A dinuclear vanadium catalyst containing a bis-NHC ligand, its preparation method and use

Abstract

The present invention provides a dinuclear vanadium catalyst containing a bis-NHC ligand, its preparation method and uses, and specifically relates to the fields of organometallic catalysts for olefin polymerization and olefin coordination polymerization. The general structural formula of the dinuclear vanadium catalyst containing a bis-NHC ligand is shown as follows: #imgabs0#. In the general structural formula, the structural formula of Linker is: #imgabs1# or #imgabs2# or #imgabs3#; wherein, R1, R2, R3, R4, R5 are each independently selected from any one of a hydrogen atom, an alkyl group, a fluorine atom, and a phenyl group, and R´1, R´2, R´3, R´4, R´5 correspond to R1, R2, R3, R4, R5 one by one. The dinuclear vanadium catalyst containing a bis-NHC ligand of the present invention is used for catalyzing the homopolymerization of ethylene and its copolymerization with polar olefin monomers. By introducing an NHC ligand with strong electron-donating ability and relatively high thermal stability, a stable compound can be formed with transition metal vanadium, so that it is not easily decomposed during the catalytic reaction process and is not easily poisoned and inactivated by polar monomers, thereby improving the catalytic efficiency and obtaining functionalized polyolefin materials.

Description

Technical Field

[0001] The present invention relates to the fields of organometallic catalysts for olefin polymerization and olefin coordination polymerization, and particularly relates to a dinuclear vanadium catalyst containing a bis-NHC ligand, a preparation method thereof, and uses thereof. Background Art

[0002] Polyolefin materials account for approximately 50% of polymer synthetic materials, and their importance is reflected in many fields of daily life. Due to the inertness of chemical bonds, non-functionalized polyolefin materials exhibit great advantages in terms of solvent corrosion resistance and thermal stability. However, at the same time, they also have limitations in many aspects, such as poor adhesion, dyeability, rheology, and blendability. In order to broaden the application scope of polyolefin materials, the research on functionalized polyolefin materials has always been one of the directions of concern and exploration in both the academic and industrial fields. Introducing polar functional groups into polyolefin materials mainly through high-temperature and high-pressure free radical polymerization, ionic polymerization, or post-polymerization modification and other methods. The above methods generally have relatively harsh conditions and relatively poor controllability, and it is difficult to achieve the regulation at the molecular level of the polymer. In contrast, the process of directly copolymerizing olefins with polar monomers using metal catalysis to prepare functionalized polyolefin materials is relatively controllable, and thus has received extensive attention in both the academic and industrial fields.

[0003] Early transition metal catalysts, as a kind of polyolefin catalysts with low cost, high activity, and simple preparation process, are widely used in industrial production. However, due to the highly electrophilic and oxygenophilic nature of early transition metals themselves, in the copolymerization reaction of olefin polar monomers, the metal center is extremely vulnerable to being poisoned by polar functional groups and losing catalytic activity. Therefore, how to overcome this shortcoming has become a hot issue of concern to global scientific research personnel.

[0004] NHC (N-heterocyclic carbene) ligands have strong electron-donating abilities. In terms of the inductive effect, two nitrogen atoms with relatively high electronegativity are connected to the carbene carbon atom. Due to the electron-withdrawing effect of the nitrogen atoms, the lone pair electrons on the carbene carbon atom tend to be stable, which can increase the stability of the system. Therefore, N-heterocyclic carbene is a relatively stable system. Because N-heterocyclic carbene has relatively high stability and strong electron-donating ability, it can form stable compounds with most transition metals. Metal catalysts containing N-heterocyclic carbene are not easily decomposed during the catalytic reaction process, which plays an important role in improving the economy of the reaction.

[0005] In the application of bimetallic complex catalysts, when the bimetallic centers are in a suitable orientation and distance, they will affect the kinetics of processes such as monomer coordination, insertion, and chain transfer through synergy, showing special catalytic performance. When copolymerizing non-polar monomers such as ethylene and α-olefins, if the monomer size matches the distance between the bimetallic centers, the coordination and insertion of the comonomer can be assisted through the interaction between the metal and the monomer, thereby increasing the insertion ratio of the comonomer. When copolymerizing ethylene with polar monomers containing O, S, N, etc., the second metal center can capture the polar monomer through the interaction with the polar group, avoiding the simultaneous poisoning and inactivation of the two metal centers and promoting the coordination and insertion of the polar monomer. The application of the bimetallic effect can achieve polymerization effects that are difficult to achieve with a single metal center and plays an important role in the synthesis of new polyolefin materials. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the present invention provides a binuclear vanadium catalyst containing a bis-NHC ligand, a preparation method thereof, and uses thereof. The binuclear vanadium catalyst containing a bis-NHC ligand is used for catalyzing ethylene homopolymerization and copolymerization of ethylene and its polar monomers, and precisely regulates the steric hindrance and electronic effect of the catalyst by adjusting the ligand skeleton to prepare functionalized polyolefin materials.

[0007] To achieve the above object and other related objects, the present invention provides a binuclear vanadium catalyst containing a bis-NHC ligand, and its structural general formula is:

[0008]

[0009] Among them, the structural formula of Linker in the structural general formula is: or or ; R1, R2, R3, R4, R5 are each independently selected from any one of a hydrogen atom, an alkyl group, a fluorine atom, and a phenyl group, and R´1, R´2, R´3, R´4, R´5 correspond to R1, R2, R3, R4, R5 one by one.

[0010] The present invention also provides a preparation method of a binuclear vanadium catalyst containing a bis-NHC ligand, including the following steps:

[0011] (1) Under a nitrogen atmosphere, add a first reagent, a second reagent, and 2,4,6-trimethylphenylimidazole to a reaction tube, place the reaction tube in a first oil bath and stir for 12 h. After removing the solvent in the reaction tube by pumping with a vacuum pump, wash and recrystallize with methanol and ether, let it stand at a low temperature, and remove the solvent of the recrystallization under vacuum to obtain a white powder first product;

[0012] (2) Under a nitrogen atmosphere, weigh the third reagent into a reaction flask, add n-octane and vanadium oxychloride to the reaction flask, and place the reaction flask in a second oil bath for heating and stirring for 20 h; after the reaction is completed, filter through diatomaceous earth to obtain a dark green filtrate. The dark green filtrate is vacuum-evaporated to remove the solvent, washed with n-hexane and dichloromethane, and then recrystallized. It is left standing at -5 °C for 12 h, and the solvent of the recrystallization is removed under vacuum to obtain a dark green powder of the second product; during the reaction process, the carbon dioxide gas generated in the reaction flask is displaced on a double-tube. The displacement is carried out once every 20 min during the reaction time of 1-3 h, once every 1 h during 4-6 h, and once every 7 h during the reaction time of 6-20 h;

[0013] (3) Weigh the first product into a reaction flask, add toluene to dissolve it to obtain a solution of the first product. Slowly add the fourth reagent to the solution of the first product, then place the reaction flask in a glove box and stir at room temperature for 3 h. After adding the second product, continue to stir at room temperature for 0.5 h. Filter the reaction solution through diatomaceous earth, vacuum-evaporate to remove the solvent, and precipitate with cold n-hexane to obtain the brown powder of the dinuclear vanadium catalyst containing a bis-NHC ligand; the second product includes any one of 2,6-dimethylphenylvanadium trichloride, 2,4-difluorophenylvanadium trichloride, and 2-biphenylvanadium trichloride.

[0014] In an example of the present invention, the molar ratio of the first reagent to 2,4,6-trimethylphenylimidazole is 1:2; the first reagent is selected from any one of 1,6-dibromohexane, 1,8-dibromooctane, and 1,4-bis(bromomethyl)benzene; the second reagent is selected from toluene or dichloromethane. When the second reagent is toluene, the temperature of the first oil bath is 110 °C; when the second reagent is dichloromethane, the temperature of the first oil bath is 45 °C.

[0015] In an example of the present invention, the second reagent is toluene or dichloromethane, the third reagent is selected from any one of 2,6-dimethylphenyl isocyanate, 2,4-difluorophenyl isocyanate, and 2-biphenyl isocyanate, and the temperature of the second oil bath is 120-140 °C.

[0016] In an example of the present invention, the fourth reagent is selected as potassium tert-butoxide, and the molar ratio of the first product to the fourth reagent and the second product is 1:2:2.

[0017] The present invention also provides a use of a dinuclear vanadium catalyst containing a bis-NHC ligand, and the dinuclear vanadium catalyst is applied to catalyze olefin coordination polymerization.

[0018] In an example of the present invention, the dinuclear vanadium catalyst containing a bis-NHC ligand is applied to catalyze the coordination copolymerization of olefins and polar olefin monomers containing polar functional groups to prepare functionalized polyolefin materials.

[0019] In one example of the present invention, the process of applying the binuclear vanadium catalyst containing a bis-NHC ligand to catalyze the coordination copolymerization of an olefin and a polar olefin monomer containing a polar functional group is as follows: Under the protection of an anhydrous and oxygen-free nitrogen atmosphere, the inside of the high-pressure reactor is brought to the reaction temperature. A magnetic stir bar, a cocatalyst dissolved in a fifth reagent, a polar monomer, and a binuclear vanadium catalyst containing a bis-NHC ligand dissolved in a fifth reagent are successively added to the high-pressure reactor. Ethylene gas is introduced into the high-pressure reactor and the reaction is carried out for 5 minutes. The reaction solution is poured into a mixed solution of ethanol and hydrochloric acid for precipitation, and then dried in vacuo until the mass remains unchanged to obtain a coordination polymerization product.

[0020] In one example of the present invention, the polar monomer is selected from any one of 6-chloro-1-hexene, methyl acrylate, 10-undecenoic acid, 10-undecenol, and methyl 10-undecenoate. The cocatalyst is selected as diethylaluminum chloride. The molar ratio of the binuclear vanadium catalyst containing a bis-NHC ligand to the polar monomer is 1:1000 - 15000.

[0021] In one example of the present invention, the fifth reagent includes any one of toluene, benzene, and chlorobenzene; the reaction temperature is 0 - 75 °C.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The catalyst synthesis steps in the present invention are simple, easy to operate, the experimental conditions are mild and not harsh, the reaction is easy to carry out, and the yield is high.

[0024] (2) For the coordination polymerization carried out in the present invention, the raw materials are inexpensive, widely available, and easy to obtain, and the synthesis cost is low, which has industrial application value.

[0025] (3) In the present invention, the binuclear vanadium catalyst containing a bis-NHC ligand is first used for the copolymerization of ethylene and a polar monomer. By introducing an NHC ligand with strong electron-donating ability, a stable compound is formed with the transition metal to avoid the decomposition of the catalyst during the catalytic process. And by utilizing the synergistic effect between the binuclear metal centers, the poisoning and inactivation of the metal center by the polar monomer are avoided, and the coordination insertion of the polar monomer is promoted. It promotes the further development of vanadium catalysts in the field of copolymerization of ethylene and polar monomers, and has strong original innovation.

[0026] (4) The dinuclear vanadium catalyst system containing bis-NHC ligands prepared in the present invention can enable the copolymerization of ethylene with various polar monomers very well, and olefin polymers with different properties and functions can be obtained. At the same time, the introduction of NHC ligands makes the catalyst structure more stable, and the catalyst can still have catalytic activity at a relatively high reaction temperature, making up for the defect that the previous early transition metal catalyst system is decomposed at high temperature and loses the ability to catalyze olefin polymerization. The dinuclear vanadium catalyst system containing bis-NHC ligands further broadens the types of polar monomers and the reaction temperature in copolymerization, providing a brand-new idea for the preparation of different functional polyolefins. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 1H NMR spectrum of the first product in Example 1 of the present invention;

[0029] Figure 2 1H NMR spectrum of the second product in Example 1 of the present invention;

[0030] Figure 3 1H NMR spectrum of Cat.1 in Example 1 of the present invention;

[0031] Figure 4 1H NMR spectrum of the first product in Example 2 of the present invention

[0032] Figure 5 1H NMR spectrum of Cat.2 in Example 2 of the present invention;

[0033] Figure 6 1H NMR spectrum at high temperature of the polymer obtained by the successful copolymerization of 10-undecenol and ethylene in Example 3 of the present invention;

[0034] Figure 7 1H NMR spectrum at high temperature of the polymer obtained by the successful copolymerization of 6-chloro-1-hexene and ethylene in Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. It should also be understood that the terms used in the embodiments of the present invention are for describing specific embodiments and are not intended to limit the protection scope of the present invention. The test methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by each manufacturer.

[0036] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of clear narration and are not intended to limit the scope of implementation of the present invention. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope of implementation of the present invention.

[0037] The present invention provides a dinuclear vanadium catalyst containing a bis-NHC ligand, and its structural general formula is:

[0038]

[0039] Among them, the structural formula of Linker in the structural general formula is: or or ; R1, R2, R3, R4, R5 are each independently selected from any one of a hydrogen atom, an alkyl group, a fluorine atom, and a phenyl group, and R´1, R´2, R´3, R´4, R´5 correspond to R1, R2, R3, R4, R5 one by one. For example, if R1 is a hydrogen atom, R´1 is also a hydrogen atom; if R2 is an alkyl group, R´2 is also an alkyl group; if R3 is a fluorine atom, R´3 is also a fluorine atom. This is not listed one by one here.

[0040] The present invention also provides a preparation method of a dinuclear vanadium catalyst containing a bis-NHC ligand, which includes the following steps:

[0041] (1) Under a nitrogen atmosphere, a first reagent, a second reagent, and 2,4,6-trimethylphenylimidazole are sequentially added to a reaction tube. The reaction tube is placed in a first oil bath and stirred for 12 h. After removing the solvent in the reaction tube by vacuum pumping with an oil pump, it is washed and recrystallized with methanol and ether, left to stand at low temperature, and the solvent is removed under vacuum to obtain a white powder as the first product;

[0042] (2) Under a nitrogen atmosphere, weigh the third reagent into a reaction flask, add the solvent n-octane and vanadyl trichloride to the reaction flask, and place the reaction flask in a second oil bath for heating and stirring for 20 h; after the reaction is completed, filter through diatomaceous earth to obtain a dark green filtrate. The dark green filtrate is evaporated to remove the solvent under vacuum, washed with n-hexane and dichloromethane, and then recrystallized. It is left standing at -5 °C for 12 h, and the solvent for recrystallization is removed under vacuum to obtain a dark green powder of the second product; during the reaction process, the carbon dioxide gas generated in the reaction flask is displaced on a double-tube. The displacement is carried out once every 20 min during the reaction time of 1 - 3 h, once every 1 h during the reaction time of 4 - 6 h, and once every 7 h during the reaction time of 6 - 20 h;

[0043] (3) Weigh the first product into a reaction flask, dissolve it with toluene to obtain a solution of the first product. Slowly add the fourth reagent to the solution of the first product, then place the reaction flask in a glove box and stir at room temperature for 3 h. After adding the second product, continue to stir at room temperature for 0.5 h. Filter the reaction solution through diatomaceous earth, evaporate to remove the solvent under vacuum, and precipitate with cold n-hexane to obtain the brown powder of the binuclear vanadium catalyst containing the double NHC ligand; among them, the second product includes any one of 2,6-dimethylphenylvanadium trichloride, 2,4-difluorophenylvanadium trichloride, and 2-biphenylvanadium trichloride.

[0044] In step (1), the first reagent is selected from any one of 1,6-dibromohexane, 1,8-dibromooctane, and 1,4-bis(bromomethyl)benzene, and the molar ratio of the first reagent to 2,4,6-trimethylphenylimidazole is 1:2; the second reagent is selected from toluene or dichloromethane. If the second reagent is toluene, the temperature of the first oil bath is 110 °C; if the second reagent is dichloromethane, the temperature of the first oil bath is 45 °C.

[0045] In step (2), the third reagent is selected from any one of 2,6-dimethylphenyl isocyanate, 2,4-difluorophenyl isocyanate, and 2-biphenyl isocyanate; the temperature of the second oil bath is 120 - 140 °C. For example, the temperature of the second oil bath can be any temperature within the above temperature range, such as 120 °C, 130 °C, or 140 °C.

[0046] In step (3), potassium tert-butoxide is selected as the fourth reagent, and the molar ratio of the first product, the fourth reagent, and the second product is 1:2:2. The second product can be 2,6-dimethylphenylvanadium trichloride, can be 2,4-difluorophenylvanadium trichloride, or can be 2-biphenylvanadium trichloride. Specifically, the second product is determined by the third reagent added in step (2). When the third reagent in step (2) is 2,6-dimethylphenyl isocyanate, the second product is 2,6-dimethylphenylvanadium trichloride; when the third reagent in step (2) is 2,4-difluorophenyl isocyanate, the second product is 2,4-difluorophenylvanadium trichloride; when the third reagent in step (2) is 2-biphenyl isocyanate, the second product is 2-biphenylvanadium trichloride.

[0047] The general synthesis formula of the above catalyst is:

[0048]

[0049] Among them, R1, R2, R3, R4, and R5 each independently selected from any one of a hydrogen atom, an alkyl group, a fluorine atom, and a phenyl group, and R´1, R´2, R´3, R´4, and R´5 correspond to R1, R2, R3, R4, and R5 one by one.

[0050] The present invention also provides a use of a dinuclear vanadium catalyst containing a bis-NHC ligand. The dinuclear vanadium catalyst containing a bis-NHC ligand is applied to the catalytic coordination polymerization of olefins. Specifically, it is applied to the catalytic coordination copolymerization of olefins and polar olefin monomers containing polar functional groups to prepare functionalized polyolefin materials.

[0051] Among them, the process of applying the dinuclear vanadium catalyst containing a bis-NHC ligand to the catalytic coordination copolymerization of olefins and polar olefin monomers containing polar functional groups is as follows: Under the protection of an anhydrous and oxygen-free nitrogen atmosphere, the inside of the high-pressure reaction kettle is at the reaction temperature. A magnetic stirrer, a cocatalyst dissolved in a fifth reagent, and a polar monomer are sequentially added to the high-pressure reaction kettle. Finally, a dinuclear vanadium catalyst containing a bis-NHC ligand dissolved in a fifth reagent is added. Ethylene gas is introduced into the high-pressure reaction kettle and stirred for 5 minutes. The reaction solution is poured into a mixed solution of ethanol and hydrochloric acid and dried under vacuum until the mass remains unchanged to obtain a coordination polymerization product.

[0052] The polar monomer is selected from any one of 6-chloro-1-hexene, methyl acrylate, 10-undecenoic acid, 10-undecenol, and methyl 10-undecenoate. The cocatalyst is selected as diethylaluminum chloride. The molar ratio of the binuclear vanadium catalyst containing a bis-NHC ligand to the polar monomer is 1:1000 - 15000. For example, the molar ratio of the catalyst to the polar monomer can be any value within the above range, such as 1:1000, 1:5000, 1:10000, or 1:15000. The fifth reagent is selected from any one of toluene, benzene, and chlorobenzene; the reaction temperature is 0 - 75 °C. For example, the reaction temperature can be any value within the above temperature range, such as 0 °C, 20 °C, 50 °C, or 75 °C.

[0053] The general formula for the above olefin coordination polymerization is as follows:

[0054]

[0055] V cat. =

[0056]

[0057] Wherein, R1, R2, R3, R4, and R5 are each independently selected from any one of a hydrogen atom, an alkyl group, a fluorine atom, and a phenyl group, and R´1, R´2, R´3, R´4, and R´5 respectively correspond to R1, R2, R3, R4, and R5 one by one. For example, when R1 is a hydrogen atom, R´1 is also a hydrogen atom; when R2 is an alkyl group, R´2 is also an alkyl group; when R3 is a fluorine atom, R´3 is also a fluorine atom. This is not listed one by one here.

[0058] The technical solutions of the present invention will be described in detail through several specific examples below. Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the examples can be commercially purchased.

[0059] Example 1

[0060] (1)Preparation of octane-linked bis 1-(2,4,6-trimethylphenyl)-imidazole bromide: Under nitrogen protection, weigh 1,8-dibromooctane (182.25 mg, 0.67 mmol) into a 15 mL thick-walled pressure-resistant tube, and then successively add toluene (5 mL) and 2,4,6-trimethylphenylimidazole (250 mg, 1.34 mmol). Place the thick-walled pressure-resistant tube in an oil bath at 110 °C and stir for 12 h. Solids precipitate from the white reaction solution. After removing the solvent under vacuum, dissolve the solids in a small amount of dichloromethane just until dissolved. Drop it into ether, and white powder precipitates. After ultrasonic homogenization, let it stand. Repeat washing with dichloromethane and ether, let it stand in the refrigerator, and remove the solvent under vacuum to obtain 227 mg of white powder of octane-linked bis 1-(2,4,6-trimethylphenyl)-imidazole bromide, with a yield of 52.5%;

[0061] (2)Preparation of 2,6-dimethylvanadium trichloride: Under the protection of a nitrogen atmosphere in a glove box, weigh 2,6-dimethylphenyl isocyanate (555 mg, 3.77 mmol) into a Schlenk flask, and then successively add n-octane (15 ml) and vanadium oxychloride (981 mg, 5.66 mmol). Place the Schlenk flask in an oil bath at 130 °C and heat and stir for 20 h. During the reaction, displace the carbon dioxide gas generated in the reaction flask on a double-tube. Replace it every 20 min within 1 - 3 h of the reaction time, every 1 h within 4 - 6 h of the reaction time, and every 7 h within 6 - 20 h of the reaction time. At the end of the reaction, a dark green reaction solution is obtained. Open the Schlenk flask in the glove box. Filter the reaction solution through diatomaceous earth to obtain a dark green filtrate. Rinse the diatomaceous earth with dichloromethane and collect the filtrate in a 100 ml single-neck flask. Then remove the solvent under vacuum with a vacuum pump in the glove box to obtain a dark green solid. Add dichloromethane just until dissolved, and drop it into n-hexane for recrystallization. Let it stand at -5 °C for 12 h. Recrystallize three times repeatedly. Remove the upper layer solution, collect the lower layer precipitate, and vacuum dry the precipitate to obtain 476.2 mg of dark green powder of 2,6-dimethylphenylvanadium trichloride, with a yield of 31%. The structural formula of 2,6-dimethylphenylvanadium trichloride is as follows:

[0062]

[0063] (3) Weigh octane-linked bis 1-(2,4,6-trimethylphenyl)-imidazolium bromide (116.66 mg, 0.181 mmol) and put it into a screw-cap bottle. Add toluene (5 ml), and then slowly add potassium tert-butoxide (40.6 mg, 0.362 mmol). After stirring at room temperature for 3 h, a turbid yellow reaction solution is obtained. Then add vanadium(III) chloride 2,6-dimethylphenyl (100.00 mg, 0.362 mmol) and continue stirring at room temperature for 0.5 h. Filter the reaction solution through diatomaceous earth and concentrate it under vacuum. Drop it into cold hexane to precipitate a brownish powder, and obtain the main catalyst Cat.1. The structure of the main catalyst Cat.1 is as follows:

[0064]

[0065] Figures 1 to 3 They are the 1H NMR spectra of octane-linked bis 1-(2,4,6-trimethylphenyl)-imidazolium bromide, vanadium(III) chloride 2,6-dimethylphenyl and the main catalyst Cat.1 respectively. It can be seen from Figures 1 to 3 that the product structure is correct.

[0066] Example 2

[0067] (1) Preparation of cyclo-bis(methylene)-bis 1-(2,4,6-trimethylphenyl)-imidazole: Under nitrogen protection, weigh 1,4-bis(bromomethyl)benzene (176.85 mg, 0.67 mmol) into a 15 mL thick-walled pressure-resistant tube. Add dichloromethane (5 mL) and 2,4,6-trimethylphenylimidazole (250 mg, 1.34 mmol) in sequence. Place the thick-walled pressure-resistant tube in an oil bath and stir at 45 °C for 12 h. The tube contains a yellow turbid liquid. Remove the solvent under vacuum to obtain a light yellow solid. Dissolve the solid exactly in methanol to obtain a light yellow liquid, and drop it into ether to precipitate a white powder. After ultrasonic homogenization, let it stand. Repeat washing with methanol and ether, let it stand in the refrigerator, and remove the solvent under vacuum to obtain 337 mg of white powder of cyclo-bis(methylene)-bis 1-(2,4,6-trimethylphenyl)-imidazole, with a yield of 79%.

[0068] (2) The preparation method of vanadium(III) chloride 2,6-dimethylphenyl refers to Example 1.

[0069] (3) Weigh cyclodimethylene bis-1-(2,4,6-trimethylphenyl)-imidazole (100 mg, 0.155 mmol) into a screw-cap bottle, add toluene (5 ml), and then slowly add potassium tert-butoxide (35 mg, 0.31 mmol). After stirring at room temperature for 3 hours, a turbid yellow reaction solution is obtained. Then, 2,6-dimethylvanadium trichloride (85.7 mg, 0.31 mmol) is added and continued to stir at room temperature for 0.5 hours. The reaction solution is filtered through diatomaceous earth and concentrated in vacuo. It is then added dropwise to cold hexane for precipitation to obtain a brown powder main catalyst Cat.2. The structure of the main catalyst Cat.2 is as follows:

[0070]

[0071] Figure 4 and Figure 5 The NMR hydrogen spectra of cyclodimethylene-linked 1-(2,4,6-trimethylphenyl)-imidazole and the main catalyst Cat.2 prepared in this example are respectively Figure 4 and Figure 5 It can be seen that the structure of the prepared product is correct.

[0072] Example 3

[0073] Copolymerization of ethylene and 10-undecenol: In a glove box, weigh 0.5 μmol of the main catalyst Cat.1 prepared in Example 1 in a 10 ml Shrek bottle, and add 2 g of toluene; weigh 250 μmol of the co-catalyst diethylaluminum chloride in another 10 ml Shrek bottle, and add 3.5 g of toluene; weigh 10-undecenol (850 mg, 5.0 mmol) in a 50 ml Shrek bottle, and add 2 g of toluene to ensure that the total volume of the reaction is about 10 ml. Take the three Shrek bottles out of the glove box, connect the double-row tubes, replace the oxygen in the rubber pipeline, replace it three times, and finally put the double-row tubes in a nitrogen-filled state, and use a syringe to inject 10-undecenol, co-catalyst diethylaluminum chloride, and main catalyst Cat.1 into the reactor in sequence. The reactor is dried in a high-temperature drying oven in advance and evacuated. The reactor is soaked in an ice-water mixture to maintain the reactor at 0 ° C.

[0074] Ethylene gas at a pressure of 4 atm was introduced into the kettle, the valve above the kettle was opened, the nitrogen in the kettle was removed, and the magnetic stirring was turned on to start the reaction. The reaction time was 5 minutes. After the reaction was completed, the ethylene gas valve was closed, and the pressure was released and the kettle was disassembled. The reaction liquid was poured into a mixed solution of 50 ml of ethanol and 15 ml of hydrochloric acid, stirred for 12 hours, and the white solid was collected and dried in a high-temperature vacuum drying oven at 50°C for 6 hours until the polymer had a constant weight.

[0075] Figure 6 This is a high temperature H-NMR spectrum of the polymer prepared in this example, indicating that 10-undecenol and ethylene are successfully copolymerized.

[0076] Example 4

[0077] Copolymerization of ethylene and 6-chloro-1-hexene: In a glove box, weigh 0.5 μmol of the main catalyst Cat.1 prepared in Example 1 into a 10-ml Schlenk flask, and add 2 g of toluene; weigh 250 μmol of the cocatalyst diethylaluminum chloride into another 10-ml Schlenk flask, and add 3.5 g of toluene; weigh 6-chloro-1-hexene (593 mg, 5 mmol) into a 50-ml Schlenk flask, and add 2 g of toluene to ensure that the total volume of the reaction is 10 ml. Take the three Schlenk flasks out of the glove box, connect the double-tube, displace the oxygen in the rubber pipeline three times, and finally the double-tube is in a nitrogen-passing state. Inject 6-chloro-1-hexene, the cocatalyst diethylaluminum chloride, and the main catalyst Cat.1 into the reaction kettle in sequence with a syringe. The reaction kettle is dried in a high-temperature drying oven in advance and evacuated. The reaction kettle is immersed in an ice-water mixture to keep the kettle body at 0 °C.

[0078] Introduce ethylene gas with a pressure of 4 atm into the kettle. Open the valve above the kettle body, exhaust the nitrogen in the kettle body, and then turn on the magnetic stirrer to start the reaction. The reaction time is 5 min. After the reaction is completed, close the ethylene gas valve, relieve the pressure, and disassemble the kettle. Pour the reaction solution into a mixed solution of 50 ml of ethanol and 15 ml of hydrochloric acid, stir for 12 h, collect the white solid, and vacuum-dry it at 50 °C in a high-temperature vacuum drying oven for 6 h until the polymer reaches a constant weight.

[0079] Figure 7 The high-temperature 1H NMR spectrum of the polymer prepared in this example shows that 6-chloro-1-hexene and ethylene have successfully copolymerized.

[0080] The above embodiments merely illustrate the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A binuclear vanadium catalyst containing a bis-NHC ligand, characterized in that, Its structural general formula is: Among them, the structural formula of Linker in the general structural formula is: or ; R1, R2, R3, R4, and R5 are each independently selected from any one of a hydrogen atom and an alkyl group, and R´1, R´2, R´3, R´4, and R´5 correspond to R1, R2, R3, R4, and R5 one by one.

2. A method for preparing a dinuclear vanadium catalyst containing a double NHC ligand according to claim 1, characterized in that, It includes the following steps: (1) Under a nitrogen atmosphere, add the first reagent, the second reagent, and 2,4,6-trimethylphenylimidazole into a reaction tube. Place the reaction tube in a first oil bath and stir for 12 h. After removing the solvent in the reaction tube by pumping with a vacuum pump, wash and recrystallize with methanol and ether, let it stand at a low temperature, and remove the solvent of the recrystallization under vacuum to obtain a white powder of the first product; (2) Under a nitrogen atmosphere, weigh the third reagent into a reaction flask, add n-octane and vanadium oxychloride to the reaction flask, and place the reaction flask in a second oil bath and heat and stir for 20 h; after the reaction is completed, filter through diatomaceous earth to obtain a dark green filtrate. The dark green filtrate is vacuum-evaporated to remove the solvent, washed with n-hexane and dichloromethane and then recrystallized, left to stand at -5 °C for 12 h, and the solvent of the recrystallization is removed under vacuum to obtain a dark green powder of the second product; during the reaction process, replace the carbon dioxide gas generated in the reaction flask on a double-tube, replace it once every 20 min for 1 - 3 h of reaction time, replace it once every 1 h for 4 - 6 h of reaction time, and replace it once every 7 h for 6 - 20 h of reaction time; (3) Weigh the first product into a reaction flask, dissolve it with toluene to obtain a solution of the first product. Slowly add the fourth reagent to the solution of the first product, then place the reaction flask in a glove box and stir at room temperature for 3 h. After adding the second product, continue to stir at room temperature for 0.5 h. After filtering the reaction solution through diatomaceous earth, remove the solvent under vacuum, precipitate with cold hexane to obtain a brown powder of the dinuclear vanadium catalyst containing a bis-NHC ligand; wherein, the second product includes any one of 2,6-dimethylphenylvanadium trichloride, 2,4-difluorophenylvanadium trichloride, and 2-biphenylvanadium trichloride.

3. The preparation method of the dinuclear vanadium catalyst containing a double NHC ligand according to claim 2, characterized in that, The molar ratio of the first reagent to the 2,4,6-trimethylphenylimidazole is 1:2; the first reagent is selected from any one of 1,6-dibromohexane, 1,8-dibromooctane, and 1,4-bis(bromomethyl)benzene; the second reagent is selected from toluene or dichloromethane. When the second reagent is toluene, the temperature of the first oil bath is 110 °C; when the second reagent is dichloromethane, the temperature of the first oil bath is 45 °C.

4. The preparation method of the dinuclear vanadium catalyst containing a double NHC ligand according to claim 2, characterized in that, The third reagent is selected from any one of 2,6-dimethylphenyl isocyanate, 2,4-difluorophenyl isocyanate, and 2-biphenyl isocyanate, and the temperature of the second oil bath is 120 - 140 °C.

5. The preparation method of the dinuclear vanadium catalyst containing a double NHC ligand according to claim 2, wherein, The fourth reagent is selected as potassium tert-butoxide, and the molar ratio of the first product to the fourth reagent and the second product is 1:2:

2.

6. Use of the dinuclear vanadium catalyst containing a bis-NHC ligand according to claim 1, characterized in that, The dinuclear vanadium catalyst containing a bis-NHC ligand is used in the catalytic coordination polymerization of olefins.

7. Use of the dinuclear vanadium catalyst containing a double NHC ligand according to claim 6, characterized in that, The dinuclear vanadium catalyst containing a bis-NHC ligand is used in the catalytic coordination copolymerization of olefins and polar olefin monomers containing polar functional groups to prepare functional polyolefin materials.

8. Use of the dinuclear vanadium catalyst containing a double NHC ligand according to claim 6, characterized in that, The process of applying the dinuclear vanadium catalyst containing a bis-NHC ligand to the coordination copolymerization of an olefin and a polar olefin monomer containing a polar functional group is as follows: Under the protection of an anhydrous and oxygen-free nitrogen atmosphere, the inside of the high-pressure reactor is brought to the reaction temperature. A magnetic stir bar, a cocatalyst dissolved in a fifth reagent, a polar monomer, and a dinuclear vanadium catalyst containing a bis-NHC ligand dissolved in a fifth reagent are successively added to the high-pressure reactor. Ethylene gas is introduced into the high-pressure reactor and reacted for 5 min. The reaction solution is poured into a mixed solution of ethanol and hydrochloric acid for precipitation, and vacuum dried until the mass remains unchanged to obtain a coordination polymerization product.

9. Use of the dinuclear vanadium catalyst containing a double NHC ligand according to claim 8, characterized in that: The polar monomer is selected from any one of 6-chloro-1-hexene, methyl acrylate, 10-undecenoic acid, 10-undecenol, and methyl 10-undecenoate. The cocatalyst is selected as diethylaluminum chloride. The molar ratio of the dinuclear vanadium catalyst containing a bis-NHC ligand to the polar monomer is 1:1000 to 15000.

10. Use of the binuclear vanadium catalyst containing a double NHC ligand according to claim 8, characterized in that: The fifth reagent is selected from any one of toluene, benzene, and chlorobenzene. The reaction temperature is 0 to 75 °C.

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