Control of symmetry in active cationic ansa-zirconocene species: Catalyst preparation, characterization and ethylene-norbornene copolymerization

Article abstract of DOI:10.1016/j.jorganchem.2004.08.013

New bis-hydrocarbyl complexes of methylene bridged ansa-metallocenes [H₂Me₂H₂)₂]ZrR₂ {R = Me (1), CH₂Ph (2), CH₂SiMe₃ (3), Ph (4)} have been prepared. They form catalytically active intermediates with borane or borate depending on solvent and Zr-R group. Specifically, [H₂C(Me₂C₅H₂)₂] Zr(CH₂Ph)₂ (2) produced an ion pair upon treatment with B(C₆F₅)₃ whereas [H₂ C(Me₂C₅H₂)₂]Zr(CH₂ SiMe₃)₂ (3) produced a zwitterionic species, identified by ¹H,¹³C, and ¹⁹F NMR spectroscopy. Copolymerization of ethylene and norbornene for the metallocene dichloride/MAO and bis-hydrocarbyl complex/borate systems was compared.