Flexible alkyl chain high steric hindrance Brookhart nickel catalyst, preparation method and application in catalyzing ethylene homopolymerization

Abstract

The present invention relates to the field of catalysis and high molecular weight polyolefin materials, and specifically discloses a flexible alkyl chain high steric hindrance Brookhart nickel-based catalyst, a preparation method and an application in catalyzing ethylene homopolymerization. The introduction of a flexible alkyl chain into a high steric hindrance Brookhart nickel-based catalyst greatly improves the compatibility of the catalyst with alkanes. In addition, the Brookhart nickel-based catalyst substituted with ortho-diaryl groups enhances steric hindrance, better protects the electron density of the metal nickel center, and further improves the polymerization ability of the catalyst. Therefore, this type of catalyst system can efficiently realize ethylene homogeneous polymerization, improve the thermal stability and catalytic activity of the catalyst, obtain a polyethylene with a high molecular weight and a high degree of branching, and the polymer is an elastomer, and such a polymer has a high tensile strength.

Description

Technical Field

[0001] The invention belongs to the field of catalysis and high molecular polyolefin materials, and in particular relates to a flexible alkyl chain high steric hindrance Brookhart nickel catalyst, a preparation method and an application in catalyzing ethylene homopolymerization reaction. Background Art

[0002] Polyolefin materials have the advantages of unique chemical stability, corrosion resistance, excellent mechanical properties and low production cost. At present, they have become the polymer materials with the largest output and the most extensive application, and are gradually changing people's daily lives. In particular, polyethylene accounts for 70% of the world's polyolefin consumption, 44% of the total thermoplastic general-purpose plastic consumption, and consumes 52% of the world's ethylene production. In recent years, the performance of polyethylene materials has been improved and its product categories have been expanded by designing and regulating the topological structure of olefin polymerization catalysts. Polyethylene can be processed by blow molding, extrusion, injection molding and other methods, and is widely used in the manufacture of films, hollow products, fibers and daily sundries.

[0003] In the 1990s, Brookhart et al. first reported that nickel (II) and palladium (Pd)-diimine catalysts can be used to produce high molecular weight polyethylene (Johnson J, Killian C, Brookhart M. New Pd (II) and Ni (II) based catalysts for polymerization of ethylene and α-olefins [J]. J. Am. Chem. Soc. 1995, 117 (23): 6414-6415). The discovery of α-diimine nickel and palladium catalysts has attracted extensive research. Its synthesis method is simple and convenient. By simply adjusting the groups connected to the nitrogen atom and carbon atom of the imine, the steric hindrance and electronic effect of the ligand can be adjusted, thereby changing the catalytic performance of the complex. Studies have shown that the electronic effect of the ortho and para substituents of aniline has a great influence on the performance of the catalyst. Brookhart et al. (Killian CM, Johnson LK, Brookhart M. Preparation of Linear α-Olefins Using Cationic Nickel (II) α-Diimine Catalysts [J]. Organometallics, 1997, 16 (10): 2005-2007.) reported that when the ortho position is bilaterally substituted, high molecular weight polyethylene can be catalyzed, and increasing the ortho steric hindrance can improve the catalytic activity of the catalyst and the molecular weight of the polymer product. However, the thermal stability of the catalyst is poor, and the nickel catalyst decomposes rapidly at temperatures above 60°C. At the same time, researchers have modified the α-diimine ligand skeleton and used it as a ligand to synthesize catalysts. Brookhart et al. (Gates DP, Svejda SA, E, et al. Synthesis of Branched Polyethylene Using (α-Diimine) nickel (II) Catalysts: Influence of Temperature, Ethylene Pressure, and Ligand Structure on Polymer Properties [J]. Macromolecules. 2000, 33, 2320-2334.) synthesized a series of complexes with modified skeletons. The molecular weight and branching degree of polyethylene obtained by using the complexes were improved, and the complexes were still active at 85°C. However, the general Brookhart nickel and palladium catalysts have poor thermal stability and are rapidly deactivated at high temperatures, which limits their application in industry. Therefore, improving the thermal stability of catalysts is a very meaningful research. Summary of the invention

[0004] Therefore, the present invention provides a Brookhart nickel catalyst containing a flexible alkyl chain with large steric hindrance. The catalyst still has high activity at high temperature, has a large molecular weight, and the polymer is an elastomer and has high tensile strength.

[0005] The present invention provides a Brookhart nickel catalyst containing a flexible alkyl chain with large steric hindrance, which catalyzes ethylene homopolymerization reaction, and the structure is shown in (I):

[0006]

[0007] Wherein, R1 is independently methyl, ethyl, n-butyl, tert-butyl, hexyl, 2-ethyl-hexyl; R2 is independently isopropyl, tert-butyl; R3 is independently methoxy, tert-butyl, n-butyl. X is a halogen, such as chlorine (Cl) or bromine (Br).

[0008] The present invention also provides a method for preparing the above catalyst, comprising the following steps:

[0009] Under nitrogen atmosphere, the compound of formula (II) and (DME) NiX2 are reacted in a solvent at a ratio of 1:1 for 6 to 12 hours, filtered, washed, and dried to synthesize a complex of formula (I). The structural formula of the compound of formula (II) is as follows:

[0010]

[0011] R1, R2, and R3 are as defined above.

[0012] The catalyst preparation reaction is as follows:

[0013]

[0014] wherein R1, R2, and R3 are as defined above, and X is a halogen such as chlorine (Cl) or bromine (Br), and DME represents 1,2-dimethoxyethane.

[0015] The nickel precursor compound is (DME)NiBr2 or (DME)NiCl2.

[0016] Furthermore, the preparation method of the compound of formula (II) comprises the following steps:

[0017] (1) Under a nitrogen atmosphere, 4-bromophenol, triphenylphosphine, the corresponding alcohol and diisopropyl azodicarboxylate are added to a solvent for reaction, stirred overnight, the solvent is dried, and the compound (A) is obtained by column chromatography separation, and the reaction is as follows:

[0018]

[0019] (2) Under a nitrogen atmosphere, compound (A) is dissolved in a solvent and placed at low temperature, n-butyl lithium is added, and then benzaldehyde of a para-substituted group is added, reacted for a period of time, and then stirred at room temperature overnight, the solvent is dried by spin drying, extracted, dried, filtered, dried by spin drying, and separated by column chromatography to obtain compound (B), the reaction is as follows:

[0020]

[0021] (3) Compound (B) and aniline are added at 120° C., and then a concentrated hydrochloric acid solution of zinc chloride is added, and the temperature is raised to 160° C. for reaction, and the mixture is cooled to room temperature, extracted, dried, filtered, and spin-dried. Compound (C) is obtained by column chromatography separation, and the reaction is as follows:

[0022]

[0023] (4) In the presence of an organic acid catalyst, diacetyl and compound (C) are reacted in a solvent for 12 to 24 hours, cooled, dried by spin drying, and separated by column chromatography to obtain a compound of formula (II), as follows:

[0024]

[0025] Among them, R1 is independently methyl, ethyl, n-butyl, tert-butyl, hexyl, 2-ethyl-hexyl; R2 is independently isopropyl, tert-butyl; R3 is independently methoxy, tert-butyl, n-butyl.

[0026] The solvent is tetrahydrofuran, dichloromethane, petroleum ether, ethyl acetate, toluene or other mixtures; the organic acid catalyst is one of formic acid, acetic acid and p-toluenesulfonic acid.

[0027] The present invention provides an elastomeric polymer prepared according to the above method, the method comprising: under anhydrous and oxygen-free conditions, adding a solvent and a co-catalyst into a polymerization bottle, connecting the polymerization bottle to a high-pressure polymerization pipeline, and introducing ethylene, then injecting a catalyst dissolved in the solvent, controlling a certain amount of ethylene pressure (1-8atm), reaction temperature (30-120°C), and reaction time (1-30min), adding an alcohol solution containing hydrochloric acid to quench the reaction after the reaction is completed, filtering, and drying to obtain polyethylene.

[0028] Compared with the prior art, the present invention provides a Brookhart nickel complex containing a flexible alkyl chain with large steric hindrance. This type of complex can efficiently polymerize ethylene in the presence of a co-catalyst Et2AlCl. The obtained polymer has a high molecular weight and a high degree of branching, and the polymer is an elastomer and has a high tensile strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1The nuclear magnetic resonance hydrogen spectrum (Ni1, 50°C) of the polymer prepared according to Application Example 1 of the present invention;

[0030] Figure 2 is the tensile strength (Ni1, 50°C) of the polymer prepared according to Application Example 1 of the present invention. DETAILED DESCRIPTION

[0031] In order to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0032] Reagents and raw materials used in the examples: All metal organic reactions were carried out under nitrogen protection, and all solvents were dried and deoxygenated. Anhydrous methanol and ethanol were analytically pure and used directly. Toluene was dehydrated by molecular sieve, refluxed with sodium metal under nitrogen protection, and evaporated before use.

[0033] Example 1: Compound (3E, 2E)-N 3 ,N 2 Synthesis of bis(2,6-bis((4-(tert-butyl)phenyl)(4-((2-ethylhexyl)oxy)phenyl)methyl)-4-methoxyphenyl)butane-2,3-diimine

[0034]

[0035] (1) Under a nitrogen atmosphere, 4-bromophenol (0.17 g, 1.0 mmol), triphenylphosphine (0.34 g, 1.3 mmol) and 2-ethyl-hexanol (0.16 g, 1.2 mmol) were added to tetrahydrofuran (100 mL), and the mixture was placed at 0°C. Diisopropyl azodicarboxylate (0.24 g, 1.2 mmol) was then added, and the mixture was stirred for 15 min and then warmed to room temperature. The reaction was allowed to proceed overnight, and the tetrahydrofuran was then removed by rotary evaporation. Excess petroleum ether was added to precipitate a solid, which was filtered off. The filtrate was dried and concentrated, and the product was obtained by column chromatography (PE / EA=50 / 1). The product was an oily liquid (yield: 90%). 1 H NMR (400MHz, CDCl3, ppm) δ7.4-7.34 (m, 2H), 6.79 (dd, J = 9.0, 1.2Hz, 2H), 3.81 (d, J=5.8Hz,2H),1.73(dt,J=12.1,5.2Hz,1H),1.55-1.26(m,8H),0.98-0.87(m,6H). 13C NMR (100MHz, CDCl3) δ158.53,132.17,116.33,112.48,77.37,77.06,76.74,70.7 5,39.35,31.64,30.51,29.10,26.96,23.85,23.08,22.71,14.17,14.12,11.12.

[0036] (2) In a nitrogen atmosphere at a temperature of -78°C, step 1 (0.29 g, 1 mmol) and n-butyl lithium (0.48 mL, 1.2 mmol) were added to tetrahydrofuran (100 mL). After reacting for 2 h, p-tert-butylbenzaldehyde (0.16 g, 1 mmol) was added and the reaction was continued for 1 h. The temperature was then raised to room temperature and the reaction was allowed to proceed overnight. The tetrahydrofuran was then removed by rotary evaporation, extracted with CH2Cl2 three times, dried over anhydrous magnesium sulfate, filtered, the filtrate was spin-dried, and the product was separated by column chromatography (PE / EA=50 / 1). The product was an oily liquid (yield: 85%). 1 H NMR (400MHz, CDCl3, ppm) δ7.88-7.78(m,2H),7.77-7.65(m,2H),7.54-7.41(m,2H),7.02-6.88 (m,2H),3.93(dd,J=5.7,1.2Hz,2H),1.82-1.72(m,1H),1.57-1.24(m,18H),1.01-0.83(m,7H). 13 C NMR (100MHz, CDCl3) δ195.30,162.96,155.48,135.58,132.49,130.14,129.83,125.14,113.97,77.4 1,77.09,76.77,70.69,53.45,39.32,35.05,31.20,30.50,29.09,23.84,23.06,22.73,14.12,11.14.

[0037] (3) At 120°C, step 2 (0.92 g, 2.5 mmol) and p-methoxyaniline (0.12 g, 1 mmol) were added to a pressure bottle, and zinc chloride solution (zinc chloride was dissolved with a small amount of concentrated hydrochloric acid) was quickly added, and then the temperature was raised to 160°C for 1 h, cooled to room temperature, extracted three times with CH2Cl2, dried over anhydrous magnesium sulfate, filtered, the filtrate was spin-dried, and the product was separated by column chromatography (PE / EA=25 / 1) to obtain the product as a solid (yield: 60%). 1H NMR (400MHz, CDCl3, ppm) δ7.28(d,J=1.8Hz,2H),7.27(d,J=2.0Hz,2H),7.03-6.97(m,8H),6.83-6.78(m,4H),6.21(s,2 H),5.39(s,2H),3.82-3.78(m,4H),3.45(s,3H),1.70(dt,J=12.2,5.8Hz,2H),1.36-1.25(m,31H),1.00-0.84(m,15H). 13 C NMR (100MHz, CDCl3) δ158.04,151.70,149.20,139.83,135.94,134.43,131.3 7,131.34,130.95,130.33,129.02,128.86,127.75,126.14,125.30,114.42,1 14.40,114.06,77.36,77.04,76.73,70.40,70.37,65.60,55.18,51.22,39.44,34.40,31.40,30.55,29.12,23.87,23.08,19.21,14.13,13.77,11.15,0.03.

[0038] (4) Add diacetyl (0.034 g, 0.4 mmol), p-toluenesulfonic acid (20 mg) and aniline from step 3 (0.824 g, 1 mmol) to a reaction bottle containing 100 ml of toluene, condense and reflux, react for 18 h, cool to room temperature, remove toluene by rotary evaporation, and separate by column chromatography (PE / EA=50 / 1) to obtain the product as a solid (yield: 70%). 1 H NMR(400MHz,ppm)δ7.24-7.10(m,8H),7.03-6.84(m,16H),6.77-6.62(m,8H),6.50-6.39(m,4H),5.18-4.98(m,4H) ,3.86-3.62(m,8H),3.56(s,6H),1.65(dq,J=16.5,6.1Hz,4H),1.35-1.20(m,60H),0.89(dt,J=13.4,6.5Hz,25H). 13C NMR (100MHz, CDCl3) δ166.51,158.36,155.03,148.60,138.26,137.36,136.91,132.78,128.11,127.42,121.86,114.1 5,112.63,77.63,57.21,52.34,42.21,34.64,31.74,31.12,29.37,24.59,24.18,16.25,14.64,10.86.Anal.Calc.for C 118 H 156 N2O6:C,83.44;H,9.26;N,1.65.Found:C,83.52;H,9.19;N,1.58.

[0039] Example 2: Compound (3E, 2E)-N 3 ,N 2 Synthesis of bis(2,6-bis((4-(tert-butyl)phenyl)(4-(hexyloxy)phenyl)methyl)-4-methoxyphenyl)butane-2,3-diimine

[0040]

[0041] Similar to Example 1, (1) under a nitrogen atmosphere, 4-bromophenol (0.17 g, 1.0 mmol), triphenylphosphine (0.34 g, 1.3 mmol) and 1-hexanol (0.12 g, 1.2 mmol) were added to tetrahydrofuran (100 mL), and the mixture was placed at 0°C. Diisopropyl azodicarboxylate (0.24 g, 1.2 mmol) was then added, and the mixture was stirred for 15 min and then warmed to room temperature. The reaction was allowed to proceed overnight, and the tetrahydrofuran was then removed by rotary evaporation. Excess petroleum ether was added to precipitate a solid, which was filtered off. The filtrate was dried and concentrated, and the product was obtained by column chromatography (PE / EA=50 / 1). The product was an oily liquid (yield: 85%). 1 HNMR (400MHz, CDCl3, ppm) δ7.44-7.32(m,2H),6.84-6.68(m,2H),3.91(t,J=6.6Hz,2H),1.88-1.65(m,2H),1.52-1.27(m,6H),1.02-0.80(m,3H). 13 C NMR (100MHz, CDCl3) δ158.27,132.20,116.30,112.55,77.38,77.06,76.74,68.26,31.60,29.17,25.71,22.63,14.07.

[0042] (2) In a nitrogen atmosphere, at a temperature of -78°C, step 1 (0.26 g, 1 mmol) and n-butyl lithium (0.48 mL, 1.2 mmol) were added to tetrahydrofuran (100 mL). After reacting for 2 h, p-tert-butylbenzaldehyde (0.16 g, 1 mmol) was added and the reaction was continued for 1 h. The temperature was then raised to room temperature and the reaction was allowed to proceed overnight. The tetrahydrofuran was then removed by rotary evaporation, extracted with CH2Cl2 three times, dried over anhydrous magnesium sulfate, filtered, the filtrate was spin-dried, and the product was separated by column chromatography (PE / EA=50 / 1). The product was an oily liquid (yield: 82%). 1 H NMR (400MHz, CDCl3, ppm) δ7.36-7.31(m,2H),7.30-7.22(m,4H),6.90-6.76(m,2H),5.7 4(s,1H),4.00-3.84(m,2H),1.84-1.69(m,2H),1.51-1.18(m,15H),0.96-0.81(m,3H). 13 C NMR (100MHz, CDCl3) δ158.57,150.30,141.22,136.09,136.07,127.83,126.95,126.21,125.52,12 5.37,114.41,77.42,77.10,76.79,75.67,68.04,34.53,31.64,31.41,29.29,25.78,22.67,14.11.

[0043] (3) At 120°C, step 2 (0.85 g, 2.5 mmol) and p-methoxyaniline (0.12 g, 1 mmol) were added to a pressure bottle, and zinc chloride solution (zinc chloride was dissolved with a small amount of concentrated hydrochloric acid) was quickly added, and then the temperature was raised to 160°C for 1 h, cooled to room temperature, extracted three times with CH2Cl2, dried over anhydrous magnesium sulfate, filtered, the filtrate was spin-dried, and the product was separated by column chromatography (PE / EA=25 / 1) to obtain the product as a solid (yield of 55%). 1 H NMR (400MHz, CDCl3, ppm) δ7.27(d,J=2.0Hz,2H),7.25(s,2H),6.99(d,J=8.0Hz,8H),6.84-6.75(m,4H),6.19(d,J=1.1Hz, 2H),5.38(s,2H),3.99-3.83(m,4H),3.44(d,J=0.9Hz,3H),1.82-1.68(m,4H),1.49-1.12(m,32H),0.90(d,J=2.3Hz,4H). 13C NMR (100MHz, CDCl3) δ157.86,151.79,149.24,139.88,139.86,136.02,134.63,134.60, 131.42,131.40,130.96,130.43,129.09,128.90,125.34,125.33,124.85,114.46,114.4 4,114.15,113.97,111.22,77.44,77.13,76.81,67.96,65.60,55.18,51.29,35.51,34.44,31.68,31.46,30.66,29.38,26.99,26.51,25.84,25.68,22.68,19.27,14.12,13.81.

[0044] (4) Add diacetyl (0.034 g, 0.4 mmol), p-toluenesulfonic acid (20 mg) and aniline from step 3 (0.768 g, 1 mmol) to a reaction bottle containing 100 ml of toluene, condense and reflux, react for 18 h, cool to room temperature, remove toluene by rotary evaporation, and separate by column chromatography (PE / EA=50 / 1) to obtain the product as a solid (yield: 60%). 1 H NMR(400MHz,ppm)δ7.25-7.15(m,8H),7.02-6.84(m,16H),6.77-6.64(m,8H),6.46(d,J=5.2Hz,4H),5.19-4.99(m,4 H),3.98-3.69(m,8H),3.56(s,6H),1.73(ddt,J=17.7,11.4,6.2Hz,8H),1.36-1.19(m,60H),0.90(q,J=6.8Hz,13H). 13 C NMR (100MHz, CDCl3) δ157.56,157.39,155.00,148.60,130.49,130.24,129.22,128.89,125.10,124.89,114.19,114.05,113.96,113.60,77 .35,77.04,76.72,67.88,55.17,50.44,34.32,31.66,31.65,31.39,29.37,29.32,25.81,25.75,22.64,22.62,16.93,14.07.Anal.Calc.for C 110 H 140N2O6:C,83.29;H,8.90;N,1.77.Found:C,83.37;H,8.83;N,1.70.

[0045] Example 3: Compound (3E,2E)-N 3 ,N 2 Synthesis of bis(2,6-bis((4-(tert-butyl)phenyl)(4-ethoxyphenyl)methyl)-4-methoxyphenyl)butane-2,3-diimine

[0046]

[0047] Similar to Example 1, (1) under a nitrogen atmosphere, 4-bromophenol (0.17 g, 1.0 mmol), triphenylphosphine (0.34 g, 1.3 mmol) and ethanol (0.06 g, 1.2 mmol) were added to tetrahydrofuran (100 mL), and the mixture was placed at 0°C. Diisopropyl azodicarboxylate (0.24 g, 1.2 mmol) was then added, and the mixture was stirred for 15 min and then warmed to room temperature. The reaction was allowed to proceed overnight, and the tetrahydrofuran was then removed by rotary evaporation. Excess petroleum ether was added to precipitate a solid, which was filtered off. The filtrate was dried and concentrated, and the product was obtained by column chromatography (PE / EA=50 / 1). The product was an oily liquid (yield: 83%). 1 H NMR (400MHz, CDCl3, ppm) δ7.43-7.30 (m, 2H), 6.77 (dd, J = 8.5, 1.3Hz, 2H), 4.06-3.92 (m, 2H), 1.48-1.36 (m, 3H). 13 C NMR (100 MHz, CDCl 3 )δ158.14,137.35,137.25,133.91,133.72,132.26,128.81,128.63,128.56,116.32,112.65,77.56,77.24,76.92,63.68,14.84.

[0048] (2) In a nitrogen atmosphere at a temperature of -78°C, step 1 (0.20 g, 1 mmol) and n-butyl lithium (0.48 mL, 1.2 mmol) were added to tetrahydrofuran (100 mL). After reacting for 2 h, p-tert-butylbenzaldehyde (0.16 g, 1 mmol) was added and the reaction was continued for 1 h. The temperature was then raised to room temperature and the reaction was allowed to proceed overnight. The tetrahydrofuran was then removed by rotary evaporation, extracted with CH2Cl2 three times, dried over anhydrous magnesium sulfate, filtered, the filtrate was spin-dried, and the product was separated by column chromatography (PE / EA=50 / 1). The product was an oily liquid (yield: 82%). 1H NMR (400MHz, CDCl3, ppm) δ7.39-7.30(m,2H),7.29-7.20(m,4H),6.85-6.80(m,2H),5.72(s,1H),3.98(q,J=7.0Hz,2H),1.41-1.24(m,12H). 13 C NMR (100MHz, CDCl3) δ158.40,158.33,150.49,150.18,150.07,141.43,139. 66,138.16,136.45,135.72,134.48,128.90,128.74,128.65,128.01,127.7 6,127.10,127.02,126.95,126.40,125.45,125.35,114.45,81.96,79.36,77.64,77.32,77.00,75.56,70.27,64.81,63.51,34.63,34.59,31.55,14.98.

[0049] (3) At 120°C, step 2 (0.71 g, 2.5 mmol) and p-methoxyaniline (0.12 g, 1 mmol) were added to a pressure bottle, and zinc chloride solution (zinc chloride was dissolved with a small amount of concentrated hydrochloric acid) was quickly added, and then the temperature was raised to 160°C for reaction for 1 h, cooled to room temperature, extracted three times with CH2Cl2, dried over anhydrous magnesium sulfate, filtered, the filtrate was spin-dried, and the product was separated by column chromatography (PE / EA=25 / 1) to obtain the product as a solid (yield 55%). 1 H NMR (400MHz, CDCl3, ppm) δ7.30-7.23(m,5H),7.03-6.97(m,7H),6.82-6.77(m,4H),6.19(d,J=1.8Hz, 2H),5.38(s,2H),4.03-3.94(m,4H),3.44(d,J=1.2Hz,3H),1.44-1.36(m,6H),1.29(d,J=1.1Hz,19H). 13 C NMR (100MHz, CDCl3) δ157.61,151.77,149.24,139.76,135.92,134.69,134.65,131.39,130.40, 129.03,125.29,114.40,114.11,77.35,77.03,76.72,63.35,55.17,51.22,34.40,31.39,14.90.

[0050] (4) In a reaction flask containing 100 ml of toluene, diacetyl (0.034 g, 0.4 mmol), p-toluenesulfonic acid (20 mg) and aniline from step 3 (0.656 g, 1 mmol) were added. The mixture was condensed and refluxed for 18 h. The mixture was cooled to room temperature, and the toluene was removed by rotary evaporation. The product was separated by column chromatography (PE / EA=50 / 1) and was obtained as a solid (yield: 60%). 1 H NMR(400MHz,ppm)δ7.25-7.15(m,8H),7.01-6.85(m,16H),6.72(ddt,J=16.3,8.3,5.0Hz,8H),6.45(d,J= 4.3Hz,4H),5.20-4.97(m,4H),4.03-3.79(m,8H),3.56(s,6H),1.40(d,J=6.8Hz,6H),1.30-1.22(m,42H). 13 C NMR (100MHz, CDCl3) δ167.36,159.19,155.60,148.61,139.75,138.35,135.28,133.81,128.31,126. 54,123.24,114.13,112.66,113.60,66.48,55.71,50.36,34.41,31.32,15.42,14.03.Anal.Calc.for C 94 H 108 N2O6:C,82.90;H,7.99;N,2.06.Found:C,82.98;H,7.92;N,1.99.

[0051] Example 4: Synthesis of Nickel Complex Ni1

[0052]

[0053] Under nitrogen atmosphere, add the compound prepared in Example 1 to dichloromethane, then add (DME)NiBr2, the molar ratio of which is 1:1, react for 12 hours, filter with diatomaceous earth, wash with dichloromethane, dry, and then wash three times with anhydrous ether to obtain orange-red solid Ni1 (yield is 85%). Anal.Calc.for C 118 H 156 Br2N2NiO6:C,73.96;H,8.20;N,1.46.Found:C,74.04;H,8.13;N,1.39.

[0054] Example 5: Synthesis of Nickel Complex Ni2

[0055]

[0056] Similar to Example 4, under nitrogen atmosphere, the compound prepared in Example 2 was added to dichloromethane, and then (DME)NiBr2 was added at a molar ratio of 1:1. After reacting for 12 hours, the mixture was filtered with diatomaceous earth, washed with dichloromethane, dried, and then washed three times with anhydrous ether to obtain orange-red solid Ni2 (yield 88%). 110 H 140 Br2N2NiO6:C,73.20;H,7.82;N,1.55.Found:C,73.28;H,7.75;N,1.48.

[0057] Example 6: Synthesis of Nickel Complex Ni3

[0058]

[0059] Similar to Example 4, under nitrogen atmosphere, the compound prepared in Example 2 was added to dichloromethane, and then (DME)NiBr2 was added at a molar ratio of 1:1. After reacting for 12 hours, the mixture was filtered with diatomaceous earth, washed with dichloromethane, dried, and then washed three times with anhydrous ether to obtain orange-red solid Ni3 (yield 80%). 94 H 108 Br2N2NiO6:C,71.44;H,6.89;N,1.77.Found:C,71.52;H,6.82;N,1.70.

[0060] Application Example 1

[0061] Application of catalytic ethylene polymerization

[0062] First, place a 350mL thick-walled pressure-resistant bottle with a magnet in an oven at 100°C for 4 to 8 hours, and bring it into a glove box by replacing nitrogen. Then, add 20mL of n-heptane to the pressure-resistant bottle, take it out, connect it to a high-pressure gas pipeline with ethylene gas, and raise the temperature to the required temperature. At the same time, turn on the vacuum pump to evacuate the polymerization gas pipeline, and turn off the vacuum pump after 3 minutes. Ethylene is introduced, and nickel complex (2.6μmol) and diethylaluminum chloride (1300μmol) dissolved in 2mL of dichloromethane are injected into the polymerization pressure-resistant bottle with a syringe under an ethylene atmosphere, and the pressure reducing valve is slowly adjusted to the required polymerization pressure and maintained, and the time is recorded. Finally, the polymerization reaction is terminated, and a large amount of 5% (volume) acidified anhydrous ethanol is added, the polymer is precipitated, filtered, washed with anhydrous ethanol several times, and dried in a vacuum drying oven at 60°C for 24 hours. The following table shows the experimental conditions for ethylene polymerization provided by the present invention; catalyst (Cat.), temperature (T), yield (Yield), catalytic activity (Act.), polymer molecular weight (Mn ), polymer molecular weight distribution (PDI), degree of branching (B) and other polymerization result data.

[0063] Table 1 Ethylene polymerization a

[0064]

[0065] a Polymerization conditions: catalyst 2.6 μmol, dichloromethane = 2 mL, [Al] / [Ni] = 500, n-heptane = 20 mL, ethylene pressure 8 atm, time = 5 min;

[0066] b The unit of activity is 10 6 g mol -1 h -1 ;

[0067] c Polymer molecular weight M n and molecular weight distribution PDI were determined by gel permeation chromatography (GPC) at 150 °C in trichlorobenzene and polystyrene standards;

[0068] d The degree of branching refers to the number of branches per 1000 carbon atoms, which is 1 H NMR nuclear magnetic resonance determination;

[0069] e Melting point m Determined by differential scanning calorimetry (DSC).

[0070] As can be seen from Table 1, the Ni1, Ni2, and Ni3 catalysts prepared by the present invention can all catalyze the preparation of polyethylene with high activity, especially at 120°C, the catalysts still have high activity (conventional catalysts are deactivated at high temperatures). This is mainly due to the larger steric hindrance protecting the nickel active center, which makes it have better heat resistance at high temperatures. At the same time, the molecular weight and branching degree of the prepared polymer are high, and the polymer is an elastomer with high tensile strength.

[0071] The above is a detailed introduction to a compound, a complex catalyst, a catalyst composition and a method for preparing an olefin polymer provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention, but the present invention is not limited to the specific implementation methods described herein. It is understood by those skilled in the art that other changes and modifications may be made without departing from the scope of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. Flexible alkyl chain sterically hindered Brookhart nickel catalyst, characterized by: The structure of the complex is shown in formula (I): （Ⅰ）， Wherein, R1 is hexyl or 2-ethyl-hexyl; R2 is tert-butyl; R3 is methoxy; X is halogen; The nickel-based catalyst is used for catalyzing ethylene polymerization to prepare polyethylene elastomer, and the application includes the following steps: under anhydrous and oxygen-free conditions, adding a solvent and a co-catalyst Et2AlCl into a polymerization bottle, connecting the polymerization bottle to a high-pressure polymerization pipeline, and introducing ethylene, and then injecting a catalyst dissolved in the solvent, controlling the ethylene pressure to 1-8atm, reacting at 30-120°C for 1-30min, adding an alcohol solution containing hydrochloric acid to quench the reaction after the reaction is completed, filtering, and drying to obtain a polyethylene elastomer.

2. A method for preparing the flexible alkyl chain high steric hindrance Brookhart nickel catalyst as claimed in claim 1, characterized in that: The method comprises the following steps: reacting a compound of formula (II) with (DME)NiX2 in a solvent at a molar equivalent ratio of 1:1 under a nitrogen atmosphere for 6 to 12 hours, filtering, washing, and drying to synthesize a catalyst of formula (I). The structural formula of the compound of formula (II) is as follows: （Ⅱ）。 3. The method for preparing the flexible alkyl chain high steric hindrance Brookhart nickel catalyst according to claim 2, characterized in that: (DME)NiX2 is (DME)NiBr2 and (DME)NiCl2.

4. The use of the flexible alkyl chain high steric hindrance Brookhart nickel catalyst according to claim 1, characterized in that: Used to catalyze the polymerization of ethylene to prepare polyethylene elastomers.

5. The use of the flexible alkyl chain high steric hindrance Brookhart nickel catalyst according to claim 4, characterized in that: The steps include: Under anhydrous and oxygen-free conditions, the solvent and the co-catalyst are added into a polymerization bottle, the polymerization bottle is connected to a high-pressure polymerization pipeline, and ethylene is introduced, and then the catalyst dissolved in the solvent is injected, the ethylene pressure is controlled at 1-8 atm, and the reaction is carried out at 30-120°C for 1-30 min. After the reaction is completed, an alcohol solution containing hydrochloric acid is added to quench the reaction, and the reaction is filtered and dried to obtain polyethylene.

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