Process for Preparing Metallocenes

Europaisches Patentamt European Patent Office © Publication number: 0 582 114A1 Office europeen des brevets

EUROPEAN PATENT APPLICATION

@ Date of filing: 16.07.93

© Priority: 03.08.92 US 923646 © Applicant: ETHYL CORPORATION 451 Florida Boulevard @ Date of publication of application: Baton Rouge, Louisiana 70801 (US) 09.02.94 Bulletin 94/06 @ Inventor: Lee, John Yuchu © Designated Contracting States: 1524 Stoneleigh Drive BE DE FR GB IT Baton Rouge, Louisiana 70808(US) Inventor: Diefenbach, Steven Paul 1457 Bullrush Drive Baton Rouge, Louisiana 7081 0(US)

© A process is provided for preparing a transition metal compound of the formula: (RC5r-U)2MX2, where R is hydrocarbyl or silahydrocarbyl of 1 to 10 carbon atoms, M is titanium or zirconium and X is halogen. The process comprises the steps of: (a) reacting Na(C5H5) with RX, where R and X are as defined above, in an organic solvent so as to form a reaction product mixture which includes RC5 m and C5 H5 ; (b) vacuum stripping the product mixture at ambient temperatures so as to remove substantially all of said C5 H5 from said product mixture; (c) deprotonating the RC5H4; and (d) adding MX+, where M and X are as defined < above, to the product mixture so as to react the RC5H4 and the MX+ and form said transition metal compound, the transition metal compound being substantially free of C5H5 containing impu- CM rities. 00

Rank Xerox (UK) Business Services (3. 10/3.09/3.3.4) 1 EP 0 582 114 A1 2

This invention relates generally to the prepara- said deprotonated RC5H4 and said MX+ and tion of metallocene derivatives which are useful as form said transition metal compound, said com- olefin polymerization catalysts and more specifi- pound being substantially free of C5H5 contain- cally to an improved process for preparing bis- ing impurities. (monosubstituted cyclopentadienyl) transition metal 5 According to the alkylation process, NaCp is metallocenes which are substantially free of unsub- reacted with an alkyl halide in a solvent. The NaCp stituted cyclopentadienyl impurities. is commercially available and can be prepared by Metallocene derivatives represented by the for- cracking cyclopentadiene dimer and reacting the mula (RCp)2MX2, where R is hydrocarbyl or cyclopentadiene with sodium metal as is known in silahydrocarbyl of 1 to 20 carbon atoms, Cp is 10 the art. The preferred alkyl halides are represented cyclopentadienyl (C5H4-), M is titanium or zirco- by the formula RX, where R is C1 to C2o (and more nium and X is halogen are known to be useful preferably C+ to C10) hydrocarbyl or silahydrocar- catalysts for olefin polymerization. They can be byl such as, for example, methyl, ethyl, n-propyl, prepared by reacting a deprotonated RCp com- isopropyl, n-butyl, tert-butyl, isobutyl, pentyl, hexyl, pound with MX4. As noted in the literature, how- 15 heptyl, or trimethylsilyl and X is halogen. Bromine ever, the generation of RCp by the alkylation of is the preferred halogen. Chlorine can be used but cyclopentadiene using alkyl halides is difficult due gives slower reaction rates and iodine is more to the generation of a complex mixture of products expensive. The NaCp and RX reactants are prefer- (Inorg. Chem. 1991, 30, 856-858). This reference ably used in NaCp:RX mole ratios of about 1:1, in proposes the use of either a liquid ammonia (low 20 order to minimize the amount of dialkyl substituted temperature) reaction medium or a highly reactive or unsubstituted Cp and Cp2 (cyclopentadiene alkylating agent, such as ethyl trifluoromethane- dimer) by-products, but ratios of 1:0.8 to 1:1.2 can sulfonate. Furthermore, the use of alkylhalides al- be used. The preferred solvents for the reaction are ways results in a product which contains, due to ethers (e.g., THF or diethylether but hydrocarbon the reaction equilibrium, cyclopentadiene and 25 solvents can also be used such as benzene or cyclopentadiene dimer. The dimer is inert in the toluene. Preferably, combined reactant concentra- subsequent metallocene preparation, but the tions of from 5 to 20 wt. percent in the solvent, are cyclopentadiene must be removed. Otherwise, it used. The reaction can be conducted at ambient will form (Cp)2MX2 impurities which adversely temperatures with the reaction being exothermic. change the molecular weight distributions of the 30 Generally, the reaction temperature will range from polymers produced when the (RCp)2MX2 metal- 20° to 50° C. The by-products of the alkylation locene product is used to catalyze olefin poly- reaction typically include besides NaCI, minor por- merization. Heretofore, complete removal of tions of R2Cp and Cp/(Cp2). Surprisingly, we have cyclopentadiene has not been achieved because of found that the Cp can be substantially completely the generation of additional cyclopentadiene due to 35 removed (less than about 1 wt. percent) by reduc- the cracking of the cyclopentadiene dimer. We ing the volume of the reaction mixture under vacu- have now discovered an economical, one-pot pro- um (2-15 mm Hg) at temperatures of 0° to 25° C. cess for making such transition metal metallocenes The cyclopentadiene dimer remains, but is inert so which are free of Cp impurities. Furthermore, the long as the subsequent reactions and product process can be conducted at ambient temperatures 40 work-up procedures avoid elevated temperatures which avoids the cost of refrigeration cooling sys- which would cause cracking to form additional tems. cyclopentadiene. The metallocene by-products re- In accordance with this invention there is pro- sulting from the presence of some disubstituted vided a process for preparing a transition metal cyclopentadiene (R2Cp) can be easily separated compound of the formula: (RC5r-U)2MX2, where R 45 from the final metallocene product by solvent sepa- is hydrocarbyl or silahydrocarbyl of 1 to 20 carbon ration. The vacuum treatment also removes any atoms, M is titanium or zirconium and X is halogen, unreacted alkyl halide which can then be recycled. said process comprising the steps of: Reduction of the volume of the reaction mixture to (a) reacting Na(C5H5) with RX, where R and X about 25% is sufficient to remove substantially all are as defined above, in an organic solvent so 50 of the cyclopentadiene (no Cp was detected by GC as to form a reaction product mixture which such that the Cp content was less than about includes RC5H4 and C5H5; 0.1%.) (b) vacuum stripping said product mixture at The product RCp can then be deprotonated in ambient temperatures so as to remove substan- situ with, for example, Na powder, BuLi, NaH, LiH tially all of said C5H5 from said product mixture; 55 or a Grignard reagent (RMgX). Solvent can be (c) deprotonating said RC5H4; and added back to the reaction mixture prior to de- (d) adding MX+, where M and X are as defined protonation. Preferably, about a 1:1 mole ratio of above, to said product mixture so as to react RCp to deprotonating agent is used. No more than

2 3 EP 0 582 114 A1 4

a 10% excess of deprotonating agent is necessary ml) was added slowly at 22 to 40 °C into above or desirable as we have found that salt formation BuBr/THF solution over a period of 15 minutes. with the mono-alkyl product is favored over the The reaction mixture was stirred at 22 ° C for 3 hrs. dialkyl (R2Cp) impurity. The deprotonation can be to form a mix-ture of BuCp (58 mol %), Bu2Cp (21 carried out at ambient temperatures and cooling is 5 mol %), Cp/(Cp)2 (21 mol %) based on NaCp unnecessary, although higher or lower tempera- charged, and a trace of BuBr. The volume of the tures of -30° C to 60° C can also be used. If above mixture was reduced under vacuum (0° to sodium is used as the deprotonating agent, then 22°C/2mm Hg) to 25% of its original volume. GC excess sodium metal must be filtered from the showed that all the cyclopentadiene and BuBr had reaction mixture prior to the further reaction with io been removed and there was 40 mol % of BuCp the transition metal halide to form the product bis- based on NaCp charged in the product mixture. (mono-alkylcyclopentadienyl) transition metal About 20 ml of THF were then added. Deprotona- metallocene. tion with a 10% excess amount of Na powder was The (RCp)2MX2 metallocene derivatives are performed. The Na was slowly added into above prepared by adding a transition metal halide of is solution at 22 °C over a period of 1/2 hr. Hydrogen titanium or zirconium, e.g., TiCk or ZrCk, to the formation was observed. The mixture was then deprotonated mono-alkylsubstituted cyclo-pen- stirred at 22 °C for an additional 2 hrs. 1HNMR of tadiene ligand, preferably in nearly stoichiometric the product showed a > 95% yield of NaBuCP. proportions of ligand to transition metal halide After the Na and NaBr were filtered out, the (mole ratios of 1 :0.4 to 0.5 ligand to transition metal 20 NaBuCp was further reacted with ZrCk (0.46 g, 2 halide and, more preferably, 1.0:0.5) so as to mini- mmol, dissolved in 4 g. of glyme) at 22 °C which mize the formation of RCpMX3 impurities and the was slowly added into the THF solution of NaBuCp amount of unreacted transition metal halide which in 5 minutes to form a > 90% yield (by 1HNMR) of may be difficult to remove from the product. The (BuCp)2ZrCb which contained no cyclopentadienyl process can be carried out at ambient temperature. 25 zirconocenes. The glyme and THF were removed Generally, the reaction temperatures range from and an equal volume of Et2 0 was added in order to 20 • to 40 • C. precipitate LiCI, which was then filtered out. Hex- When using sodium as the deprotonating ane (15 ml) was added, and the Et2 0 was slowly agent, it is preferable to add the transition metal stripped off at 40 to 45 °C. The hexane solution halide as a solvent solution in an ether solvent such 30 was cooled to 22 °C and (BuCp)2ZrCb crystallized. as glyme, diethylether or tetrahydrofuran (TNF). The product was filtered out, dried, and weighed. The sodium halide which is formed will precipitate The yield was 56% based on the BuCp used. The and can be filtered from the product solution. When 1HNMR showed that this product contained 6% BuLi is used as the deprotonating agent, LiCI is (Bu2Cp)2ZrCb but no cyclopentadienyl zir- soluble in tetrahydrofuran but not in diethylether so 35 conocenes. MP 89-92 °C (lit 93 °C). Pure product that the preferred reaction solvent is diethylether. can be obtained by further recrystallization. As an alternative when using BuLi, the alkyl cyclopentadiene reactant can be dissolved in Example 2 (Comparison) diethylether and the BuLi in hexane so as to form a slurry of LiRCp. The transition metal halide such as 40 BuCp (94% pure, 6.5 g, 0.05 mole) which was ZrCk powder or TiCk can then be added. LiCI will not prepared by the process of Example 1 , but was precipitate and can be removed by filtration. Upon purified by distillation and still contained 6% stripping the ether, the product (monoalkylCp)- cyclopentadiene, and 200 ml 2of Et2 0 were 2ZrCI2 product will crystallize from the hexane. An charged to a 500 ml flask in a dry-box. BuLi (0.05 advantage of the process of the invention is that it 45 mole, 3.2 g) in 20 ml of hexanes was added slowly can be carried out as a one-pot process without the with stirring into the above solution (temperature need to recover any intermediates. The products 22 ° to 33 ° C over a period of 30 minutes to form a can be recrystallized by dissolving them in warm very thick LiBuCp/Et2 0 slurry. The reaction mixture hexane (50 °C) and then cooling the hexane solu- was stirred at 22 °C for an additional 30 minutes. tion to precipitate the purified products. 50 1HNMR showed a 95% conversion. ZrCk powder The process is further illustrated by, but is not (0.025 mol) was directly added to the above slurry intended to be limited to, the following examples. with stirring (temperature 20° to 33 °C over a period of 30 minutes. The reaction mixture was stirred Example 1 at 22 °C for an additional 30 minutes. 1HNMR 55 showed a 95% formation of (BuCp)2ZrCb. In the BuBr (12 mmol, 1.644 g) and THF (6.0 g, 6.8 Et2 0/hexane solvent reaction medium, the LiCI was ml) were charged to a 50 ml r.b. flask in a dry box. 100% precipitated. The LiCI was filtered out, 40 ml A mixture of NaCp (10 mmol, 0.88 g) and THF (14 of hexane were added to the reaction mixture and

3 5 EP 0 582 114 A1 6 the Et2 0 was stripped off at 40-45 °C. The hexane 7. The process of claim 6 wherein said organic solution was cooled to 22 °C and (BuCp^ZrCb solvent is selected from the group consisting crystallized. The product (BuCp^ZrCb was filtered of ethers, hydrocarbons and any combination out, dried, and weighed. The yield was 74%. An thereof. additional 9% (BuCp^ZrCb was recovered from 5 the mother liquor. The product also contained 5% 8. The process of claim 7 wherein said solvent is cyclopentadienyl zirconocenes. The example illus- tetrahydrofuran, RX is n-butylbromide, MX+ is trates that the Cp impurity present in the starting ZrCk, the transition metal compound is bis-(n- BuCp will be carried through into the product butylcyclopentadienyl) zirconium dichloride, metallocene. The example also illustrates an al- io and said RC5H4 is deprotonated with a de- ternate method of deprotonation and product for- protonating agent selected from the group con- mation which can be used in the process of the sisting of Na, NaH, LiH, BuLi and a Grignard invention. reagent.

Claims 15 9. The process of claim 8 wherein said deprotonating agent is Na and said ZrCk is ad- 1. A process for preparing a transition metal com- ded as a solution in an ether solvent. pound of the formula: (RC5r-U)2MX2, where R is hydrocarbyl or silahydrocarbyl of 1 to 20 10. The process of claim 8 wherein said de- carbon atoms, M is titanium or zirconium and 20 protonating agent is BuLi in hexane, said or- X is halogen, said process comprising the ganic solvent is diethylether such that said steps of: BuLi and said R(C5r-U) form a slurry containing (a) reacting Na(C5H5) with RX, where R and UBUC5H4 and said ZrCk is added as a solid X are as defined above, in an organic sol- powder to said slurry to form said bis-(n-butyl- vent so as to form a reaction product mix- 25 cyclopentadienyl) zirconium chloride and LiCI, ture which includes RC5H4 and C5H5; which LiCI precipitates and is removed from (b) vacuum stripping said product mixture at the product solution. ambient temperatures so as to remove substantially all of said C5H5 from said product mixture; 30 (c) deprotonating said RC5 HU and (d) adding MX+, where M and X are as defined above, to said product mixture so as to react said deprotonated RC5H4 and said MX4 and form said transition metal 35 compound, said compound being substantially free of C5H5 containing impurities.

2. The process of claim 1 wherein said RC5H4 is deprotonated without recovering said RC5H4 from the reaction mixture.

3. The process of claim 1 wherein R is C+ to C1 0 hydrocarbyl and X is chlorine. 45 4. The process of claim 1 wherein the compound is bis(nbutylcyclopentadienyl) zirconium dichloride.

5. The process of claim 1 wherein the mole ratio 50 of Na(C5H5) to RX is from 1:0.8 to 1:1.2 and the mole ratio of deprotonated RC5H4 to MX+ is from 1:0.4 to 1:0.6.

6. The process of claim 5 wherein said product 55 mixture is vacuum stripped at a pressure of from 2-15 mm Hg and temperatures of 0 to 25 -C.

4 European Patent Number EUROPEAN SEARCH REPORT Application Office EP 93 11 1456

DOCUMENTS CONSIDERED TO BE RELEVANT Category Citation of document with indication, where appropriate, Relevant CLASSIFICATION OF THE of relevant passages to claim APPLICATION Jut. Cl.S ) INORGANIC CHEMISTRY C07F17/00 vol. 24, no. 16, 1985, pages 2539 - 2546 C.S. BAJGUR ET AL * page 2540, column 2 *

CHEMICAL ABSTRACTS, vol. 112, 1990, Columbus, Ohio, US; abstract no. 234837m, * ctbstrsict * & Z. NATURFORSCH . , B: CHEM. SCI, vol. 44, no. 10, 1989, pages 1293 - 1297 H. SITZMANN

TECHNICAL FIELDS SEARCHED ant. C1.5 )

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The present search report has been drawn up for all claims Place of search Date of completion of the search BERLIN 04 OCTOBER 1993 KAPTEYN H. CATEGORY OF CITED DOCUMENTS T : theory or principle underlying the invention E : earlier patent document, but published on, or X : particularly relevant if taken alone after the filing date Y : particularly relevant if combined with another D : document cited in the application document of the same category L : document cited for other reasons A : technological background O : non-written disclosure & : member of the same patent family, corresponding P : intermediate document document