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

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

• where
• M1 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;
• R1 is hydrogen or an organic radical having from 1 to 40 carbon atoms;
• R3 is a substituted or unsubstituted C6-C40 aryl radical;
• R4 is hydrogen, halogen or an organic radical having from 1 to 40 carbon atoms;
• R5 is an organic radical which has from 3 to 20 carbon atoms and is branched in the α position;
• R7, R8 are identical or different and are each hydrogen or an organic radical having from 1 to 40 carbon atoms or R7 and R8 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.