Preparation of alpha-diimine nickel complex and application of alpha-diimine nickel complex in olefin polymerization
By controlling the steric hindrance of the ligands in the α-diimine nickel complex, the problems of low catalyst activity and poor thermal stability in the prior art were solved, realizing efficient and controllable long-chain α-olefin polymerization, which has good potential for industrial application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHU INST OF TECH
- Filing Date
- 2026-02-05
- Publication Date
- 2026-05-26
AI Technical Summary
Existing α-diimine nickel complexes exhibit low activity and poor thermal stability in catalyzing the polymerization of long-chain α-olefins, making it difficult to achieve efficient and controllable polymer structure regulation.
By precisely controlling the steric hindrance of the ligands, α-diimine nickel complexes were prepared. Using specific solvents and reaction conditions, complexes with excellent thermal stability and high catalytic activity were formed.
It maintains high catalytic activity over a wide temperature range, enabling directional control of polymer branching degree and molecular weight. It is suitable for the efficient polymerization of long-chain α-olefins and has good potential for industrial application.
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Figure CN122080084A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of olefin polymerization technology, specifically to the preparation of an α-diimine nickel complex and its application in olefin polymerization. Background Technology
[0002] Polyolefins, as an important class of polymer materials, are widely used in many fields such as electrical equipment, automotive parts, food packaging, and household appliances due to their excellent physicochemical properties, good processing adaptability, and low cost. Among them, polyethylene and long-chain α-olefin polymers are important members of the polyolefin family. Their properties are closely related to structural characteristics such as molecular weight, molecular weight distribution, degree of branching, and stereoregularity, and these structural characteristics are largely regulated by the performance of polymerization catalysts.
[0003] In the field of olefin coordination polymerization, post-transition metal catalysts have attracted much attention due to their potential in catalytic activity, polymer structure regulation, and functionalization. In particular, α-diimine nickel complexes have become a research hotspot because they can prepare branched polyethylene in ethylene polymerization.
[0004] However, in the existing technology, the research and application of this type of catalyst mainly focus on the homopolymerization of ethylene and its copolymerization with polar monomers. Research on the catalytic polymerization of long-chain α-olefins (such as propylene, 1-octene, 1-decene, etc.) is relatively scarce, and the following technical problems are common: the known α-diimine nickel complexes often have low activity when catalyzing the polymerization of long-chain α-olefins, which is difficult to meet the needs of efficient industrial production; when polymerization is carried out at higher temperatures, the catalyst is prone to deactivation, affecting the stability of the polymerization process and the consistency of polymer performance; the mechanism by which the steric hindrance of the catalyst ligand regulates the molecular weight, branching degree and stereoregularity of the polymer is unclear, making it difficult to accurately design the catalyst structure according to product requirements and achieve controllable customization of polymer performance.
[0005] Therefore, developing a class of α-diimine nickel catalysts that combine high activity, good thermal stability, and excellent polymer structure control capabilities, especially catalyst systems suitable for the efficient polymerization of long-chain α-olefins, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing α-diimine nickel complexes and their application in olefin polymerization, thereby solving the technical problem that "existing α-diimine nickel complexes have insufficient comprehensive performance in catalyzing the polymerization of long-chain α-olefins, making it difficult to achieve efficient and controllable polymerization".
[0007] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides an α-diimine nickel complex, the structure of which is shown in formula (I): (I) In formula (I), R is selected from one of the substituted phenyl, isopropyl, alkyl, fluorine, chlorine, bromine, iodine, nitro, hydroxyl, and silyl groups from C1 to C20; wherein the R parts can also bond to each other to form a ring.
[0008] Secondly, the present invention provides a method for preparing an α-diimine nickel complex, wherein the synthesis process of the complex is as follows: (1) Dissolve acenaphthene in acetonitrile, heat and stir for 15 min to form a reaction mixture, then slowly add glacial acetic acid to the mixture, followed by aniline compounds, wherein the weight ratio of acenaphthene, acetonitrile and glacial acetic acid is 1:(15.2~16):(8~8.2), and continue the reaction for 4~10 h to obtain the ligand; (2) Under an inert gas atmosphere, the ligand is dissolved in a good solvent, Ni(DME)Br2 is added to react, and after concentration, a poor solvent is added to recrystallize to obtain the α-diimine nickel complex.
[0009] Specifically, the structure of the aniline compound in step (1) is as follows: R is selected from one of the following C1~C20 substituted phenyl, isopropyl, alkyl, fluorine, chlorine, bromine, iodine, nitro, hydroxyl, and silyl groups; wherein the R moieties can also bond to each other to form a ring.
[0010] Specifically, the structure of the ligand in step (1) is shown in equation (II) below: (II) In formula (II), R is selected from one of the substituted phenyl, isopropyl, alkyl, fluorine, chlorine, bromine, iodine, nitro, hydroxyl, and silyl groups from C1 to C20; wherein the R parts can also bond to each other to form a ring.
[0011] In this invention, the molar ratio of acenaphthene to aniline compounds in step (1) is 1:(2~2.5).
[0012] In this invention, the molar ratio of ligand to Ni(DME)Br2 in step (1) is 1:(1.1~1.5).
[0013] In this invention, the good solvent in step (2) is one of dichloromethane, toluene, xylene, and trichlorobenzene.
[0014] In this invention, the undesirable solvent in step (2) is one of diethyl ether, petroleum ether, n-hexane, n-pentane, and n-heptane.
[0015] Thirdly, the present invention provides the application of the above-mentioned α-diimine nickel complex in initiating homogeneous polymerization of ethylene and polymerization of long-chain α-olefins.
[0016] In this invention, the long-chain α-olefin is one or a mixture of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 1-decene, 1-dodecene, and 1-octadecene. Compared with the prior art, the beneficial effects achieved by the present invention are: (1) By precisely controlling the steric hindrance of the ligands, the nickel α-diimine complex prepared by this invention exhibits excellent thermal stability and high catalytic activity, maintaining high efficiency over a wide temperature range, with an ethylene polymerization activity reaching 5.06 × 10⁻⁶. 6 g·mol -1 ·h -1 The polymerization activity of 1-octene can reach 3.54 × 10⁻⁶. 5 g·mol -1 ·h -1 .
[0017] (2) The spatial effect of the complex of the present invention can effectively regulate the chain walking and growth during the polymerization process, realize the directional control of the branching degree and molecular weight of polyethylene, and can efficiently catalyze long-chain α-olefins to obtain high molecular weight polymers.
[0018] (3) This invention extends the α-diimine nickel catalyst system to the efficient polymerization of long-chain α-olefins, and the synthesis method is simple, the process compatibility is good, and it has good potential for industrial application. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the polymerization reaction of ethylene or long-chain α-olefins catalyzed by the α-diimine nickel complex in this invention.
[0020] Figure 2 The 1H NMR spectrum of II1 in Example 1 is shown.
[0021] Figure 3 This is the carbon NMR spectrum of II1 in Example 1.
[0022] Figure 4 The 1H NMR spectrum of II2 in Example 2 is shown.
[0023] Figure 5 This is the carbon NMR spectrum of II2 in Example 2.
[0024] Figure 6 The 1H NMR spectrum of II3 in Example 3 is shown.
[0025] Figure 7 This is the carbon NMR spectrum of II3 in Example 3.
[0026] Figure 8 The 1H NMR spectrum of II4 in Example 4 is shown.
[0027] Figure 9 This is the carbon NMR spectrum of II4 in Example 4. Detailed Implementation
[0028] 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.
[0029] According to an embodiment of this application, an α-diimine nickel complex is provided, the complex having the structure of formula (I): (I) Preferably, the complexes of the formula (I) structure include formula (I1), formula (I2), formula (I3), and formula (I4).
[0030] (I1) (I2) (I3) (I4) The -Ph-F structure in I4 is .
[0031] This invention also provides a method for preparing an α-diimine nickel complex, comprising the following steps: (1) Under nitrogen protection, add acenaphthene to a Schlenk flask, then add acetonitrile, heat to 40~100℃, stir for 15min, slowly add glacial acetic acid to the reaction mixture, wherein the weight ratio of acenaphthene, acetonitrile and glacial acetic acid is 1:(15.2~16):(8~8.2), then add aniline compounds, wherein the molar ratio of acenaphthene to aniline compounds is 1:(2~2.5), continue the reaction at this temperature for 4~10h, cool and filter, wash with n-hexane, collect the filter cake to obtain the ligand; (2) Under nitrogen protection, the ligand was dissolved in dichloromethane at a weight ratio of 1: (83~84). Ni(DME)Br2 was added at a molar ratio of 1: (1.1~1.5). The mixture was stirred at 25°C for 1~12 h, filtered, and the filtrate was concentrated to obtain a solid. The solid was washed three times with diethyl ether, filtered, and the filter cake was collected and dried to obtain the α-diimine nickel complex.
[0032] According to an embodiment of this application, a ligand is provided having the structure of formula (II): (II) Preferably, the aniline compounds include: 4-(bis(4-fluorophenyl)methyl)-2,6-dimethylaniline, 4-(bis(4-fluorophenyl)methyl)-2,6-diethylaniline, 4-(bis(4-fluorophenyl)methyl)-2,6-diisopropylaniline, and 2,4,6-tris(bis(4-fluorophenyl))aniline.
[0033] Preferably, the complexes of the formula (II) structure include formula (II1), formula (II2), formula (II3), and formula (II4).
[0034] (II1) (II2) (II3) (II4) According to embodiments of this application, an application of α-diimine nickel complexes in catalyzing olefin polymerization is also provided.
[0035] The following examples illustrate the specific content of the present invention. The data provided include the synthesis of ligands, the synthesis of complexes, and methods for ethylene polymerization or copolymerization. The synthesis of complexes and polymerization processes are carried out under anhydrous and oxygen-free conditions. All sensitive substances are stored in glove boxes, and all solvents are strictly dried and dehydrated. Ethylene gas is purified by passing it through a dehydration and deoxygenation column. Monomers such as long-chain α-olefins are purified by dehydration, deoxygenation, and vacuum distillation. Unless otherwise specified, all raw materials are purchased from the market.
[0036] NMR was performed using a Bruker 400MHz NMR instrument; elemental analysis was conducted by the Physics and Chemistry Center of the University of Science and Technology of China; molecular weight and molecular weight distribution were determined by GPC (polystyrene column, HR2 and HR4, oven temperature 150℃, using Water1515 and Water 2414 pumps; mobile phase was trichlorobenzene, flow rate was 1.0 mL / min, and polydisperse polystyrene was used as the standard).
[0037] I. Preparation of Complex I Example 1; Preparation of I1 (1) Under nitrogen protection, add acenaphthene (0.91 g, 5 mmol) to a Schlenk flask, then add 17.6 mL of acetonitrile, heat to 40 °C, stir for 15 min, slowly add 6.93 mL of glacial acetic acid to the reaction mixture, then add 4-(bis(4-fluorophenyl)methyl)-2,6-dimethylaniline (3.23 g, 10 mmol), continue the reaction at this temperature for 4 h, cool and filter, wash with n-hexane, collect the filter cake to obtain II1 (3.17 g, 80% yield); (2) Under nitrogen protection, I1 (0.32 g, 0.40 mmol) was dissolved in 20 mL of dichloromethane, and Ni(DME)Br2 (0.136 g, 0.44 mmol) was added. The mixture was stirred at 25 °C for 1 h, filtered, and the filtrate was concentrated to obtain a solid. The solid was washed three times with diethyl ether, filtered, and the filter cake was collected and dried to obtain I1 (0.32 g, 78% yield).
[0038] The hydrogen nuclear magnetic spectrum of II1 is: 1H NMR (400MHz, Chloroform-d): δ8.19- 8.12(m,4H,Ar-H),8.05(d,J=8.6Hz,1H,Ar-H),7.86(d,J=7.2Hz,1H,Ar-H),7.42(d,J=7.6Hz,1H, Ar-H),7.09(s,7H,Ar-H),7.06-7.02(m,7H,Ar-H),6.84(d,J=6.4Hz,5H,Ar-H),5.52(s,2H,-CHAr 2) ,2.00(s,12H,-CH3).
[0039] The carbon NMR spectrum of II1 is as follows: 13 C NMR (101MHz, Chloroform-d): δ189.60, 162.80,160.38,147.25,143.04,139.87,132.27,131.05,129.48,128.61,127.87,124.76,122.44,115.33,54.95,18.13.
[0040] Elemental analysis C 54 H 40 Theoretical values of F4N2: C, 81.80; H, 5.08; N, 3.53; Experimental values: C, 81.77; H, 5.04; N, 3.55.
[0041] Example 2; Preparation of I2 (1) Under nitrogen protection, add acenaphthene (0.91 g, 5 mmol) to a Schlenk flask, then add 18 mL of acetonitrile, heat to 60 °C, stir for 15 min, slowly add 7 mL of glacial acetic acid to the reaction mixture, then add 4-(bis(4-fluorophenyl)methyl)-2,6-diethylaniline (3.87 g, 11 mmol), continue the reaction at this temperature for 6 h, cool and filter, wash with n-hexane, collect the filter cake to obtain II2 (3.48 g, 82% yield); (2) Under nitrogen protection, I2 (0.34 g, 0.40 mmol) was dissolved in 20 mL of dichloromethane, and Ni(DME)Br2 (0.132 g, 0.44 mmol) was added. The mixture was stirred at 25 °C for 2 h, filtered, and the filtrate was concentrated to obtain a solid. The solid was washed three times with diethyl ether, filtered, and the filter cake was collected and dried to obtain I2 (0.36 g, 85% yield).
[0042] The 1H NMR spectrum of II2 is as follows: 1H NMR (400MHz, Chloroform-d): δ 7.94 (d, J = 8.2Hz, 2H, Ar-H), 7.35 (d, J = 7.4Hz, 2H, Ar-H), 7.21-7.01 (m, 16H, Ar-H), 6.93-6.79 (m, 4H, Ar-H), 6.74 (d, J = 8.2Hz, 2H, Ar-H), 5.52 (s, 2H, -CHAr2), 2.44 (d, J = 7.2Hz, 8H, Ar-CH2CH3), 1.15 (s, 2H, -CH3), 1.07 (s, 10H, -CH3).
[0043] The carbon NMR spectrum of II2 is as follows: 13 C NMR (101MHz, Chloroform-d): δ162.77, 160.66,147.26,140.18,140.02,131.17,131.05,130.72,129.67,129.02, 128.31,128.09,123.05,115.25,55.18,24.96,14.17.
[0044] Elemental analysis C 58 H 48 Theoretical values for F4N2: C, 82.05; H, 5.70; N, 3.30; Experimental values: C, 82.07; H, 5.73; N, 3.28.
[0045] Example 3; Preparation of I3 (1) Under nitrogen protection, add acenaphthene (0.91 g, 5 mmol) to a Schlenk flask, then add 18 mL of acetonitrile, heat to 80 °C, stir for 15 min, slowly add 7 mL of glacial acetic acid to the reaction mixture, then add 4-(bis(4-fluorophenyl)methyl)-2,6-diisopropylaniline (4.17 g, 11 mmol), continue the reaction at this temperature for 8 h, cool and filter, wash with n-hexane, collect the filter cake to obtain II3 (3.66 g, 81% yield); (2) Under nitrogen protection, I13 (0.36 g, 0.40 mmol) was dissolved in 20 mL of dichloromethane, and Ni(DME)Br2 (0.132 g, 0.44 mmol) was added. The mixture was stirred at 25 °C for 6 h, filtered, and the filtrate was concentrated to obtain a solid. The solid was washed three times with diethyl ether, filtered, and the filter cake was collected and dried to obtain I3 (0.38 g, 85% yield).
[0046] The 1H NMR spectrum of II3 is as follows: 1H NMR (400MHz, Chloroform-d): δ 7.81 (d, J = 8.2Hz, 2H, Ar-H), 7.27 (s, 2H, Ar-H), 7.07-6.97 (m, 10H, Ar-H), 6.84-6.73 (m, 8H, Ar-H), 6.54 (d, J = 7.2Hz, 2H, Ar-H), 5.50 (s, 2H, -CHAr2), 2.99-2.85 (m, 4H, -CH2(CH3)2), 1.03 (d, J = 6.8Hz, 12H, -CH3), 0.77 (d, J = 6.8Hz, 12H, -CH3).
[0047] The carbon NMR spectrum of II3 is as follows: 13 C NMR (101MHz, Chloroform-d): δ162.35, 160.96,146.16,140.59,139.27,135.57,131.28,130.87,130.82,129.36, 128.96,127.78,124.59,123.30,115.21,55.43,28.76,23.35,23.07.
[0048] Elemental analysis C 62 H 56 Theoretical values for F4N2: C, 82.27; H, 6.24; N, 3.09; Experimental values: C, 82.28; H, 6.25; N, 3.08.
[0049] Example 4; Preparation of I4 (1) Under nitrogen protection, acenaphthene (0.91 g, 5 mmol) was added to a Schlenk flask, followed by 18.52 mL of acetonitrile. The mixture was heated to 100 °C and stirred for 15 min. 7.11 mL of glacial acetic acid was slowly added to the reaction mixture, followed by 2,4,6-tris(bis(4-fluorophenyl))aniline (6.04 g, 12.5 mmol). The reaction was continued at this temperature for 10 h. After cooling, the mixture was filtered, washed with n-hexane, and the filter cake was collected to obtain II4 (4.5 g, 81% yield). (2) Under nitrogen protection, I14 (0.62 g, 0.40 mmol) was dissolved in 20 mL of dichloromethane, and Ni(DME)Br2 (0.185 g, 0.60 mmol) was added. The mixture was stirred at 25 °C for 12 h, filtered, and the filtrate was concentrated to obtain a solid. The solid was washed three times with diethyl ether, filtered, and the filter cake was collected and dried to obtain I4 (0.53 g, 75% yield).
[0050] The 1H NMR spectrum of II4 is as follows: 1H NMR (400MHz, Chloroform-d): δ 8.11-8.05 (m, 3H, Ar-H), 7.85-7.76 (m, 3H, Ar-H), 6.93 (d, J=6.8Hz, 15H, Ar-H), 6.87-6.84 (m, 15H, Ar-H), 6.67-6.61 (m, 8H, Ar-H), 6.58 (s, 4H, Ar-H), 6.25-6.16 (m, 8H, Ar-H), 5.87 (d, J=7.2Hz, 2H, Ar-H), 5.43 (s, 4H, -CHAr2), 5.39 (s, 2H, -CHAr2).
[0051] The carbon NMR spectrum of II4 is as follows: 13 C NMR (101MHz, Chloroform-d): δ160.31,139.37,138.09,137.05,132.51,130.93,130.57,130.28,129.44, 129.20,128.19,126.87,123.67,115.23,114.87,54.64,51.17.
[0052] Elemental analysis C 102 H 64 F 12 Theoretical N2 values: C, 79.26; H, 4.17; N, 1.81; Experimental values: C, 79.29; H, 4.68; N, 1.83.
[0053] II. Catalytic olefin polymerization Example 5: I1-catalyzed ethylene polymerization In a glove box under a nitrogen atmosphere, 28 mL of toluene and 1250 μmol of Et₂AlCl were added to an autoclave. The container was then connected to a high-pressure pipeline, and the pipeline was evacuated. The container temperature was set to 60 °C and maintained for 5 min. 2.5 μmol of I₁ and 750 μmol of Et₂AlCl prepared in Example 1 were dissolved in 2 mL of dichloromethane and injected into the autoclave using a syringe. Then, the ethylene valve was opened, ethylene was introduced into the autoclave, and the ethylene pressure was adjusted to 8 atm. The reaction was allowed to proceed for 15 min. The reaction was then stopped, the autoclave was opened, and ethanol was added to precipitate the solid. The mixture was filtered under reduced pressure and dried in a vacuum drying oven to obtain a white solid, L₁.
[0054] Example 6: I2-catalyzed ethylene polymerization yields L2, prepared in the same manner as in Example 5, except that the 2.5 μmol I1 prepared in Example 1 is replaced with the 2.5 μmol I2 prepared in Example 2.
[0055] Example 7: I3 catalyzes the polymerization of ethylene to obtain L3. The preparation process is the same as in Example 5, except that the 2.5 μmol of I1 prepared in Example 1 is replaced with the 2.5 μmol of I3 prepared in Example 3.
[0056] Example 8: I4 catalyzes the polymerization of ethylene to obtain L4. The preparation process is the same as in Example 5, except that the 2.5 μmol I1 prepared in Example 1 is replaced with the 2.5 μmol I4 prepared in Example 4.
[0057] Example 9: I1-catalyzed polymerization of 1-octene to obtain L5 In a glove box under a nitrogen atmosphere, 10 mL of toluene, 5000 μmol of Et₂AlCl, and 2.24 g of 1-octene were added to an autoclave. The container was then connected to a high-pressure pipeline and evacuated. The container temperature was set to 60 °C and maintained for 5 min. 10 μmol of I₁ and 3000 μmol of Et₂AlCl prepared in Example 1 were dissolved in 2 mL of dichloromethane and added to the autoclave. The reaction was allowed to proceed for 30 min. The autoclave was then opened, and ethanol was added to precipitate the solid. The mixture was filtered under reduced pressure to obtain L₅.
[0058] Example 10: I2 catalyzes the polymerization of 1-octene to obtain L6. The preparation process is the same as in Example 9, except that the 10 μmol of I1 prepared in Example 1 is replaced with the 10 μmol of I2 prepared in Example 2.
[0059] Example 11: I3 catalyzes the polymerization of 1-octene to obtain L7. The preparation process is the same as in Example 9, except that the 10 μmol I1 prepared in Example 1 is replaced with the 10 μmol I3 prepared in Example 3.
[0060] Example 12: I4 catalyzes the polymerization of 1-octene to obtain L8. The preparation process is the same as in Example 9, except that the 10 μmol I1 prepared in Example 1 is replaced with the 10 μmol I4 prepared in Example 4.
[0061] Example 13: I4 catalyzes the polymerization of ethylene to obtain L9. The preparation process is the same as in Example 5, except that the container temperature is replaced with 20°C instead of 60°C.
[0062] Example 14: I4 catalyzes the polymerization of ethylene to obtain L10. The preparation process is the same as in Example 5, except that the container temperature is replaced with 80°C instead of 60°C.
[0063] Example 15: I4 catalyzes the polymerization of 1-octene to obtain L11. The preparation process is the same as in Example 9, except that the container temperature of 60°C is replaced with 40°C.
[0064] Example 16: I4 catalyzes the polymerization of 1-octene to obtain L12. The preparation process is the same as in Example 9, except that the container temperature of 60°C is replaced with 100°C.
[0065] Melting point was determined using a differential scanning calorimeter; molecular weight was determined by GPC using polystyrene as standard and trichlorobenzene as solvent at 150°C; degree of branching was determined by... 1 The total density of all short branches in polyethylene, measured by H NMR, is expressed as the number of branches per 1000 main chain carbon atoms ( / 1000C). These branches are mainly composed of methyl branches generated by the chain-walking mechanism. The results of the polymerization of ethylene and 1-octene catalyzed by the complexes prepared in Examples 1-4 are shown in Table 1 below: Table 1
[0066] As shown in Table 1, the complex in this application can catalyze the homopolymerization of ethylene to prepare polyethylene under certain conditions, with the highest activity reaching 5.06 × 10⁻⁶. 6 g•mol -1 •h -1 The degree of branching is 70~83 / 1000C; the highest number-average molecular weight is 1.46×10⁻⁶. 5 g / mol.
[0067] Examples 5-8 show that by changing the structure of the aniline substituent R, the polymerization activity of ethylene and the number-average molecular weight of the polymer both increase with the increase of the steric hindrance of the substituent, while the degree of branching gradually decreases. This directly proves that polymerization behavior can be directionally controlled through ligand structure design.
[0068] Examples 13-14 verified that the complex still has excellent thermal stability over a wide temperature range of 20-80°C.
[0069] The results of the polymerization of 1-octene catalyzed by the complexes prepared in Examples 1-4 are shown in Table 2 below: Table 2
[0070] As shown in Table 2, the complexes in this application can catalyze the preparation of 1-octene polymers under certain conditions, with the highest activity reaching 3.54 × 10⁻⁶. 5 g•mol -1 •h -1 The highest number-average molecular weight is 1.96 × 10⁻⁶. 5 g / mol.
[0071] Examples 9-12 show that complexes with different steric hindrances (I1-I4) can efficiently catalyze the polymerization of 1-octene. Among them, I1, with relatively small steric hindrance, exhibits the highest activity, while I4, with larger steric hindrance, can obtain the highest number-average molecular weight and a narrower molecular weight distribution. This directly proves that by adjusting the steric hindrance of the ligand substituents, it is possible to effectively control the molecular weight and distribution of the polymer while maintaining high activity.
[0072] Examples 13-14 verified that the complex exhibited excellent thermal stability in the catalytic preparation of 1-octene polymer over a wide temperature range of 40-100°C. As the temperature increased, the content of methyl branches increased while the content of hexyl branches decreased slightly, further demonstrating the catalyst's ability to regulate the polymer chain structure at different temperatures.
[0073] Comparative Example 1: Ethylene polymerization catalyzed by classic α-diimine nickel complexes For comparison, a classic α-diimine nickel comparative catalyst was synthesized (reported by the Brookhart team in J. Am. Chem. Soc., 1995, 117(23): 6414-6415), and the structure of the classic α-diimine nickel complex is shown in formula (D1): (D1) Preparation of D1: Under nitrogen protection, acenaphthene (0.91 g, 5 mmol) and 2,6-diisopropylaniline (1.95 g, 11 mmol) were dissolved in glacial acetic acid (7 mL) and reacted at 80 °C for 15 min. After cooling, the reaction solution was poured into ice water, filtered, and the precipitate was collected. The precipitate was washed with methanol and dried under vacuum to obtain the ligand. The ligand (0.40 mmol) was reacted with Ni(DME)Br2 (0.44 mmol) in 20 mL of dichloromethane and stirred at 25 °C for 6 h. After filtration, the filtrate was concentrated, and n-hexane was added to precipitate the solid. The solid was filtered and dried to obtain a dark red solid D1 (yield: 75%).
[0074] In a glove box under a nitrogen atmosphere, 28 mL of toluene and 1250 μmol of Et₂AlCl were added to an autoclave. The container was then connected to a high-pressure pipeline, and the pipeline was evacuated. The container temperature was set to 60 °C and maintained for 5 min. 2.5 μmol of D₁ prepared in Comparative Example 1 was dissolved in 2 mL of dichloromethane and injected into the autoclave using a syringe. Then, the ethylene valve was opened, ethylene was introduced into the autoclave, and the ethylene pressure was adjusted to 8 atm. The reaction was allowed to proceed for 15 min. After that, the reaction was stopped, the autoclave was opened, and ethanol was added to precipitate the solid. The mixture was filtered under reduced pressure and dried in a vacuum drying oven to obtain a white solid M₁.
[0075] Comparative Example 2: Polymerization of 1-octene catalyzed by classic α-diimine nickel complexes In a glove box under a nitrogen atmosphere, 10 mL of toluene, 5000 μmol of Et₂AlCl, and 2.24 g of 1-octene were added to an autoclave. The container was then connected to a high-pressure pipeline and evacuated. The container temperature was set to 60 °C and maintained for 5 min. 10 μmol of D₁ prepared in Comparative Example 1 was dissolved in 2 mL of dichloromethane and added to the autoclave. The reaction was allowed to proceed for 30 min. The autoclave was then opened, and ethanol was added to precipitate the solid. The mixture was filtered under reduced pressure to obtain M₂.
[0076] The properties of the complexes of this invention and the comparative classical complexes for catalytic ethylene polymerization are shown in Table 3.
[0077] Table 3
[0078] As shown in Table 3, the ethylene polymerization activity of I3 is much greater than that of D1, indicating that the bis(4-fluorophenyl)methyl structure introduced at the 4-position of the ligand in this invention can greatly improve the catalytic efficiency.
[0079] Example 7 achieved a higher number-average molecular weight while having a lower degree of branching, demonstrating that the complex of the present invention can more effectively inhibit chain walk and promote chain growth.
[0080] The properties of the complexes of this invention and the comparative classical complexes for catalyzing the polymerization of 1-octene are shown in Table 4.
[0081] Table 4
[0082] As shown in Table 4, when catalyzing long-chain α-olefins (1-octene), the activity of I3 is nearly 4 times that of D1, indicating that the complex of the present invention can greatly improve the catalytic efficiency of long-chain α-olefins.
[0083] The polymer obtained in Example 11 contains abundant hexyl branches, while the product of D1 contains very few hexyl branches. This proves that the complex of the present invention can efficiently promote the insertion of long-chain monomers into the polymer chain, while classical catalysts are very weak in this respect and can only produce oligomers.
[0084] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.
Claims
1. An α-diimine nickel complex, characterized in that, The structure of the complex is shown in formula (I): （I） In formula (I), R is selected from one of the substituted phenyl, isopropyl, alkyl, fluorine, chlorine, bromine, iodine, nitro, hydroxyl, and silyl groups from C1 to C20; wherein the R parts can also bond to each other to form a ring.
2. A method for preparing the α-diimine nickel complex as described in claim 1, characterized in that, The synthesis process of the complex is as follows: (1) Dissolve acenaphthene in acetonitrile, heat and stir for 15 min to form a reaction mixture, then slowly add glacial acetic acid to the mixture, followed by aniline compounds, wherein the weight ratio of acenaphthene, acetonitrile and glacial acetic acid is 1:(15.2~16):(8~8.2), and continue the reaction for 4~10 h to obtain the ligand; (2) Under an inert gas atmosphere, the ligand is dissolved in a good solvent, Ni(DME)Br2 is added to react, and after concentration, a poor solvent is added to recrystallize to obtain the α-diimine nickel complex.
3. The method for preparing an α-diimine nickel complex according to claim 2, characterized in that, The structure of the aniline compounds in step (1) is as follows: R is selected from one of the following C1~C20 substituted phenyl, isopropyl, alkyl, fluorine, chlorine, bromine, iodine, nitro, hydroxyl, and silyl groups; wherein the R moieties can also bond to each other to form a ring.
4. The method for preparing an α-diimine nickel complex according to claim 2, characterized in that, The structure of the ligand in step (1) is shown in equation (II) below: (II) In formula (II), R is selected from one of the substituted phenyl, isopropyl, alkyl, fluorine, chlorine, bromine, iodine, nitro, hydroxyl, and silyl groups from C1 to C20; wherein the R parts can also bond to each other to form a ring.
5. The method for preparing an α-diimine nickel complex according to claim 2, characterized in that, In step (1), the molar ratio of acenaphthene to aniline compounds is 1:(2~2.5).
6. The method for preparing an α-diimine nickel complex according to claim 2, characterized in that, In step (2), the molar ratio of ligand to Ni(DME)Br2 is 1:(1.1~1.5).
7. The method for preparing an α-diimine nickel complex according to claim 2, characterized in that, The good solvent mentioned in step (2) is one of dichloromethane, toluene, xylene, and trichlorobenzene.
8. The method for preparing an α-diimine nickel complex according to claim 2, characterized in that, The undesirable solvent mentioned in step (2) is one of diethyl ether, petroleum ether, n-hexane, n-pentane, and n-heptane.
9. The application of the α-diimine nickel complex according to claim 1 or 2, characterized in that, The α-diimine nickel complex can initiate homogeneous polymerization of ethylene and polymerization of long-chain α-olefins as a single component.
10. The application according to claim 9, characterized in that, The long-chain α-olefin is one or a mixture of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 1-decene, 1-dodecene, and 1-octadecene.