Asymmetric silicon-bridged metallocenes useful as catalysts...

Details Asymmetric silicon-bridged metallocenes useful as catalysts... Asymmetric silicon-bridged metallocenes useful as catalysts...

2000-12-05

2003-03-25

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S160000, C526S943000, C526S351000, C526S352000, C556S011000

Reexamination Certificate

active

06538082

ABSTRACT:

TECHNICAL FIELD
The present invention relates to novel asymmetric silicon-bridged metallocenes useful as catalysts for the polymerization of &agr;-olefins. It relates more specifically to novel silicon-bridged metallocenes containing an indenyl and a partially or fully hydrogenated fluorenyl moiety and to a process for their preparation. Finally it relates to a process for polymerization of &agr;-olefins by using said asymmetric silicon-bridged metallocenes.
BACKGROUND OF THE INVENTION
Some asymmetric silicon-bridged metallocenes derived from group 4 metals and containing fluorenyl and indenyl moieties have already been proposed for the polymerization of &agr;-olefins such as ethylene and propylene. For example, the use of silicon-bridged (9-fluorenyl)-(1-substituted indenyl) zirconium dichlorides in combination with aluminoxanes for the polymerization of &agr;-olefins is disclosed in EP-A-0 754 698 and Macromolecules, 2000, 33 (5), 1546. However, the productivity and stability of such metallocenes remain insufficient.
Symmetric silicon-bridged bis(octahydrofluorenyl)zirconocenes and their use as catalysts for the polymerization of ethylene have been reported by Näsman et al. (J. Organomet. Chem., 1997, 545, 219) and are decribed in WO 95/27717. The latter also discloses the use of symmetric silicon-bridged bis(tetrahydrofluorenyl)zirconocenes. However, these zirconocenes are not suitable for the production of isotactic polypropylene.
Accordingly, there is still a need for silicon-bridged metallocene catalysts containing indenyl and fluorenyl moieties yielding very stereoregular polypropylene with high catalytic activity.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-mentioned problems by providing novel stable metallocenes useful as catalysts for &agr;-olefin polymerization which are, in particular, able to produce, with a particularly high activity, polyethylene and highly stereoregular polypropylene and a process for preparing such metallocenes. It is another object of the present invention to provide a process for polymerization of the &agr;-olefins by means of said metallocenes.
The invention is thus related to novel asymmetric silicon-bridged metallocenes of formula (I):
(SiR′R″)(C
p
)(C
p′
)MXX′  (I)
wherein
C
p
is a partially or fully hydrogenated fluorenyl moiety selected from those of formula (II) and (III)
C
p′
is an indenyl group selected from those of formula (IV)
M represents a transition metal selected from Ti, Zr and Hf,
X and X′ represent, same or different from each other, a halogen atom,
R
1
, R
2
and R
3
are, same or different from each other, an alkyl group containing 1 or 2 carbon atoms, an aryl group containing from 6 to 10 carbon atoms or a hydrogen atom,
(SiR′R″) is a divalent group which bridges the two groups C
p
and C
p′
repectively on position 9 and 1,
R′ and R″ are, same or different from each other, an alkyl or aryl group containing from 1 to 10 carbon atoms.
The invention also relates to a process for the preparation of these metallocenes.
Metallocenes of formula (I) wherein C
p
is a tetrahydrofluorenyl group selected from those of formula (II) are preferably prepared by a route comprising the following steps:
a) production of 9-(1,2,3,4-tetrahydrofluorenyl)-1-(indenyl (or substituted indenyl))-dialkyl(or diaryl)silane from the (indenyl (or substituted indenyl))-dialkyl(or diaryl)-chlorosilane and 1,2,3,4-tetrahydrofluorenyllithium,
b) production of the dilithium salt of 9-(1,2,3,4-tetrahydrofluorenyl) (1-indenyl (or substituted indenyl))-dialkyl(or diaryl)silane precursor and
c) production of the metallocene by reacting the said dilithium salt with a halide of one of the transition metals mentioned hereabove.
Metallocenes of formula (I) wherein Cp is an octahydrofluorenyl group of formula (III) are preferably prepared by a route comprising the following steps:
a′) production of 9-(1,2,3,4,5,6,7,8-octahydrofluorenyl)-1-(indenyl (or substituted indenyl))-dialkyl(or diaryl)silane from (indenyl (or substituted indenyl))lithium and 9-(1,2,3,4,5,6,7,8-octahydrofluorenyl) dichloro-dialkyl (or diaryl)silane,
b′) production of the dilithium salt of 9-(1,2,3,4,5,6,7,8-octahydrofluorenyl)-1-(indenyl (or substituted indenyl))-dialkyl(or diaryl)silane precursor and
c′) production of the metallocene by reacting the said dilithium salt with a halide of one of the transition metals mentioned hereabove.
Finally the present invention relates to a process for polymerization of &agr;-olefins by means of said metallocenes.
DETAILED DESCRIPTION
According to a first aspect, the present invention relates to novel stable metallocenes of the above general formula (I).
Preferably the transition metal is selected from hafnium and zirconium. Most preferably the transition metal is zirconium.
The halogen atoms X and X′ are preferably chlorine or bromine atoms and most preferably they are both chlorine atoms.
The group R
1
represents preferably a methyl group.
The groups R
2
and R
3
represent preferably a methyl group, an aryl group containing from 6 to 10 carbon atoms or a hydrogen atom, with at least one of R
2
or R
3
being different from hydrogen. Most preferably R
2
is a hydrogen atom and R
3
is a phenyl group.
The groups R′ and R″ are preferably alkyl groups and more particularly alkyl groups containing from 1 to 3 carbon atoms. Most preferably R′ and R″ are a methyl group.
Among the most preferred metallocenes according to the present invention belongs the dimethylsilylene-[&eegr;5-1-(2-methyl-4-phenyl)indenyl]-[&eegr;5-9-(1,2,3,4,5,6,7,8-octahydrofluorenyl)] zirconium dichloride. Another example of most preferred metallocenes according to the present invention is the dimethylsilylene-[&eegr;5-1-(2-methyl-4-phenyl)indenyl]-[&eegr;5-9-(1,2,3,4-tetrahydrofluorenyl)] zirconium dichloride.
When used in combination with a cocatalyst, such as for example aluminoxane, said novel stable metallocenes are able to produce with a high activity polyethylene and highly stereoregular polypropylene.
According to a second aspect, the present invention relates to a process for producing the novel metallocenes of general formula (I) as described hereabove.
Preferably, step (a) is carried out by reacting the 1,2,3,4-tetrahydrofluorenyllithium with the chlorosilane in equimolar quantity.
Preferably, step (b) is carried out with at least two molar equivalents of butyllithium per mole of the 9-(1,2,3,4-tetrahydrofluorenyl)-1-(indenyl (or substituted indenyl))-dialkyl(or diaryl)-silane precursor, followed by reacting the obtained dilithium salt with one equivalent of transition metal halide.
Preferably, the step (a) is carried out in an inert solvent such as diethylether or a mixture of these, most often at about 0° C. At the end of the reaction, the suspension is usually hydrolyzed and the organic phase is isolated. After removal of the solvent, the 9-(1,2,3,4-tetrahydrofluorenyl)-1-(indenyl (or substituted indenyl))-dialkyl(or diaryl)-silane precursor is isolated.
Preferably, step (b) is carried out in an inert solvent, such as diethylether, hexane, pentane or tetrahydrofuran (THF) often at 0° C. The resulting lithium salt is advantageously separated from the solvent and washed prior to being reacted, in step (c), with about one equivalent of a transition metal halide selected from halides of Ti, Zr and Hf.
Step (c) is preferably carried out in an inert solvent, such as an ether, often at 0° C. After removal of the solvent, the solid metallocene of formula (I) wherein C
p
is a group selected from those of formula (II) is isolated as a mixture of isomers.
Preferably, steps (a′), (b′) and (c′) are carried out in the same way as respectively the preferred steps (a), (b) and (c) for metallocenes of formula (I) wherein Cp is a group selected from those of formula (II). The 9-(1,2,3,4,5,6,7,8-octahydrofluorenyl)chloro-dialkyl(or diaryl)silane is generally synth

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