| abstract |
A catalyst is prepared by combining a bis(cyclopentadienyl)zirconium compound with a second compound comprising a cation capable of donating a proton and a bulky, labile anion comprising a plurality of boron atoms capable of stabilizing the zirconium cation formally having a coordination number of 3 and a valence of +4 which is formed as a result of the combination. Many of the catalysts thus formed are stable and isolable and may be recovered and stored. The catalysts may be preformed and then used to polymerize olefins or the catalysts may be formed in situ during polymerization by adding the separate components to the polymerization reaction. The catalyst will be formed when the two components are combined at a temperature within the range from about -100C to about 300C. The catalysts thus prepared afford better control of polymer molecular weight and are not subject to equilibrium reversal. The catalysts thus produced are also less pyrophoric than the more conventional Ziegler-Natta olefin polymerization catalysts. |