Tridentate pyridyl amino hafnium complexes, methods of making and using the same

Abstract

The application provides a tridentate pyridyl amino hafnium complex and a preparation method and application thereof, and belongs to the technical field of catalyst preparation, wherein the tridentate pyridyl amino hafnium complex has a structure as shown in formula (I): in formula (I), R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 are independently selected from hydrogen, a C1-C6 aliphatic hydrocarbon group, halogen, a C1-C6 substituted aliphatic hydrocarbon group, a phenyl group, a substituted phenyl group, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 are the same or different.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, and particularly relates to a tridentate pyridine aminohafnium complex, its preparation method and application. Background Technology

[0002] Polyolefins, as a landmark product of modern chemical industry, have penetrated into all aspects of human life. As the core driving force in the polyolefin field, the research of polyolefin catalysts has always been a focus of researchers. Starting with the great discovery of Ziegler-Natta, widespread commercial demand stimulated the vigorous development of the catalyst field. Homogeneous metallocene catalysts (transition metal-organic complexes formed by the coordination of transition metals with pentane rings) were another milestone discovery. The rapid development of homogeneous metallocene catalysts benefited from their well-defined structures, enabling polyolefin products with narrow molecular weight distributions to enter human life. Furthermore, these catalysts can achieve stereoconfiguration control in propylene polymerization. Dow Chemical and ExxonMobil jointly discovered restricted geometry catalysts (CGCs), and the commercial application of these catalysts has progressed rapidly under their impetus. For example, CGCs are used in the copolymerization of ethylene with α-olefins (usually 1-octene or 1-hexene). Subsequently, bis(phenoxy-imine) pre-transition metal complexes (FI catalysts) were developed and commercialized, making the production of block copolymers and chain-end functionalization possible. By using a highly efficient copolymer (pyridineamino) hafnium catalyst, Dow Chemical has realized the concept of chain shuttle polymerization and commercialized it.

[0003] Polyolefins have a wide range of applications and numerous products due to the addition of functional comonomers during polymerization, which alters the properties of the polymer and changes its elasticity. Commercially available pyridine-amino-hafnium catalysts have demonstrated excellent performance; for example, bidentate pyridine-amino-hafnium catalysts have been shown to have high activity and high-temperature resistance. However, these catalysts use naphthalene-containing ligands in their synthesis, resulting in high costs for the coupling reaction of pyridine-amino compounds. Bidentate pyridine-amino ligands without the naphthalene moiety are easier to prepare and less expensive than known naphthalene-containing parent ligands. However, the corresponding hafnium catalysts are spatially more open, which may facilitate chain transfer reactions, leading to lower molecular weight polymer products. Therefore, developing new pyridine-amino-hafnium catalysts to obtain higher molecular weight polymer products during catalytic processes is a pressing issue. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a tridentate pyridine aminohafnium complex, its preparation method, and its applications, aiming to at least partially solve the above-mentioned technical problems.

[0005] Specifically, the technical solution provided by this invention is as follows:

[0006] As a first aspect of the present invention, a tridentate pyridine aminohafnium complex is provided, having the structure shown in formula (I):

[0007]

[0008] In equation (I), R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 Independently selected from hydrogen, C1-C6 aliphatic hydrocarbon groups, halogens, C1-C6 substituted aliphatic hydrocarbon groups, phenyl groups, substituted phenyl groups, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 It can be either the same or different.

[0009] As a second aspect of the present invention, a method for preparing a tridentate pyridine aminohafnium complex is provided, comprising:

[0010] In an anhydrous and oxygen-free organic solvent, the bidentate pyridine amino hafnium compound reacts with a ligand containing a phenolic hydroxyl group to obtain the above-mentioned tridentate pyridine amino hafnium complex.

[0011] Among them, the ligand containing the phenolic hydroxyl group has the structure shown in formula (II):

[0012]

[0013] In equation (II), R7, R8, R9, and R 10 R 11 It has the same definition as the above-mentioned tridentate pyridine aminohafnium complexes.

[0014] As a third aspect of the invention, an application of the above-described tridentate pyridine aminohafnium complex as a catalyst in an olefin polymerization reaction is provided, wherein the olefin polymerization reaction includes: homopolymerization and copolymerization.

[0015] Based on the above technical solution, the present invention provides a tridentate pyridine aminohafnium complex, its preparation method and application, which includes at least one of the following beneficial effects:

[0016] (1) In the embodiments of the present invention, based on the original structure of the bidentate pyridine amino hafnium compound, the high activity of hafnium methyl is utilized to introduce a highly active and sterically hindered phenolic hydroxyl ligand structure and react it with hafnium methyl to form a tridentent pyridine amino hafnium complex. The tridentent pyridine amino hafnium complex has a large steric hindrance, which can inhibit chain transfer reaction, thereby enabling the tridentent pyridine amino hafnium complex to increase the molecular weight of polymer products during application.

[0017] (2) In the embodiments of the present invention, a simple one-step reaction is used to utilize the high activity of hafnium methyl in the bidentate pyridine amino hafnium compound to react with the hydroxyl group in the substituted phenolic hydroxyl group small ligand with high activity to obtain a tridentate pyridine amino hafnium complex with large steric hindrance. The process is simple and easy to control. Attached Figure Description

[0018] Figure 1 This is the 1H NMR spectrum of the complex in Example 4 of this invention;

[0019] Figure 2 This is the 1H NMR spectrum of the complex in Example 5 of this invention;

[0020] Figure 3 The high-temperature carbon NMR spectrum of the ethylene-1-octene copolymer obtained in Project 2 of this invention is shown.

[0021] Figure 4 This is the high-temperature hydrogen NMR spectrum of the ethylene-norbornene copolymer obtained in Project 4 of this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0023] In related technologies, adding functional comonomers during the polymerization of polyolefins can improve the properties of the polymer. For example, adding functional comonomers can alter the properties of the polymer to a certain extent. For instance, copolymers of ethylene and norbornene are called cyclic monomer copolymers (COCs), and due to their high light transmittance and stability, they are widely used in biomedical fields and some optical facilities. Ordinary linear polyethylene, although having high crystallinity, has poor elasticity. By incorporating a certain amount of α-olefins into the polymerization system, the polymer's regularity decreases, crystallinity decreases, and thus elasticity is improved. These copolymers of ethylene and α-olefins are called polyolefin elastomers (POEs). Ethylene-propylene rubber (EPR) has a huge annual production volume and is a well-known non-tire elastomer. As a widely used synthetic rubber, it is obtained by copolymerizing ethylene and propylene or by ternary copolymerizing them with dienes.

[0024] To effectively synthesize polyolefin elastomer materials and address the issues of more open steric space and easier chain transfer reactions in bidentate pyridine amino hafnium compounds in related technologies, this invention proposes a method that utilizes the active hafnium methyl group in bidentate pyridine amino hafnium compounds to react with the hydroxyl group in phenolic hydroxyl groups, which have high activity and greater steric hindrance, to form a tridentate pyridine amino hafnium complex. The resulting hafnium complex has greater steric hindrance, which can suppress chain transfer reactions and increase the molecular weight of the polymer.

[0025] Specifically, the present invention provides a tridentate pyridine aminohafnium complex having the structure shown in formula (I):

[0026] In equation (I), R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 Independently selected from hydrogen, C1-C6 aliphatic hydrocarbon groups, halogens, C1-C6 substituted aliphatic hydrocarbon groups, phenyl groups, substituted phenyl groups, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 It can be either the same or different.

[0027] According to embodiments of the present invention, the aliphatic hydrocarbon groups of C1-C6 are selected from any one of propyl, isopropyl, butyl, tert-butyl, methyl, and ethyl, and the substituents are selected from any one of hydrogen and fluorine.

[0028] According to an embodiment of the present invention, wherein R1 and R2, R4 and R6, R7 and R8, R9 and R 10 At least one pair of them has the same group.

[0029] According to an embodiment of the present invention, a complex having the structure shown in formula (I) has one of the following structures:

[0030] iPr is isopropyl, tBu is tert-butyl;

[0031] iPr is isopropyl, tBu is tert-butyl;

[0032] iPr is isopropyl, tBu is tert-butyl;

[0033] tBu is tert-butyl;

[0034] tBu is tert-butyl;

[0035] tBu is tert-butyl.

[0036] In embodiments of the present invention, it is preferable to use some substituents with greater steric hindrance to replace the hydrogen on the benzene ring in the bidentate pyridine amino hafnium compound, thereby increasing the steric hindrance of the tridentate pyridine amino hafnium complex.

[0037] As a second aspect of the present invention, a method for preparing a tridentate pyridine aminohafnium complex is also provided, comprising: reacting a bidentate pyridine aminohafnium compound with a phenolic hydroxyl-containing ligand in an anhydrous and oxygen-free organic solvent to obtain a tridentate pyridine aminohafnium complex; wherein the phenolic hydroxyl-containing ligand has a structure as shown in formula (II):

[0038] In equation (II), R7, R8, R9, and R 10 R 11 Compounds R7, R8, R9, and R1 in the above-described embodiment (I) have the same composition as compounds R7, R8, R9, and R1. 10 R 11 They have the same definition.

[0039] Specifically, the principle for preparing the above-mentioned tridentate pyridine aminohafnium complex catalyst is as follows:

[0040]

[0041] The molar ratio of the bidentate pyridine aminohafnium compound to the phenolic hydroxyl-containing ligand is 1:1.01–1.05. Using an excess of the phenolic hydroxyl-containing ligand ensures sufficient reaction between the bidentate pyridine aminohafnium compound and the phenolic hydroxyl-containing ligand. The reaction temperature is 35–50°C, preferably 40°C; the reaction time is 1–50 hours, preferably 2 hours. The organic solvent is selected from at least one of tetrahydrofuran, petroleum ether, toluene, benzene, dichloromethane, tetrachloromethane, diethyl ether, 2,4-dioxane, and 1,2-dichloroethane.

[0042] For example, in anhydrous and oxygen-free toluene, at 40°C, the active hafnium methyl group in a reactive bidentate pyridine amino hafnium compound reacts with a highly reactive phenolic hydroxyl group for 2 hours to obtain a tridentate pyridine amino hafnium complex.

[0043] According to embodiments of the present invention, the present invention also provides the application of tridentate pyridine aminohafnium complexes as catalysts in olefin polymerization reactions, wherein the olefin polymerization reactions include homopolymerization and copolymerization.

[0044] In embodiments of the present invention, a tridentate pyridine amino hafnium complex with large steric hindrance is used as a catalyst to catalyze the olefin polymerization reaction, which can suppress chain transfer reaction and thus help to increase the molecular weight of the olefin polymerization product.

[0045] According to an embodiment of the present invention, the tridentate pyridine aminohafnium complex as a catalyst for catalyzing the homopolymerization of olefins includes: homogeneous polymerization of C2-C8 low-carbon olefins, wherein the C2-C8 low-carbon olefins are selected from any one of ethylene, propylene, butene, pentene, and hexene.

[0046] The specific process of the tridentate pyridine aminohafnium complex as a catalyst for the homopolymerization of low-carbon-number olefins is as follows:

[0047] Under an inert atmosphere in a glove box, 48 mL of organic solvent (n-heptane) and nitrogen-containing borane (PhNH(CH3)2][B(C6F5)4) were added to a 350 mL autoclave (equipped with a magnetic stirrer, oil bath heating device, and thermometer). The container was connected to a high-pressure pipeline and the pipeline was evacuated. The autoclave was then kept at 1-150 °C for 15 min. An organic solution containing the complex of formula (I) (n-heptane) and the scavenger triisobutylaluminum were then injected into the polymerization system. The molar ratio of triisobutylaluminum to the hafnium complex was 1:1-10000, and the molar ratio of borane to the hafnium complex was 1:1-10000. The valves were closed, the ethylene pressure was adjusted to 8 atm, and the reaction was allowed to proceed for 10 min. The reaction was then stopped, the autoclave was opened, and ethanol was added to precipitate the solid. The solid was filtered under reduced pressure and dried in a vacuum drying oven to obtain a white solid, a low-carbon olefin polymer.

[0048] According to an embodiment of the present invention, the tridentate pyridine aminohafnium catalyst is used as a catalyst to catalyze the copolymerization reaction of olefins, including the copolymerization reaction of C2-C8 low carbon number olefins with 1-octene or norbornene, wherein the C2-C8 low carbon number olefins are selected from any one of ethylene, propylene, butene, pentene, and hexene.

[0049] According to an embodiment of the present invention, a method for preparing a copolymer of C2-C8 low carbon number olefins and 1-octene includes: copolymerizing C2-C8 low carbon number olefins with 1-octene or norbornene under the action of a tridentate pyridine amino hafnium complex with the structure shown in formula (I) above, to obtain a copolymer.

[0050] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a bidentate pyridine aminohafnium complex, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0051] Example

[0052] The following examples illustrate the specific content of the present invention. The data provided include methods for synthesizing metal compounds, polymerizing or copolymerizing ethylene, wherein the synthesis of complexes and polymerization processes are carried out under anhydrous and oxygen-free conditions. All sensitive substances are stored in glove boxes, all solvents are strictly dried and dehydrated, ethylene gas is purified by dehydration and deoxygenation column chromatography, and 1-octene is purified by dehydration, deoxygenation, and vacuum distillation. Unless otherwise specified, all raw materials are used directly after purchase.

[0053] Silica gel columns were made of 200-300 mesh silica gel, and 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 columns, HR2 and HR4, oven temperature 45℃, using Water 1515 and Water 2414 pumps. The mobile phase was tetrahydrofuran, flow rate was 1.0 mL / min, and polydisperse polystyrene was used as the standard).

[0054] Example 1

[0055] The structure of the di-tert-butyl-4-methylphenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-diisopropylaniline hafnium complex is shown in formula (I01), and its preparation process is as follows:

[0056] iPr is isopropyl; tBu is tert-butyl.

[0057] Under an inert gas atmosphere at 40 °C, di-tert-butyl-4-methylphenol (0.22 g, 0.1 mmol) was dissolved in 5 mL of toluene and slowly added dropwise to 40 mL of anhydrous toluene solution containing N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-diisopropylaniline hafnium complex (0.68 g, 0.1 mmol) under stirring. The mixture was stirred at the same temperature for 2 hours. After the reaction was completed, the solvent was removed to obtain the di-tert-butyl-4-methylphenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-diisopropylaniline hafnium complex.

[0058] 1 H NMR (400MHz, Benzene-d6): δ8.42 (m, 1H py-H), 6.44-7.19(m, 11H), 5.89(s, 1H, py-CH-N), 3.81(setp, 1H, J=6.8Hz, CH(CH3)2), 3.39(setp, 1H, J=6.8Hz, CH(CH3)2), 1.40-1.96(m, 12H , CH(CH3)2), 2.18(s,3H,aryl-CH3)1.23-1.32(s,18H,aryl-C(CH3)3), 1.03(s,18H,aryl-C(CH3)3), 0.95(s,3H,Hf-Me), 0.38(s,3H,Hf-Me).

[0059] 13C NMR (101MHz, Benzene-d6): δ167.82, 158.84149.27, 143.53, 142.44, 137.55, 128.1 1, 124.48, 123.60, 121.18, 80.87, 55.68, 33.64, 30.33, 26.96, 25.56, 23.25, 20.32.

[0060] Example 2

[0061] The structure of the 2,6-difluorophenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-diisopropylaniline hafnium complex is shown in formula (I02), and its preparation process is as follows:

[0062] iPr is isopropyl; tBu is tert-butyl.

[0063] Under an inert gas atmosphere at 40 °C, 2,6-difluorophenol (0.13 g, 0.1 mmol) was dissolved in 5 mL of toluene and slowly added dropwise to 40 mL of anhydrous toluene solution containing N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-diisopropylaniline hafnium complex (0.68 g, 0.1 mmol) under stirring. The mixture was stirred at the same temperature for 2 hours. After the reaction was completed, the solvent was removed to obtain 2,6-difluorophenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-diisopropylaniline hafnium complex.

[0064] 1 H NMR (400MHz, Benzene-d6): δ8.23 (m, 1H py-H), 5.96-7.12 (m, 12H), 5.65 (s, 1H, py-CH-N), 3.38 (setp, 1H, J=6.8Hz, CH(CH3)2), 3.05 (setp, 1H, J=6.8Hz, CH(CH3)2), 1.0 5-1.25(m, 12H, CH(CH3)2), 0.98(s, 18H, aryl-C(CH3)3), 1.03(s, 18H, aryl-C(CH3)3), 0.94(s, 3H, Hf-Me), 0.66(s, 3H, Hf-Me).

[0065] 13C NMR (101MHz, Benzene-d6): δ166.54, 155.60, 153.16, 145.36, 143.35, 141.44, 128.12, 124.48, 123. 14, 124.43, 150.51, 117.08, 110.09, 79.75, 47.30, 33.48, 30.31, 27.33, 24.24, 24.20, 22.9, 120.24.

[0066] Example 3

[0067] The structural formula of the methylphenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-diisopropylaniline hafnium complex is shown in formula (I03), and its preparation process is as follows:

[0068] iPr is isopropyl; tBu is tert-butyl.

[0069] Under an inert gas atmosphere at 40 °C, p-methylphenol (0.22 g, 0.2 mmol) was dissolved in 5 mL of toluene and slowly added dropwise to 40 mL of anhydrous toluene solution containing N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-diisopropylaniline hafnium complex (1.36 g, 0.2 mmol) under stirring. The mixture was stirred at the same temperature for 2 hours. After the reaction was completed, the solvent was removed to obtain p-methylphenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-diisopropylaniline hafnium complex.

[0070] 1 H NMR (400MHz, Benzene-d6): δ8.35 (m, 1H py-H), 6.14-7.16(m, 12H), 5.67(s, 1H, py-CH-N), 3.28(setp, 1H, J=6.8Hz, CH(CH3)2), 3.01(setp, 1H, J=6.8Hz, CH(CH3)2), 1.92(s, 3H, ary l-CH3), 1.10-1.28(m, 12H, CH(CH3)2), 0.98(s, 18H, aryl-C(CH3)3), 1.03(s, 18H, aryl-C(CH3)3), 0.53(s, 3H, Hf-Me), 0.27(s, 3H, Hf-Me).

[0071] Example 4

[0072] The structure of the di-tert-butyl-4-methylphenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-dimethylaniline hafnium complex is shown in formula (I04), and its preparation process is as follows:

[0073] tBu is tert-butyl.

[0074] Under an inert gas atmosphere at 40°C, di-tert-butyl-4-methylphenol (0.22 g, 0.1 mmol) was dissolved in 5 mL of toluene and slowly added dropwise to 40 mL of anhydrous toluene solution containing N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-dimethylaniline hafnium complex (0.62 g, 0.1 mmol) under stirring. The mixture was stirred at the same temperature for 2 hours. After the reaction was completed, the solvent was removed to obtain the di-tert-butyl-4-methylphenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-dimethylaniline hafnium complex. The 1H NMR spectrum of the hafnium complex in Example 4 is shown below. Figure 1 As shown.

[0075] 1 H NMR (400MHz, Benzene-d6): δ8.44 (m, 1H py-H), 6.51-7.39(m, 12H), 5.61(s, 1H, py-CH-N), 2.30(s, 6H, aryl-CH3), 2.25(s, 3H, ary l-CH3), 1.38(s, 18H, aryl-C(CH3)3), 1.24(s, 18H, aryl-C(CH3)3), 0.30(s, 3H, Hf-Me2).

[0076] Example 5

[0077] The structure of the 2,6-difluorophenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-dimethylaniline hafnium complex is shown in formula (I05), and its specific preparation process is as follows:

[0078] tBu is tert-butyl.

[0079] Under an inert gas atmosphere at 40°C, 0.13 g (0.1 mmol) of 2,6-difluorophenol was dissolved in 5 mL of toluene and slowly added dropwise to 40 mL of anhydrous toluene solution containing N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-dimethylaniline hafnium complex (0.62 g, 0.1 mmol) under stirring. The mixture was stirred at the same temperature for 2 hours. After the reaction was completed, the solvent was removed to obtain the 2,6-difluorophenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-dimethylaniline hafnium complex. The 1H NMR spectrum of the hafnium complex in Example 5 is shown below. Figure 2 As shown.

[0080] 1 H NMR (400MHz, Benzene-d6): δ8.43 (m, 1H py-H), 6.18-7.33(m, 12H), 5.77(s, 1H, py-CH-N), 2.45(s, 3H, aryl-CH3), 1.57(s, 3H, aryl-CH3), 1.19(s, 18H, aryl-C(CH3)3), 0.73(s, 3H, Hf-Me), 0.54

[0081] Example 6

[0082] The structure of the methylphenol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-dimethylaniline hafnium complex is shown in formula (I06), and the specific preparation process is as follows:

[0083] tBu is tert-butyl;

[0084] Under an inert gas atmosphere at 40 °C, p-cresol (0.22 g, 0.2 mmol) was dissolved in 5 mL of toluene and slowly added dropwise to 40 mL of anhydrous toluene solution containing N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-dimethylaniline hafnium complex (1.24 g, 0.2 mmol) under stirring. The mixture was stirred at the same temperature for 2 hours. After the reaction was completed, the solvent was removed to obtain p-cresol-substituted N-((3,5-di-tert-butylphenyl)(pyridin-2-yl)methyl)-2,6-dimethylaniline hafnium complex.

[0085] 1H NMR (400MHz, Benzene-d6): δ7.33 (m, 1H py-H), 6.52-7.13(m, 12H), 5.73(s, 1H, py-CH-N), 2.38(s, 3H, aryl-CH3), 2.06(s, 3H, aryl-CH3 ), 1.54(s, 3H, aryl-CH3), 1.16(s, 18H, aryl-C(CH3)3), 0.29(s, 4H, Hf-Me), 0.16(s, 2H, Hf-Me).

[0086] Application examples

[0087] Application Example 1: Catalytic Ethylene Polymerization

[0088] In a glove box under a nitrogen atmosphere, 48 mL of n-heptane and 1.5 equivalents of [PhNH(CH3)2][B(C6F5)4] were added to a 350 mL autoclave (equipped with a magnetic stirrer, oil bath heating device, and thermometer). The container was connected to a high-pressure pipeline and the pipeline was evacuated. The container temperature was set to 150 °C and maintained for 15 minutes. The complex catalysts of Examples 1-6 dissolved in 2 mL of n-heptane, along with triisobutylaluminum as a scavenger, were injected into the polymerization system using a syringe. The valve was closed, the ethylene pressure was adjusted to 8 atm, and the reaction was allowed to proceed for 10 minutes. The reaction was stopped, the reactor was opened, 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. The results of the hafnium complex catalysts prepared in Examples 1-6 on the polymerization of ethylene are shown in Table 1.

[0089] Table 1. Results of ethylene polymerization using hafnium complex catalysts prepared in Examples 1-6.

[0090]

[0091] a Polymerization conditions: Hafnium complex = 5 μmol; n-Heptane = 50 mL; Ethylene = 8 atm or 20 atm; Time = 10 min; b Activity=10 6 g·mol -1 ·h -1 ; c Melting point was determined using a differential scanning calorimeter. d Weight-average molecular weight = 10 4 gmol -1 The molecular weight was determined by GPC using polystyrene as the standard and trichlorobenzene as the solvent at 150 degrees Celsius.

[0092] As can be seen from Table 1 above, the complex catalysts of Examples 1-6 provided by the present invention catalyze the polymerization of ethylene, and the obtained polymers have high weight-average molecular weights.

[0093] Application Example 2: Catalytic copolymerization of ethylene and 1-octene

[0094] A 350 mL thick-walled glass pressure vessel was loaded with n-heptane, the required amount of 1-octene, 1.5 equivalents of [PhNH(CH3)2][B(C6F5)4], and a magnetic stir bar glove box. The total liquid volume was 48 mL. The pressure vessel was connected to a high-pressure line, and the solution was degassed. The vessel was heated to 150 °C using an oil bath and allowed to equilibrate for 10 minutes. 5 μmol of catalyst and 5 equivalents of triisobutylaluminum were dissolved in 2 mL of n-heptane and then injected into the polymerization system via a syringe. The reactor was pressurized under rapid stirring and maintained at the required ethylene pressure. After 10 minutes, the pressure vessel was vented, and a 10% hydrochloric acid methanol solution was added to the polymerization mixture to precipitate the polymer. The precipitated polymer was stirred for several hours, filtered, washed with methanol, and collected. It was then dried overnight at 45 °C under high vacuum to constant weight. The results of the hafnium complex catalysts prepared in Examples 1–6 for the copolymerization of ethylene and 1-octene are shown in Table 2.

[0095] Table 2. Results of the copolymerization of ethylene and 1-octene using hafnium complex catalysts prepared in Examples 1-6.

[0096]

[0097] a Catalyst = 5 μmol; t = 10 min; 1-octene = 0.5 mol / L; heptane = 50 mL; [PhNH(CH3)2][B(C6F5)4] = 1.5 equivalents, iBu3Al = 5 equivalents; b Total activity (10) 6 g mol -1 h -1 ): Determined by the quality of the polymer product. c Determined by differential scanning calorimetry. d Determined by carbon NMR spectroscopy analysis. e Weight-average molecular weight: 10 4 g mol -1 The weight-average molecular weight and molecular weight distribution were determined by GPC in trichlorobenzene at 150 °C.

[0098] As shown in Table 2, the hafnium complex catalyst provided by the present invention can catalyze the copolymerization reaction of ethylene and 1-octene, and the obtained copolymer has a high weight-average molecular weight.

[0099] Figure 3 The high-temperature carbon NMR spectrum of the ethylene-1-octene copolymer obtained in Project 2 of this invention is shown below. 13 (C NMR).

[0100] Application Example 3: Catalytic copolymerization of ethylene and norbornene

[0101] A 350 mL thick-walled glass pressure vessel was loaded with n-heptane, the required amount of norbornene, 1.5 equivalents of [PhN(CH3)2][B(C6F5)4], and a magnetic stir bar glove box. The total liquid volume was 48 mL. The pressure vessel was connected to a high-pressure line, and the solution was degassed. The vessel was heated to a specific temperature between 80 and 150 °C using an oil bath and allowed to equilibrate for 10 minutes. 5 μmol of catalyst and 5 equivalents of triisobutylaluminum were dissolved in 2 mL of n-heptane and then injected into the polymerization system via a syringe. The reactor was pressurized under rapid stirring and maintained at the required ethylene pressure. After 10 minutes, the pressure vessel was vented, and a 10% hydrochloric acid methanol solution was added to the polymerization mixture to precipitate the polymer. The precipitated polymer was stirred for several hours, filtered, washed with methanol, and collected. It was then dried overnight under high vacuum at 45 °C to constant weight. The results of copolymerization of ethylene and norbornene with the catalysts prepared in Examples 1–6 are shown in Table 3.

[0102] Table 3 shows the results of copolymerization of ethylene and norbornene with hafnium complexes prepared in Examples 1-6.

[0103]

[0104] a Catalyst = 5 μmol; t = 10 min; heptane = 50 mL; [PhNH(CH3)2][B(C6F5)4] = 1.5 equivalents; triisobutylaluminum = 5 equivalents; pressure of the polymerization unit P = 8 atm; b Total activity (10) 6 g mol -1 h -1 ): Determined by the quality of the polymer product. c The glass transition temperature was determined by differential scanning calorimetry. d Determined by proton nuclear magnetic resonance spectroscopy. e Weight-average molecular weight: 10 4 g mol -1 The weight-average molecular weight and molecular weight distribution were determined by GPC in trichlorobenzene at 150 °C.

[0105] Figure 4 The high-temperature 1H NMR spectrum of the ethylene-norbornene copolymer obtained in Project 4 of this invention is shown below. 1 H NMR).

[0106] As can be seen from the above application examples, the present invention provides a tridentate pyridine aminohafnium complex, its preparation method, and its applications. This catalyst has the structure shown in formula (I) and can catalyze the polymerization or copolymerization of C2-C8 low-carbon olefins. It exhibits high thermal stability and activity for the polymerization of C2-C8 low-carbon olefins. For the copolymerization of C2-C8 low-carbon olefins with 1-octene, copolymers with polyolefin elastomer properties and high insertion ratios are produced, such as copolymers of ethylene and 1-octene, i.e., polyolefin elastomers (POE). For the copolymerization of C2-C8 low-carbon olefins with norbornene, cyclic monomer copolymers are produced with high molecular weight and considerable cyclic monomer insertion, such as copolymers of ethylene and norbornene (COC). In the catalytic homopolymerization of ethylene at 150°C, the activity of this hafnium complex catalyst reaches a maximum of 3.07 × 10⁻⁶. 6 g of PE (mol of Hf) -1 h -1 The highest weight-average molecular weight was 648,000 g / mol with a unimodal distribution and a molecular weight distribution of 2.1. In the reaction of ethylene with 1-octene catalyzed by this hafnium complex catalyst, the highest weight-average molecular weight of the obtained copolymer was 811,000 g / mol, with a highest 1-octene insertion ratio of 12.5%. In the reaction of ethylene with norbornene catalyzed by this hafnium complex catalyst, the highest weight-average molecular weight of the obtained copolymer was 2,987,000 g / mol, with a highest norbornene insertion ratio of 34.1%.

[0107] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tridentate pyridine aminohafnium complex having the structure shown in formula (I): Equation (I); In equation (I), R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 Independently selected from hydrogen, C1-C6 aliphatic hydrocarbon groups, halogens, phenyl groups, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 It can be either the same or different.

2. The complex according to claim 1, wherein, R1 and R2, R4 and R6, R7 and R8, R9 and R 10 At least one pair of them has the same group.

3. The complex according to claim 1 or 2, wherein, The complex has one of the following structures: Formula (I01), iPr is isopropyl, and tBu is tert-butyl; Formula (I02), iPr is isopropyl, and tBu is tert-butyl; Formula (I03), iPr is isopropyl, and tBu is tert-butyl; Equation (I04), tBu is tert-butyl; Equation (I05), tBu is tert-butyl; In equation (I06), tBu is tert-butyl.

4. A method for preparing tridentate pyridine aminohafnium complexes, comprising: In an anhydrous and oxygen-free organic solvent, the bidentate pyridine amino hafnium compound is reacted with a ligand containing a phenolic hydroxyl group to obtain the tridentate pyridine amino hafnium complex as described in any one of claims 1-3; The ligand containing the phenolic hydroxyl group has a structure as shown in formula (II): Formula (II); In equation (II), R7, R8, R9, and R 10 R 11 It has the definition as described in any one of claims 1-3.

5. The method according to claim 4, wherein, The method includes: 。 6. The method according to claim 4 or 5, wherein, The molar ratio of the bidentate pyridine aminohafnium compound to the phenolic hydroxyl-containing ligand is 1:1.01~1.05, the reaction temperature is 35-50℃, and the reaction time is 1-50 hours.

7. The method according to claim 4 or 5, wherein, The organic solvent is selected from at least one of tetrahydrofuran, petroleum ether, toluene, benzene, dichloromethane, tetrachloromethane, diethyl ether, and 1,2-dichloroethane.

8. The use of the tridentate pyridine aminohafnium complex according to any one of claims 1-3 as a catalyst in olefin polymerization, wherein, The olefin polymerization reactions are: homopolymerization and copolymerization.

9. The application according to claim 8, wherein, The homopolymerization reaction is a homogeneous polymerization reaction of C2-C8 low-carbon olefins.

10. The application according to claim 8, wherein, The copolymerization reaction is a copolymerization reaction of C2-C8 low carbon number olefins with 1-octene or norbornene.

Images