M.C. White, Chem 153 EMPolymerization-301 Week of november 18. 2002 Cationic metallocene catalysts First preformed and spectroscopically characterized cationic complex capable of ethylene polymerization. This work supports the proposal that cationic Zr and Ti complexes formed upon olefin inding are the active polymerization catalysts. The low polymerization activity was attributed to the coordinated THF which competes with ethylene for binding -BPh CH3 AgBPhg(l eq) THE H3 Jordan JACS 1986(108)7410 First well-characterized cationic zirconocene catalyst capable of propylene polymerization at high rates. H3C-B(C6 F5)3 B(C6F5)(1 eq). Marks JACS 1991(113)3623M.C. White, Chem 153 EM Polymerization -301- Week of November 18, 2002 Cationic metallocene catalysts ZrI V CH3 CH3 AgBPh4 (1 eq) THF ZrIV CH3 O BPh4 First preformed and spectroscopically characterized cationic complex capable of ethylene polymerization. This work supports the proposal that cationic Zr and Ti complexes formed upon olefin binding are the active polymerization catalysts.The low polymerization activity was attributed to the coordinated THF which competes with ethylene for binding. Jordan JACS 1986 (108) 7410. First well-characterized cationic zirconocene catalyst capable of propylene polymerization at high rates. ZrIV CH3 CH3 B(C6F5)3 (1 eq) C6H6 ZrI V CH3 H3C B(C6F5)3 Marks JACS 1991 (113) 3623