Preparation method of bridged metallocene compound capable of improving utilization rate of ligand

Abstract

The invention provides a preparation method of a bridged metallocene compound capable of improving the utilization rate of a ligand. According to the method, the utilization rate of the bridged double-metallocene ligand is increased through the ether complex, so that the total yield of the bridged metallocene catalyst with two configurations of rac and meso is high.

Description

Technical Field

[0001] This invention belongs to the field of metallocene catalysts, and specifically relates to a method for preparing bridging metallocene compounds that can improve ligand utilization. Background Technology

[0002] Metallocene catalyst systems, composed of transition metal (such as titanium, zirconium, and hafnium) metallocene compounds and co-catalysts (such as methylaluminoxane), are homogeneous catalysts with a single catalytic active site. Compared to traditional Ziegler catalysts... Nano-Zn (ZN) catalyst systems, a type of metallocene catalyst system, exhibit polymer products with narrower molecular weight distributions and better comonomer insertion rates. Furthermore, polymer properties can be altered by changing the conformational changes of ligands within the catalyst. These catalysts have been widely used in the catalytic polymerization of ethylene, propylene, or the polymerization of ethylene with α-polymers. Olefin copolymerization has greatly enriched the variety of high-performance polyolefins. Since the 1980s, the variety of metallocene catalysts has become increasingly diverse, ranging from monometallocene to dimetallocene, from unbridged to bridged structures, and from C-bridges to Si-bridges. Among them, bridged dimetallocene catalysts are characterized by high activity and good structural stability, and their spatial conformation is conducive to the formation of highly isotactic polyolefin products. These bridged dimetallocene catalysts have been applied to the commercial production of polypropylene, polyethylene, or polyolefin copolymers.

[0003] The preparation of bridged bis-lithocene compounds generally involves first reacting the bridged bis-lithocene compound with alkyllithium for bis-lithiation, followed by reaction with metallocene compounds such as zirconium chloride.

[0004] Bridged bis-metallocene catalysts possess chiral structures and exhibit a mixture of two spatial isomers: a racemic structure (rac-structure) and a meso structure (meso-structure). Of these two isomers, the rac-structure is more valuable in the polyolefin field due to its high olefin polymerization activity, strong copolymerization ability, and highly isotactic polymerization products. The meso-structure... Due to its poor olefin polymerization performance, the structure is rarely used in the field of olefin polymerization.

[0005] Methods for converting meso-structures into rac-structures have been developed. Therefore, increasing the overall yield of the rac+meso structure can lead to a high yield of the rac product. However, the utilization rate of metallocene ligands is currently low, resulting in a low overall yield of the rac+meso structure. Therefore, there is an urgent need to develop a method to improve the overall yield. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing bridged metallocene compounds, comprising the following steps:

[0007] In the above equations (1)-(2): M is selected from titanium, zirconium, or hafnium; Q represents a silicon bridge or a carbon bridge; The two X's are the same or different, and are independently selected from halogens and carbon. 1~10 Alkyl and C 2~10 One or two of the alkenyl groups; R1, R2, R3, and R4 may be the same or different, and are independently selected from hydrogen, C, and C, respectively. 1~20 Alkyl, C 3~6 cycloalkyl and C 6~14 One or more of the aryl groups; R5 and R6 may be the same or different, and are independently selected from C. 1~10 Alkyl and C 6~14 One or two of the aryl groups; Step 1: Under an inert atmosphere, the compound of formula (1) is dissolved in an ether-containing solvent and reacted with alkyl lithium to obtain an ether complex of a bridged dilithium bis(lithium) salt. Step 2: Under an inert atmosphere, the ether complex of the bridged bis(lithium)-ceramic salt, MX4(THF)2 and ether are mixed and reacted under controlled temperature. After post-treatment, the bridged bis(lithium)-ceramic compound shown in formula (2) is obtained.

[0008] According to an embodiment of the present invention, each X is independently selected from F, Cl, Br, I, C. 1~6 Alkyl (e.g., C) 1~4 alkyl) or C 2~6 Alkenyl, for example, Cl, methyl, ethyl, propyl or butyl.

[0009] According to an embodiment of the present invention, R1, R2, R3, and R4 are each independently selected from hydrogen, C, and C. 1~10 Alkyl (e.g., C) 1~6 Alkyl, C 1~4 Alkyl), C 3~6 cycloalkyl or C 6~14 Aryl groups, for example, selected from hydrogen, methyl, ethyl, propyl, butyl, cyclopropyl, and phenyl.

[0010] According to an embodiment of the present invention, R5 and R6 are each independently selected from C. 1~6 Alkyl (e.g., C) 1~4 alkyl) or C 6~10 Aryl groups, such as methyl, ethyl, propyl, butyl, or phenyl.

[0011] According to an embodiment of the present invention, the compound of formula (1) is dimethylbis(2-methyl-4-phenylinden-1-yl)silane.

[0012] According to an embodiment of the present invention, the ethers in steps 1 and 2 may be the same or different, and are independently selected from C. 1~10 Alkyl ethers, such as C 1~4 Alkyl ethers, exemplified by one or more of diethyl ether, propyl ether, and butyl ether.

[0013] According to an embodiment of the present invention, the ether-containing solvent is a mixture of ether and organic solvent (e.g., n-hexane or toluene); preferably, the volume percentage of ether in the ether-containing solvent is greater than 1 / 3, for example, not less than 1 / 2.

[0014] According to an embodiment of the present invention, the alkyllithium is selected from C 1~6 Alkyl lithium, such as C 1~4 Alkyl lithium, exemplified by methyl lithium, tert-butyl lithium, or n-butyl lithium.

[0015] According to an embodiment of the present invention, the alkyllithium is added dropwise to the system at a low temperature (e.g., -20ºC to 20ºC) and reacted for 0.2 to 1 h (e.g., 0.5 h), and then the reaction is brought up to room temperature for 8 to 15 h (e.g., 12 h).

[0016] According to an embodiment of the present invention, step 1 includes: dissolving the compound of formula (1) in an ether-containing solvent under a nitrogen atmosphere, adding n-butyllithium dropwise at a low temperature (e.g., -20ºC to 20ºC), reacting for 0.2 to 1 h (e.g., 0.5 h) after the addition is complete, then raising the temperature to room temperature and reacting for 8 to 15 h (e.g., 12 h), removing the solvent under vacuum, adding hexane and stirring, filtering, washing, and drying to obtain the ether complex of the bridged dilithium bis(petroleum) salt.

[0017] According to an embodiment of the present invention, the ether in step 2 is an anhydrous ether, such as one or more of anhydrous diethyl ether, anhydrous propyl ether and anhydrous butyl ether.

[0018] According to an embodiment of the present invention, in step 2, the ether complex of the bridged dilithium cyclohexene salt and the ether are first mixed at low temperature (-40ºC~10ºC) to form a solution (the solution concentration is 0.01~0.2mol / L), and then MX4(THF)2 is added to the solution.

[0019] According to an embodiment of the present invention, the temperature-controlled reaction in step 2 includes: first reacting at a low temperature (-40ºC~10ºC) for 1~3 hours, then heating to room temperature for 1~3 hours, and then heating to 40~80ºC (e.g. 40~50ºC, 50~60ºC) for 6~20 hours (e.g. 12~18 hours).

[0020] According to an embodiment of the present invention, the post-processing in step 2 includes: after the reaction is completed, the solvent is dried under reduced pressure, toluene is added and heated to 50~70ºC, stirred, and hot filtered; the filtrate is concentrated by heating, n-hexane is added, crystals are precipitated at low temperature (-5~5ºC), filtered, and the solid is dried to obtain the bridged biscenocene compound shown in formula (2).

[0021] According to an embodiment of the present invention, the inert atmosphere is provided by nitrogen, argon, etc.

[0022] Beneficial effects The inventors discovered that by improving the utilization rate of bridged biscene ligands through ether complexes, and combined with a temperature-controlled process, the overall yield of both RAC and Meso-configured bridged metallocene catalysts was increased.

[0023] Terminology Definitions and Explanations Unless otherwise stated, the definitions of terms recorded in this application specification and claims, including definitions as examples, exemplary definitions, preferred definitions, and definitions of specific compounds in the embodiments, can be arbitrarily combined and combined with each other. Such combinations and combinations shall fall within the scope of this application specification.

[0024] Unless otherwise stated, the numerical ranges described in this specification and claims are equivalent to describing at least each specific integer value therein. For example, the numerical range "1-10" is equivalent to describing each integer value in the numerical range "1-10", namely 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0025] Term "C" 1-10 "alkyl" should be understood to refer to straight-chain and branched alkyl groups having 1 to 10 carbon atoms, "C 1-6 "Alkyl" means a straight-chain or branched alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, or 1,2-dimethylbutyl, or their isomers.

[0026] The term "alkoxy" refers to -O- (alkyl), where alkyl is defined as described above. Non-limiting examples of alkoxy groups include: methoxy, ethoxy, propoxy, and butoxy.

[0027] Term "C" 2~10"Alkenyl" should be understood as referring to straight-chain and branched alkenyl groups with 2 to 10 carbon atoms. 2~6 "Alkenyl" refers to a straight-chain or branched alkenyl group having 2, 3, 4, 5, or 6 carbon atoms. Examples of alkenyl groups include vinyl, propenyl, 1-butenyl, 2-butenyl, isobutenyl, 1-pentenyl, 2-pentenyl, 3-methyl-1-butenyl, etc.

[0028] Term "C" 3~6 "Cycloalkyl" should be understood to refer to straight-chain and branched cycloalkyl groups having 3 to 6 carbon atoms, such as cyclopropyl, cyclobutyl, methylcyclopropyl, cyclopentyl, cyclohexyl, or methylcyclopentyl.

[0029] Term "C" 6-14 "Aryl" should be understood as representing an aryl group having 6 to 14 carbon atoms. 6-12 "Aryl" refers to an aryl group having 6, 10, 12, or 14 carbon atoms. Examples of such aryl groups include phenyl, naphthyl, anthraceneyl, phenanthryl, pyrene, pentabenzophenanthryl, diphenylpyrene, or their isomers.

[0030] "Room temperature" refers to a temperature of 15~30ºC, preferably 25ºC. Attached Figure Description

[0031] Figure 1 The spectrum of crude dimethylsilyl bis(2-methyl-4-phenyl-indene)zirconium dichloride (rac+meso) from Example 1 is shown. Detailed Implementation

[0032] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0033] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0034] Example 1 Step 1. Preparation of the diethyl ether complex of dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt Under a nitrogen atmosphere, dimethylbis(2-methyl-4-phenylindenyl)silane (10 mmol, 1 eq., 4.7 g) was dissolved in toluene and diethyl ether (80 mL + 80 mL). A hexane reagent of n-butyllithium (22 mmol, 2.2 eq.) was added dropwise at -20°C for 0.5 h. The reaction was then allowed to proceed to room temperature for 12 h. The solvent was removed under vacuum, hexane was added and stirred, and the mixture was filtered, washed, and dried to obtain a yellow solid, which is the diethyl ether complex of dimethylsilylbis(2-methyl-4-phenyl-indenyl)dilithium salt.

[0035] Step 2. Preparation of bridged metallocene compounds Under a nitrogen atmosphere and at -20ºC, the dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt diether complex (2 mmol, 1 eq., 1.1 g) prepared above was dissolved in anhydrous diethyl ether (30 mL). While stirring, ZrCl4(THF)2 (2 mmol, 1 eq., 0.76 g) was added to the reaction flask. The reaction was carried out at -20ºC for 2 h, at room temperature for 2 h, and then heated to 50ºC for 16 h. After the reaction was complete, the solvent was removed under reduced pressure, toluene (100 mL) was added, and the mixture was heated to 60ºC and stirred for 1 h. The mixture was then hot-filtered. The filtrate was concentrated to 30 mL, and n-hexane (60 mL) was added. Crystals precipitated at 0ºC, filtered, and dried to obtain 1.14 g of a yellow solid, with a yield of 90%. NMR analysis showed that the solid was a mixture of RAC and Meso structured metallocene catalysts. Figure 1 ), NMR data 1 H NMR (500MHz, Chloroform- d ) δ 7.70 – 7.61 (m, 9.12 H, rac+meso), 7.58 – 7.54 (m, 4.38H, rac), 7.46 – 7.37 (m, 12.5H, rac+meso), 7.37 – 7.30 (m, 5H, rac+meso), 7.15 – 7.10 (m, 4.38H, rac+meso), 6.95 (s, 2.1H, rac), 6.89 (dd, J = 8.8, 6.9Hz, 2.25H, meso), 6.84 (s, 2.07H, meso), 2.46 (s, 6.24 H, meso), 2.26 (s, 6H,rac), 1.49 (s, 3.16H, meso), 1.35 (s, 6H, rac), 1.26 (s, 4.63H, meso). Example 2 Step 1. Preparation of the diethyl ether complex of dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt Proceed as step 1 of Example 1.

[0036] Step 2. Preparation of bridged metallocene compounds Under a nitrogen atmosphere and at -20ºC, a dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt diethyl ether complex (2.08 mmol, 1.04 eq., 1.15 g) was dissolved in anhydrous diethyl ether (20 mL). While stirring, ZrCl4(THF)2 (2 mmol, 1 eq., 0.76 g) was added to the reaction flask. The reaction was carried out for 2 h at room temperature for 2 h, then heated to 40ºC for 16 h. After the reaction was complete, the solvent was removed under reduced pressure, and toluene (100 mL) was added. The mixture was heated to 60ºC and stirred for 1 h, followed by hot filtration. The filtrate was concentrated to 30 mL by heating, and n-hexane (60 mL) was added. Crystals precipitated at 0ºC, were filtered, and dried to give 1.08 g of a yellow solid, with a yield of 86%, which was also a mixture of RAC and Meso structured metallocene catalysts.

[0037] Example 3 Step 1. Preparation of the diethyl ether complex of dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt Proceed as step 1 of Example 1.

[0038] Step 2. Preparation of bridged metallocene compounds Under a nitrogen atmosphere and at -10ºC, in a 100 mL reaction flask, the dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt diethyl ether complex (2 mmol, 1 eq., 1.1 g) was dissolved in anhydrous n-butyl ether (30 mL). While stirring, ZrCl4(THF)2 (2 mmol, 1 eq., 0.76 g) was added to the reaction flask. The reaction was carried out for 2 h, followed by 2 h at room temperature, and then heated to 50ºC for 20 h. After the reaction was complete, the solvent was removed under reduced pressure, and toluene (100 mL) was added. The mixture was heated to 60ºC and stirred for 1 h, followed by hot filtration. The filtrate was concentrated to 30 mL by heating, and n-hexane (60 mL) was added. Crystals precipitated at 0ºC, were filtered, and dried to give 0.99 g of a yellow solid, with a yield of 78%, which was also a mixture of RAC and Meso structured metallocene catalysts.

[0039] Comparative Example 1 Step 1. Preparation of dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt The difference from step 1 of Example 1 is that diethyl ether was not added; instead, dimethylsilylbis(2-methyl-4-phenyl-indene) was dissolved in 160 mL of toluene to obtain a yellow solid, namely dimethylsilylbis(2-methyl-4-phenyl-indene) dilithium salt.

[0040] Step 2. Preparation of bridged metallocene compounds Unlike step 2 of Example 1, the diethyl ether complex of dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt (2 mmol, 1 eq., 1.08 g) was replaced with dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt (2 mmol, 1 eq., 1.1 g). 0.76 g of a yellow solid (a mixture of RAC and Meso-structured metallocene catalysts) was obtained in 60% yield.

[0041] Comparative Example 2 Step 1. Preparation of the diethyl ether complex of dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt Proceed as step 1 of Example 1.

[0042] Step 2. Preparation of bridged metallocene compounds Under a nitrogen atmosphere and at -20ºC in a 100 mL reaction flask, the dimethylsilyl bis(2-methyl-4-phenyl-indenyl)dilithium salt diethyl ether complex (2 mmol, 1 eq., 1.1 g) was dissolved in anhydrous diethyl ether (30 mL). While stirring, ZrCl4(THF)2 (2 mmol, 1 eq., 0.76 g) was added to the reaction flask. The reaction was carried out at -20ºC for 2 h, then raised to room temperature and reacted for 18 h. After the reaction was complete, the solvent was removed under reduced pressure, and toluene (100 mL) was added. The mixture was heated to 60ºC and stirred for 1 h, followed by hot filtration. The filtrate was concentrated to 30 mL by heating, and n-hexane (60 mL) was added. Crystals precipitated at 0ºC, were filtered, and dried to give 0.66 g of a yellow solid (a mixture of RAC and Meso structure metallocene catalysts), with a yield of 53%.

[0043] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. 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 method for preparing a bridged metallocene compound, characterized in that, The preparation method includes the following steps: In the above equations (1)-(2): M is selected from titanium, zirconium, or hafnium; Q represents a silicon bridge or a carbon bridge; The two X's are the same or different, and are independently selected from halogens and carbon. 1~10 Alkyl and C 2~10 One or two of the alkenyl groups; R1, R2, R3, and R4 may be the same or different, and are independently selected from hydrogen, C, and C, respectively. 1~20 Alkyl, C 3~6 cycloalkyl and C 6~14 One or more of the aryl groups; R5 and R6 may be the same or different, and are independently selected from C. 1~10 Alkyl and C 6~14 One or two of the aryl groups; Step 1: Under an inert atmosphere, the compound of formula (1) is dissolved in an ether-containing solvent and reacted with alkyl lithium to obtain an ether complex of a bridged dilithium bis(lithium) salt. Step 2: Under an inert atmosphere, the ether complex of the bridged bis(lithium)-ceramic salt, MX4(THF)2 and ether are mixed and reacted under controlled temperature. After post-treatment, the bridged bis(lithium)-ceramic compound shown in formula (2) is obtained.

2. The preparation method according to claim 1, characterized in that, Each X is independently selected from F, Cl, Br, I, C. 1~4 Alkyl or C 2~6 alkenyl; And / or, R1, R2, R3, and R4 are independently selected from hydrogen, C, and C, respectively. 1~10 Alkyl, C 3~6 cycloalkyl or C 6~14 Aryl; And / or, R5 and R6 are each independently selected from C 1~4 Alkyl or C 6~10 Aryl.

3. The preparation method according to claim 1, characterized in that, The ethers in steps 1 and 2 may be the same or different, and are independently selected from C. 1~10 Alkyl ethers, such as C 1~4 Alkyl ethers, exemplified by one or more of diethyl ether, propyl ether, and butyl ether.

4. The preparation method according to claim 1, characterized in that, The ether-containing solvent is a mixture of ether and organic solvent (e.g., n-hexane or toluene); the volume percentage of ether in the ether-containing solvent is greater than 1 / 3.

5. The preparation method according to claim 1, characterized in that, The alkyl lithium is selected from C 1~6 Alkyl lithium, such as C 1~4 Alkyl lithium.

6. The preparation method according to claim 1, characterized in that, Step 1 includes: under a nitrogen atmosphere, dissolving the compound of formula (1) in an ether-containing solvent, adding n-butyllithium dropwise at a low temperature of -20ºC to 20ºC, reacting for 0.2 to 1 h after the addition is complete, then raising the temperature to room temperature and reacting for 8 to 15 h, removing the solvent under vacuum, adding hexane and stirring, filtering, washing, and drying to obtain the ether complex of the bridged dilithium bis(petroleum) salt.

7. The preparation method according to claim 1, characterized in that, The ether mentioned in step 2 is an anhydrous ether, such as one or more of anhydrous diethyl ether, anhydrous propyl ether, and anhydrous butyl ether.

8. The preparation method according to claim 1, characterized in that, Step 2: First, mix the ether complex of the bridged dilithium oxometalate salt and the ether at a low temperature of -40ºC to 10ºC to form a solution, and then add MX4(THF)2 to the solution.

9. The preparation method according to claim 1, characterized in that, The temperature-controlled reaction described in step 2 includes: first reacting at a low temperature of -40ºC to 10ºC for 1 to 3 hours, then raising the temperature to room temperature for 1 to 3 hours, and then heating to 40 to 80ºC for 6 to 20 hours.

10. The preparation method according to claim 1, characterized in that, The post-processing described in step 2 includes: after the reaction is completed, the solvent is dried under reduced pressure, toluene is added and heated to 50~70ºC, stirred and hot filtered; the filtrate is heated and concentrated, n-hexane is added, crystals are precipitated at low temperature of -5~5ºC, filtered, and the solid is dried to obtain the bridged biscenocene compound shown in formula (2).

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