Organometallic transition metal compound, biscyclopentadienyl ligand system, catalyst system and preparation of polyolefins

1. An organometallic transition metal compound of the formula (I):

where

M 1 is an element of group 3, 4, 5 or 6 of the Periodic Table of the Elements or the lanthanides;

the radicals X are identical or different and are each an organic or inorganic radical, with two radicals X also being able to be joined to one another;

m is 1 or 2;

n is a natural number from 1 to 4;

R 1 is hydrogen or an organic radical having from 1 to 40 carbon atoms;

R 3 is a substituted or unsubstituted C 6 -C 40 aryl radical;

R 4 is hydrogen, halogen or an organic radical having from 1 to 40 carbon atoms;

R 5 is an organic radical which has from 3 to 20 carbon atoms and is branched in the α position;

R 7 , R 8 are identical or different and are each hydrogen or an organic radical having from 1 to 40 carbon atoms or R 7 and R 8 together with the atoms connecting them form a monocyclic or polycyclic, substituted or unsubstituted ring system which has from 1 to 40 carbon atoms and optionally contains heteroatoms selected from the group consisting of the elements Si, Ge, N, P, O, S, Se and Te; and

A is a bridge consisting of a divalent atom or a divalent group.

2. The compound of claim 1 wherein R 1 and R 5 are different.

3. The compound of claim 1 wherein M 1 is a Group 4 transition metal and n=2.

4. The compound of claim 1 wherein R 7 , R 8 together form

where

R 9 , R 10 , R 11 and R 12 are identical or different and are each hydrogen, halogen or an organic radical having from 1 to 40 carbon atoms or two adjacent radicals R 9 , R 10 and/or R 11 together with the atoms connecting them form a monocyclic or polycyclic, substituted or unsubstituted ring system which has from 1 to 40 carbon atoms and optionally contains heteroatoms selected from the group consisting of the elements Si, Ge, N, P, O, S, Se and Te; and

A is a substituted silylene group or a substituted or unsubstituted ethylene group.

5. A biscyclopentadienyl ligand system of the formula (II):

or its double bond isomers,

wherein

m is 1 or 2;

R 1 is hydrogen or an organic radical having from 1 to 40 carbon atoms;

R 3 is a substituted or unsubstituted C 6 -C 40 aryl radical;

R 4 is hydrogen, halogen or an organic radical having from 1 to 40 carbon atoms;

R 5 is an organic radical which has from 3 to 20 carbon atoms and is branched in the α position;

R 7 , R 8 are identical or different and are each hydrogen or an organic radical having from 1 to 40 carbon atoms or R 7 and R 8 together with the atoms connecting them form a monocyclic or polycyclic, substituted or unsubstituted ring system which has from 1 to 40 carbon atoms and optionally contains heteroatoms selected from the group consisting of the elements Si, Ge, N, P, O, S, Se and Te; and

A is a bridge consisting of a divalent atom or a divalent group.

6. A catalyst system for the polymerization of olefins, which comprises:

(a) at least one organometallic transition metal compound of claim 1 ; and

(b) at least one cocatalyst which converts the at least one organometallic transition metal compound into a species which is polymerization-active toward at least one olefin.

7. The catalyst system of claim 6 further comprising a support.

8. A process which comprises polymerizing or copolymerizing at least one olefin in the presence of the catalyst system of claim 6 .

9. A process for preparing an organometallic transition metal compound, which comprises reacting the biscyclopentadienyl ligand system of claim 5 or a bisanion prepared therefrom with a transition metal compound.