| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | March 26, 1996 |
| PATENT TITLE |
Metallocene catalyst containing bulky organic group |
| PATENT ABSTRACT | An ionic metallocene catalyst for olefin polymerization which comprises: (1) a cyclopentadienyl-type ligand, a Group IVB transition metal, and alkyl, aryl, or hydride substituents, as a cation, and (2) a weakly coordinating anion comprising boron substituted with halogenated, such as tetra fluoro, aryl substituents preferably containing silylalkyl substitution, such as para-silyl t-butyldimethyl |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | March 10, 1994 |
| PATENT GOVERNMENT INTERESTS | This invention was made with Government support under Contract No. 86ER 13511 awarded by the Department of Energy. The Government has certain rights in this invention |
| PATENT CLAIMS |
We claim: 1. An ionic metallocene catalyst for olefin polymerization which comprises: (1) a cyclopentadienyl ligand, a Group IVB transition metal, and alkyl, aryl, or hydride substituents, as a cation, and (2) a weakly coordinating anion comprising boron substituted with four halogenated aryl substituents each containing a bulky organic substituent to improve the solubility and thermal stability of the catalyst as compared to a catalyst containing tetrakis (pentafluorophenyl) boron as the anion. 2. A catalyst as claimed in claim 1 wherein the aryl substituent in the anion (2) is selected from the group consisting of a phenyl, biphenyl, and naphthyl configuration. 3. A catalyst as claimed in claim 1 wherein the bulky organic substituent is selected from the group consisting of C.sub.1 to C.sub.20 alkyl and C.sub.1 to C.sub.20 alkyl-substituted group 14 metalloids. 4. A catalyst as claimed in claim 1 wherein the bulky organic substituent is an alkyl substituted silyl atom. 5. A catalyst as claimed in claim 1 wherein the substitution on the halogenated aryl substituents is silyl t-butyldimethyl. 6. A catalyst as claimed in claim 5 wherein the substitution is para- on the halogenated aryl substituents. 7. A catalyst as claimed in claim 1 wherein the aryl substituents contain four fluoro substituents. 8. A catalyst as claimed in claim 5 wherein the aryl substituents contain four fluoro substituents. 9. A catalyst as claimed in claim 6 wherein the aryl substituents contain four fluoro substituents. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
BACKGROUND OF THE INVENTION Metallocene cationic salts of the general type Cp.sub.2 MR.sup.+ X.sup.- (Cp being a cyclopentadienyl-type ligand; M being a Group IVB metal such as titanium, zirconium, or hafnium, R being alkyl, aryl or hydride; and X being a weakly coordinating anion form the basis for a large family of active, efficient and selective olefin polymerization catalysts. The performance of these systems is exceedingly sensitive to the nature of X.sup.- with X.sup.- being, preferably, RMAQ- (MAO being methylaluminoxane), RB(C.sub.6 F.sub.5).sub.3.sup.-, and B(C.sub.6 F.sub.5).sub.4.sup.-. While B(C.sub.6 F.sub.5).sub.4.sup.- appears to give the most active catalysts, such catalysts suffer from insolubility and thermal instability. U.S. Pat. No. 5,153,157to G. G. Hlatky et al. discloses catalyst systems in which the anion is said to be bulky, labile and non-coordinateable with the Group IV metallocene containing component. Despite a rather generalized disclosure of possible substitution possibilities on the aromatic hydrocarbon groups of the anion, this patent only exemplifies the use of tetraphenyl borate and tetrapentafluorophenyl borate species without any suggestion that the presence of certain types of substitution on these structures would yield systems having enhanced solubility and thermal stability characteristics. There is, furthermore, no enabling description as to how such enhanced systems might be made. DESCRIPTION OF THE INVENTION The present invention relates to a modification of the aforementioned type of catalyst systems by providing a weakly coordinating anion comprising boron substituted with halogenated aryl substituents containing silylalkyl substitution. The presence of silylalkyl substitution on the aryl moiety, preferably in the para-position increases the solubility and thermal stability of the resulting metallocene salts. It is within the contemplation of the present invention that a variety of general boron-containing structures can be employed in accordance with the present invention. For example, boron tetraaryl structures in which the four aryl groups are phenyl containing four fluorine substituents and a bulky "R" group in the ortho, meta or para-position to increase the solubility and thermal stability of the catalyst system are contemplated herein. Representative R groups include C.sub.1 to C.sub.20 alkyl or C.sub.1 to C.sub.20 alkyl-substituted group 14 metalloids (e.g., silicon, germanium, or tin). Also contemplated are analogous boron species where the aryl moiety can comprise a biphenylene structure in which the phenyl ring closest to the boron atom contains four fluorine substituents with the more remote phenyl ring containing four fluorine substituents and the type of R group defined above. If desired, the biphenylene configuration of the aryl substituents can be reconfigured to a naphthyl configuration with the same type of R group being used to improve the solubility and thermal stability of the catalyst that results as compared to one not containing the bulky R substituent. The silylalkyl substitution, which represents a preferred embodiment herein, is of the structure with R.sup.l being the same or different and being selected from straight and branched alkyl, preferably lower alkyl of from one to four carbon atoms. Representative alkyl groups include methyl, ethyl and t-butyl. A particularly preferred silyl substituent comprises one t-butyl and two methyl groups in aryl substituents also containing four fluorine atoms. The thermal stability for such a system is significant since it has been found stable with no significant thermal decomposition to 100.degree. C. over a period of hours. In contrast, the known system Cp.sub.2 "ZrCH.sub.3.sup.- B(C.sub.6 F.sub.4).sub.4.sup.-, Cp" being 1,2-dimethylcyclopentadienyl) is only stable below 0.degree. C. for significant periods of time. The general type of procedure for making the desired metallocene catalyst of the present invention can be practiced by using the general type of procedure disclosed in Examples 1-4, below, which depict the synthesis of a particularly preferred embodiment of the invention. Initially, a precursor for the anion can be formed, for example, by reaction of a halogenated benzene analog of the ultimately desired, non-silyl substituted structure, a suitable metallating agent, such as an alkyl lithium reagent, and a silylalkyl trifluoromethane sulfonate. The resulting reaction forms the desired silylalkyl-substituted halogenated benzene precursor for the subsequent step in which such a precursor is reacted with a suitable metallating agent, such as an alkyllithium reagent, and boron trihalide to form a lithium and borate-containing salt species which is in turn reacted with triphenylmethyl chloride to form the triphenyl carbenium precursor. This resulting precursor can be reacted with a selected bis(cyclopentadienyl) zirconocene reagent to form the ultimately desired catalyst salt. If desired, the catalyst salt can be generated in-situ by mixing the desired metallocene (e.g. ,Cp.sub.2 Zr(CH.sub.3).sub.2) and boron-containing reagent (e.g., B(R).sub.3, where R is preferably a silyl-substituted tetrafluorophenyl group) just prior to polymerization. |
| PATENT EXAMPLES | Available on request |
| PATENT PHOTOCOPY | Available on request |
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