Process for producing metallocenes

Abstract

The invention relates to a method for producing metallocenes. The present invention relates to an improved process for the preparation of metallocenes of general formula (A) CR2L2MX2, and to intermediates useful in the synthesis of said metallocenes and to the use of said metallocenes as catalysts in the polymerization of olefins.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 202080010822.1, titled "Method for Producing Metallocenes", with a filing date of January 27, 2020. Technical Field

[0002] The present invention relates to an improved method for preparing metallocenes of the general formula (A) CR2L2MX2, and to intermediates useful for synthesizing said metallocenes and the use of said metallocenes as catalysts in olefin polymerization. Background Art

[0003] The polymerization of olefins such as ethylene and propylene for the manufacture of thermoplastics or norbornene-containing polymers generally uses transition metal compounds, especially metallocene compounds, as polymerization catalysts. In the past few decades, such polymerization catalysts have been variously modified and studied.

[0004] For example, metallocene compounds containing unsubstituted or alkyl-substituted indenyl or fluorenyl ligand systems are known (GB-A-934,281).

[0005] As is generally known in the art, bridged and substituted bis-(1-indenyl) ligands are suitable for use as starting compounds in methods for producing metallocene catalysts for olefin polymerization.

[0006] US-A-6,072,085 discloses 2,2-bisindenylpropane as a carbon-bridged substituted dicyclopentadiene compound.

[0007] EP-A-0 485 823 and EP-A-0 563 917 disclose zirconium-based metallocenes (so-called metallocene zirconiums) containing bridged indenyl derivatives as ligands.

[0008] In Metalorganic Catalysts for Synthesis and Polymerization, 1999, page 462 (Walter Kaminsky), and in EP-A-0 511 665, isopropylidene-bis-(1-indenyl) zirconium dichloride and isopropylidene-bis-(1-fluorenyl) zirconium dichloride are disclosed.

[0009]

[0010] However, the production of such bridged metallocene compounds in a more efficient manner and in high yields has been a subject of interest.

[0011] EP-A-0 416 566 discloses a process for producing 2,2-bis(1-indenyl)propane. Indene is reacted with n-butyllithium and then 1-isopropylindene is added to produce 2,2-bis(1-indenyl)propane.

[0012]

[0013] 2,2-Bis(1-indenyl)propane is further reacted with n-butyllithium and then a solution of zirconium chloride in dichloromethane is added to produce isopropylidene-bis-(1-indenyl)zirconium dichloride. The orange precipitate is filtered, washed with dichloromethane and dried. The yield of 2,2-bisindenylpropane is 39%.

[0014] EP-A-0 722 949 discloses a process for producing 2,2-bis(1-indenyl)propane. Indene is added to a suspension of potassium hydroxide (KOH) and dimethoxyethane (DME), and acetone is added dropwise. The resulting mixture is treated with dilute phosphoric acid and diethyl ether. The organic phase is separated, washed and dried over Na2SO4.

[0015] EP-A-0 722 950 discloses a process for producing bridged metallocenes such as racemic-isopropylidene-bis(indenyl)zirconium dichloride. 2,2-Bis(indenyl)propane is dissolved in diethyl ether and treated with n-BuLi in pentane. The suspension is treated with triethylstannyl chloride and then ZrCl4 is added to the separated organic phase.

[0016] EP-B-0 751 143 discloses a process for producing 2,2-bisindenylpropane and isopropylidene-bis-(1-indenyl)zirconium dichloride. Indene is dissolved in toluene and an aqueous solution of sodium hydroxide (NaOH) and a phase transfer catalyst triethylbenzylammonium chloride (TEBA) is added. Then acetone is added dropwise. The aqueous phase is separated and extracted twice with diethyl ether. Finally, the organic phase is dried over MgSO4 and the solvent is removed under vacuum. The yield of 2,2-bisindenylpropane is 85%.

[0017]

[0018] Furthermore, a metallization step as a next step is disclosed in EP-A-0 751 143, giving a 55% separated product. 2,2-Bisindenylpropane is reacted with n-butyllithium (BuLi) in diethyl ether. After adding hexane, the suspension is filtered and washed with pentane. The dilithium salt precipitate is dried and added to a suspension of ZrCl4 in dichloromethane.

[0019] However, for commercial purposes, the yields are not satisfactory. In addition, traces of the phase transfer catalyst triethylbenzylammonium chloride and impurities remain in the product and interfere with subsequent reactions.

[0020] JP 4108334 discloses a method for producing 2,2-bisindenylpropane derivatives having a substituent at the 2-position (via an isopropylidene-bis(2-bromo-1-indene) intermediate) and their metallocenes, such as isopropylidene-bis(2-methyl-1-indenyl)zirconium dichloride.

[0021] As described above, many studies have been conducted on metallocene compounds as catalysts for producing olefin polymers and their production methods. Although progress has been made so far, there is still room for improvement in the methods for producing metallocene catalysts. In particular, in order to establish a synthetic route that can be easily scaled up, a reproducible synthetic route and method are necessary.

[0022] In addition to being reproducible, an efficient production method, i.e., an economical method, is also sought in terms of the conversion of starting materials, the use of solvents and catalysts, and the number of synthetic steps. Summary of the Invention

[0023] As outlined above, it can be seen that the object to be solved by the present invention is to provide an improved method for producing a metallocene such as isopropylidene bis-(1-indenyl)zirconium dichloride of the general formula (A) CR2L2MX2.

[0024] The present invention provides a method for preparing a metallocene of the general formula (A)

[0025] CR2L2MX2 (A)

[0026] The method comprises the following steps:

[0027] (a) reacting a symmetric or asymmetric, straight-chain or cyclic ketone of the general formula (B) (C═O)R2 with a ligand L in the presence of an alkali metal alkoxide M 1 OR 1 to form a compound of the general formula (C) CR2L2; and

[0028] (b) reacting the compound (C) CR2L2 with a metal halide MX4 in the presence of a deprotonating agent,

[0029] wherein

[0030] R is independently a C1-C8 alkyl, cycloalkyl or phenyl group, preferably methyl, ethyl, propyl or phenyl, more preferably methyl or phenyl,

[0031] R 1 is a C1-C 20 alkyl group, preferably a C1-C6 alkyl group, more preferably methyl or ethyl,

[0032] L is independently an unsubstituted indenyl, substituted indenyl, unsubstituted benzoindenyl, substituted benzoindenyl, unsubstituted fluorenyl or substituted fluorenyl, preferably an unsubstituted indenyl, unsubstituted fluorenyl or unsubstituted benzoindenyl, and more preferably an unsubstituted indenyl,

[0033] M is zirconium, hafnium, titanium or a lanthanide element, preferably zirconium or hafnium, more preferably zirconium,

[0034] M 1 is an alkali metal, preferably lithium, sodium or potassium, more preferably sodium, and

[0035] X is a halogen, preferably chlorine or bromine, more preferably chlorine.

[0036] Furthermore, the present invention provides the use of a metallocene of general formula (A) obtained according to the present invention as a catalyst in olefin polymerization.

[0037] These and other features and advantages of the present invention will be apparent from the following detailed description and claims. Detailed Description

[0038] Throughout this specification and claims or items, unless the context otherwise requires, the word "comprise" and variations such as "comprises" and "comprising" will be understood to imply the inclusion of the stated integer (or step) or group of integers (or steps).

[0039] The present invention relates to a method for producing a metallocene of general formula (A) CR2L2MX2, preferably diisopropylidene bis-(1-indenyl) zirconium dichloride.

[0040] Furthermore, the present invention provides the use of the metallocene of general formula (A) CR2L2MX2, preferably diisopropylidene bis-(1-indenyl) zirconium dichloride, as a polymerization catalyst for olefins.

[0041] Reaction step (a) - Preparation of a compound of general formula (C) CR2L2

[0042] A method for producing a metallocene of general formula (A) CR2L2MX2 such as diisopropylidene bis-(1-indenyl) zirconium dichloride includes a first step (a) in which a symmetric or asymmetric, straight-chain or cyclic ketone of general formula (B) (C=O)R2 and a ligand L react in the presence of sodium methoxide or sodium ethoxide to form a compound of general formula (C) CR2L2.

[0043] Ketone (B) (C=O)R2

[0044] The ketones of the general formula (B)(C=O)R2 are symmetric or asymmetric, straight-chain or cyclic ketones, where R is independently a C1-C8 alkyl group, cycloalkyl group or phenyl group, preferably methyl, ethyl, propyl or phenyl, more preferably methyl or phenyl. R can be linked to form a 3- to 7-membered cyclic ring.

[0045] In a preferred embodiment, the ketone (B) is acetone, benzophenone, acetylbenzophenone or cyclohexanone, more preferably acetone or benzophenone.

[0046] Ligand L

[0047] Ligand L is independently an unsubstituted indenyl group, substituted indenyl group, unsubstituted benzoindenyl group or substituted benzoindenyl group, preferably an unsubstituted indenyl group, unsubstituted fluorenyl group or unsubstituted benzoindenyl group, and more preferably an unsubstituted indenyl group.

[0048] In the present invention, the term "substituted" means C1-C 20 alkyl-substituted or C1-C 20 aryl-substituted.

[0049] Preferred examples of the substituted indenyl ligands are 4,5,6,7-tetrahydro-1-inden, 3-methylinden, 3-tert-butylinden, 3-trimethylsilylinden or 4-phenylinden.

[0050] Preferred examples of the substituted benzoindenyl ligands are 4,5-benzoinden, 2-methyl-4,5-benzoinden, 2-methyl-α-acenaphthindene or 2-methyl-4,6-diisopropylinden.

[0051] In a preferred embodiment of the present invention, only one type of ligand L is used in reaction step (a) and no mixture is used.

[0052] Alkali metal alkoxide M 1 OR 1

[0053] The first reaction step (a) of the present invention is carried out in the presence of an alkali metal alkoxide M 1 OR 1 where

[0054] R 1 is a C1-C 20 alkyl group, preferably a C1-C6 alkyl group, more preferably methyl or ethyl, most preferably methyl, and

[0055] M 1 is an alkali metal, preferably lithium, sodium or potassium, more preferably sodium.

[0056] In a preferred embodiment, the reaction is carried out in the presence of an alkali metal methoxide or an alkali metal ethoxide. In a more preferred embodiment, the reaction is carried out in the presence of sodium methoxide or sodium ethoxide. In a most preferred embodiment, the reaction is carried out in the presence of sodium methoxide.

[0057] In a preferred embodiment, the reaction of the first reaction step (a) comprises the reaction of acetone with sodium methoxide and unsubstituted indene in dimethyl sulfoxide (DMSO), and can be summarized as follows:

[0058]

[0059] In a preferred embodiment of the present invention, the compound of formula (C) is 2,2 - bis(indenyl)propane.

[0060] According to the present invention, it has been found that by using sodium methoxide or sodium ethoxide as the base in the first reaction step, the formation of the compound of formula (C) CR2L2, preferably the intermediate 2,2 - bis(indenyl)propane, can be achieved in much higher yields and without the presence of by - products such as sodium indenide, oxidation products of sodium indenide, or polymerization products, which are typically obtained when using alkali metal hydroxides (such as sodium hydroxide or potassium hydroxide) as the base.

[0061] In particular, when using sodium hydroxide, it has been found that the yield of the intermediate 2,2 - bis(indenyl)propane varies significantly, and in some test reactions, no 2,2 - bis(indenyl)propane product is even produced. In addition, when using sodium hydroxide, it is difficult and / or cumbersome to remove the by - products from the desired product, i.e., 2,2 - bis(indenyl)propane.

[0062] Furthermore, according to the present invention, it has been found that when using dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) as the solvent in the reaction of a symmetric or asymmetric, straight - chain or cyclic ketone and indene, a high product yield of, for example, greater than 60%, more preferably greater than 70% of the isolated product of 2,2 - bis(indenyl)propane can be obtained.

[0063] In an even more preferred embodiment, the reaction of the symmetric or asymmetric, straight - chain or cyclic ketone (B) and indene is carried out by adding the symmetric or asymmetric, straight - chain or cyclic ketone (B) to a reaction mixture containing indene and dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) (preferably DMSO).

[0064] In an even more preferred embodiment, the reaction of the symmetric or asymmetric, straight - chain or cyclic ketone (B) and the ligand L as described above is carried out at a temperature of 0 °C to 40 °C, more preferably 0 °C to 25 °C, even more preferably 5 °C to 15 °C for a period of 10 minutes to 30 minutes.

[0065] In a preferred embodiment, the reaction mixture is additionally stirred at a temperature below 40 °C for 1 to 120 minutes.

[0066] After running this reaction, the reaction mixture is typically worked up, for example by adding methyl tert-butyl ether (MTBE) and / or water and / or 10% NaCl solution in order to quench the reaction mixture. The organic phase is separated by phase separation and the organic phase is washed with water. Thereafter, the organic phase is typically dried, for example by adding sodium sulfate (Na2SO4). Subsequently, the organic phase can be subjected to a distillation step in order to purify the product 2,2-bisindenylpropane.

[0067] In a preferred embodiment, the reaction of step (a) is carried out in the absence of any phase transfer catalyst.

[0068] As shown above, according to the present invention, a second reaction step (“metalation”) is then carried out.

[0069] Reaction step (b) - Preparation of metallocenes of the general formula (A) CR2L2MX2

[0070] In the second step (b) of the process according to the invention, a compound of the general formula (C) CR2L2 is reacted with a metal halide MX4 in the presence of a deprotonating agent in order to form a metallocene of the general formula (A) CR2L2MX2, preferably diisopropylidene-bis-(1-indenyl) zirconium dichloride.

[0071] Metal halide MX4

[0072] X of the metal halide MX4 is a halogen, preferably fluoride, chloride, bromide or iodide, more preferably chloride.

[0073] M of the metal halide MX4 is zirconium (Zr), hafnium (Hf), titanium (Ti) or a lanthanide such as neodymium.

[0074] The metal halide MX4 is preferably ZrF4, ZrCl4, ZrBr4, ZrI4, HfCl4, TiCl4, or NdCl3, more preferably ZrCl4.

[0075] Deprotonating agent

[0076] In the present invention, typical deprotonating agents can be used. Preferably, the deprotonating agent is n-butyllithium (n-BuLi), sodium hydride (NaH), BEM or BOMAG, more preferably n-BuLi. In a preferred embodiment, a deprotonating agent highly soluble in tetrahydrofuran (THF) is used.

[0077] In a preferred embodiment of the present invention, the second reaction step (b) is carried out by using tetrahydrofuran (THF), methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), methyltetrahydrofuran, di-n-butyl ether, or diisopropyl ether (DIPE), more preferably a mixture of THF and hexane as the solvent.

[0078] In a preferred embodiment of the present invention, the second step (b) is carried out by using an n-BuLi solution in hexane having a concentration of 80% or greater, preferably 90% or greater. An n-BuLi concentration less than 80% (such as a commercially available solution of only 20%) is not preferred because the amount of hexane becomes high, which results in the precipitation of LiCl.

[0079] In a preferred embodiment, the ligand L is first dissolved in a solvent, preferably in THF, MTBE, ETBE, TAME, or DIPE, and then a deprotonating agent and a metal halide MX4 are added to the mixture.

[0080]

[0081] Generally, the second reaction step (b) is carried out by adding MX4 to the compound (C) CR2L2 at a temperature of 0 to -20 °C, more preferably -5 °C to -15 °C, for a period of 15 minutes to 10 hours, more preferably 30 minutes to 5 hours.

[0082] Preferably, the second reaction step (b) is carried out by adding zirconium(IV) chloride to the intermediate dilithium salt of 2,2-bis(indenyl)propane at a temperature of 0 to -20 °C, more preferably -5 °C to -15 °C, for a period of 15 minutes to 10 hours, more preferably 30 minutes to 5 hours.

[0083] The inventors of the present invention have found that a high yield of the final product can be achieved by using THF as the solvent in the second reaction step because in such a case, the by-product LiCl formed in the second reaction step does not have to be removed in an additional step because it is soluble in THF while the product is insoluble in THF and thus precipitates.

[0084] As is known in the art, the polymerization yield of olefins in the presence of a metallocene catalyst such as isopropylidene bis-(1-indenyl)zirconium dichloride depends on the purity of the metallocene catalyst. When isopropylidene bis-(1-indenyl)zirconium dichloride obtained by the method claimed in the present invention is used as the metallocene catalyst in olefin polymerization, a high polymerization yield can be unexpectedly achieved.

[0085] In a preferred embodiment of the present invention, the metallocene of general formula (A) CR2L2MX2 is symmetric.

[0086] According to another aspect of the present invention, the metallocene of general formula (A), preferably diisopropylidene bis-(1-indenyl) zirconium dichloride, produced by any method according to the present invention, is used as a catalyst in olefin polymerization.

[0087] Examples

[0088] Example 1:

[0089] Reaction step (a) Synthesis of 2,2-bis(indenyl)propane

[0090] All operations were carried out under an inert gas atmosphere (argon). DMSO (100 mL), NaOMe (0.9 g, 0.02 mol), and indene (40 g, 0.33 mol) were charged into a 2 L volume double-walled reactor and stirred at 20 °C for 30 minutes. The reactor was cooled to 10 °C. Then, acetone (9.7 g, 0.17 mol) was added over 15 minutes such that the reactor temperature was kept below 20 °C (exothermic reaction). Then, the reaction mixture was stirred at 40 °C for 2 h and stirred overnight at room temperature until the reaction was complete (judged by GC, 6,6-dimethylfulvene < 1%). 100 g of water was added at 10 °C and stirred for 30 minutes, then methyl tert-butyl ether (MTBE; 236 g) was added to the reaction mixture. The mixture was stirred at room temperature for another 30 minutes.

[0091] The two phases were separated, the aqueous phase was extracted again with MTBE, and the combined organic phases were washed with saturated aqueous NaCl solution (2 × 100 mL) until neutral. The organic phase was dried over Na2SO4, and then MTBE and unreacted indene were removed by vacuum distillation at up to 40 °C almost to dryness. The remaining thick suspension was filtered, and the crude product was washed with methanol, hexane, and MTBE. Drying yielded a brown crystalline solid (27 g) with a purity of 98.4%. Additional treatment of the remaining mother liquor similar to the separation step yielded an additional 10 g of pure product. The total yield was 37 g, 81%.

[0092]

[0093] Reaction step (b) Preparation of isopropylidene bis(1-indenyl)zirconium dichloride

[0094] All operations were carried out under an inert gas atmosphere. In a 2 L volume double-walled reactor, 2,2-bis(indenyl)propane (15.8 g, 0.056 mol, purity 98.6%) of reaction step (a) was dissolved in tetrahydrofuran (THF; 200 mL) at room temperature and the mixture was cooled to -5 °C. n-BuLi (90% solution in n-hexane, 8.06 g, 0.1120 mol) was added within 30 min such that the reactor temperature was kept below 7 °C. The solution was stirred at 0 °C for 60 min. The dilithium salt of the ligand was precipitated. The suspension was warmed to room temperature and stirred for a further 120 min at 25 °C. Then, the solution was cooled again to 0 °C and ZrCl4·2THF (21.15 g, 0.056 mol) was added. The addition was exothermic, with the temperature rising by about 10 - 20 K. The reaction mixture was warmed to 20 °C and stirred overnight. The dark red product was precipitated after 120 min. The product was separated by filtration and washed twice with THF and twice with hexane / THF to remove residual traces of LiCl. The product was dried in vacuo, yielding 16.6 g (0.038 mol, 67.8% i.y) of fine orange to red crystals.

[0095]

[0096] Example 2:

[0097] Example 2 was carried out in the same manner as Example 1, except that the bridge was replaced with benzophenone (O = CPh2; 15.2 g, 0.08 mol) as shown in Table 1, and the amount of NaOMe was doubled. The product was dried in vacuo, yielding 35.5 g (0.064 mol, 80.1% i.y) of fine orange to red crystals.

[0098] Example 3:

[0099] Example 3 was carried out in the same manner as Example 1, except that DMF (dimethylformamide) was used as the solvent as shown in Table 1. The product was dried in vacuo, yielding 20.0 g (0.073 mol, 44.2%) of fine white crystals.

[0100] Example 4 (scaled up):

[0101] A reactor with a volume of one cubic meter was conditioned with an inert gas atmosphere, and DMSO (120 kg, 1536 mol) and NaOMe (1.01 kg, 20 mol) were added to the reactor. 42.4 kg of indene was added to the stirred suspension and the reaction mixture was stirred at 20 °C for 30 minutes. The mixture was cooled to 10 °C and acetone (10.6 kg, 180 mol) was added within 10 minutes. The reactor was further cooled to maintain the temperature below 40 °C. After the addition was complete, the reaction mixture was heated to 40 °C and stirred at this temperature for 1 hour. After sampling, the reaction mixture was cooled to 20 °C and stirred at 20 °C for 12 hours. 258 kg of MTBE was added to the reaction mixture, followed by the exothermic addition of 118 kg of 10% NaOH solution at 0 °C. The temperature rose to about 20 °C and the resulting biphasic mixture was stirred for at least 30 minutes. The phases were separated, the organic phase was washed again with 120 kg of MTBE, the combined organic phases were dried over Na2SO4 and poured back into the reactor. Approximately 85% of the MTBE was distilled off at 40 °C, the same amount of heptane was added and distilled again. The remaining suspension was cooled to 20 °C, filtered through a filter press and washed with a 1:1 mixture of methanol / heptane. The product was dried in vacuo to yield 30 kg (110.1 mol, 59.4%) of a brownish powder with a purity greater than 96%.

[0102] Table 1: Metallocene Ligand Composition

[0103] Number L1 L2 Bridge NaOMe Solvent Yield 1 Ind Ind <![CDATA[O=CMe2]]> 0.05 equivalent DMSO 67.8％ 2 Ind Ind <![CDATA[O=CPh2]]> 0.1 equivalent DMSO 80.1％ 3 Ind Ind <![CDATA[O=CMe2]]> 0.05 equivalent DMF 44.2％ 4 Ind Ind <![CDATA[O=CMe2]]> 0.05 equivalent DMSO 59.4％

[0104] Ind = indenyl ligand

[0105] O = CMe2 = acetone

[0106] O = CPh2 = benzophenone.

Claims

1. A method for preparing a metallocene of the general formula (A) CR2L2MX2 (A) The method comprises the following steps: (a) React a symmetric or asymmetric, straight-chain or cyclic ketone of the general formula (B) (C=O)R2 with a ligand L in the presence of an alkali metal alkoxide M 1 OR 1 to form a compound of the general formula (C) CR2L2; wherein the reaction step (a) is carried out in dimethyl sulfoxide; and (b) reacting the compound (C) CR2L2 with a metal halide MX4 in the presence of a deprotonating agent, wherein the deprotonating agent is an n-BuLi solution in hexane with a concentration of 80% or greater, wherein R is independently a C1-C8 alkyl, cycloalkyl or phenyl group, R 1 is C1-C 20 alkyl group, L is independently an unsubstituted indenyl, substituted indenyl, unsubstituted benzoindenyl, substituted benzoindenyl, M is zirconium or hafnium, M 1 is an alkali metal, and X is a halogen.

2. The method according to claim 1, wherein R is independently methyl, ethyl, propyl or phenyl.

3. The method according to claim 1, wherein, R is independently methyl or phenyl.

4. The method according to claim 1, wherein R 1 is a C1-C6 alkyl group.

5. The method according to claim 1, wherein, R 1 is methyl or ethyl.

6. The method according to claim 1, wherein, L is independently an unsubstituted indenyl or unsubstituted benzoindenyl.

7. The method according to claim 1, wherein, L is independently an unsubstituted indenyl.

8. The method according to claim 1, wherein M is zirconium.

9. The method according to claim 1, wherein M 1 is lithium, sodium or potassium.

10. The method according to claim 1, wherein, M 1 is sodium.

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