| abstract |
A polymerization catalyst system is formed by combining an organometal compound and a transition metal compound to produce a catalyst A; and combining catalyst A and a catalyst B comprising a rare earth complex having a formula CpnMX4-n.M'Lx, wherein Cp is cyclopentadienyl or cyclopentadienyl substituted with an alkyl or alkyl silyl radical, M is yttrium, scandium or a rare earth metal having an atomic number in the range of 57 to 71, M' is an alkali metal, L is a suitable electron donor ligand, X is a halogen, n is 1 or 2, and x is a number corresponding to the value needed to form a stable complex. Optionally catalyst A is contacted with a rare earth metal halide. Optionally catalyst B is contacted with an alkali or alkaline earth metal alkyl. Optionally a hydrocarbyl aluminum compound can be contacted with catalyst B or with the catalyst system. |