| abstract |
A very active catalyst system for olefin polymerization comprises a cocatalyst, preferably an aluminoxane, and a metallocene of the formula I or Ia (* CHEMICAL STRUCTURE *) in which, preferably, M1 is Zr or Hf, R1 and R2 are alkyl or halogen, R3 and R4 are hydrogen or alkyl, R5 and R6 are alkyl, -(CR8R9)m-R7-(CR8R9)n is a chain with one or more members, in which R7 can also be a (substituted) heteroatom, and m+n is zero or 1. |