled to pyridine-4-boronic acid via a C-C bond, ultimately generating aniline 2 containing a benzene ring and a pyridine ring structure; Step 3: Ligand L1 is obtained by condensation reaction of the carbonyl group of diacetone with the amino group of aniline 2 under acidic conditions; Step 4: Using PTSA catalysis, the amino group of aniline undergoes a condensation reaction with the carbonyl group of ligand L1, removing water and forming an imine bond to obtain ligands L2 and L3 respectively; Step 5: Replace the weak ligand DME in the precursor Ni(DME)Br2 with ligands L2 and L3, and then react with Ni. 2+ Stable coordination compounds are formed to obtain the catalyst Ni1-Ni2.

3. The application of the pyridine-containing asymmetric α-diimine nickel catalyst according to claim 1 as a catalyst for catalyzing the polymerization reaction of olefins.

4. The application of the pyridine-containing asymmetric α-diimine nickel catalyst according to claim 1 as a catalyst for the polymerization of olefins, characterized in that, The polymerization reactions of the olefins include ethylene homopolymerization and ethylene copolymerization.

5. The application of the pyridine-containing asymmetric α-diimine nickel catalyst according to claim 4 as a catalyst for the polymerization of olefins, characterized in that, The specific steps of the ethylene homopolymerization reaction are as follows: Under anhydrous and oxygen-free conditions, a co-catalyst and an organic solvent were added to the reaction vessel, and then an α-diimine nickel catalyst was injected under ethylene gas. The polymerization reaction was carried out under ethylene gas at 8 atmospheres. After the reaction was completed, an ethanol solution acidified with hydrochloric acid was added for precipitation.

6. The application of the pyridine-containing asymmetric α-diimine nickel catalyst according to claim 5 as a catalyst for catalyzing the polymerization of olefins, characterized in that, The co-catalyst is diethylaluminum chloride; the organic solvent is toluene.

7. The application of the pyridine-containing asymmetric α-diimine nickel catalyst according to claim 4 as a catalyst for the polymerization of olefins, characterized in that, The specific steps of the ethylene copolymerization reaction are as follows: A co-catalyst, comonomer, and organic solvent were added to the reactor. Then, an α-diimine nickel catalyst was injected under ethylene gas. The polymerization reaction was carried out under ethylene gas at 8 atmospheres. After the reaction was completed, an ethanol solution acidified with hydrochloric acid was added to precipitate the product.

8. The application of the pyridine-containing asymmetric α-diimine nickel catalyst according to claim 7 as a catalyst for the polymerization of olefins, characterized in that, The cocatalyst is diethylaluminum chloride; the organic solvent is toluene; and the comonomers include methyl 10-undecenoate, 10-undecenoic acid, 10-undecenol, and 6-chloro-1-hexene.

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