Ligand effects on olefin polymerizations with multinuclear zirconocene catalysts having dimethylsilylferrocene as a cyclopentadienyl substituent

Olefin polymerizations were conducted with novel multimetallic zirconocene catalyst systems: R-CpCpZrCl₂ (1) (R = dimethylsilylferrocene; Cp = cyclopentadienyl) and (R-Cp)₂ZrCl₂ (2) in combination with methylaluminoxane or tetrakis(pentafluorophenyl) borates. In ethylene polymerization, the maximum catalyst activity was observed at a lower temperature (30-45°C) when using complex 1 or 2, compared with Cp₂ZrCl₂. It was also revealed that complex 1 is a more effective catalyst than Cp₂ZrCl₂ for copolymerization of ethylene and propene.