Novel C1 symmetric zirconocenes containing substituted indenyl moieties for the stereoregular polymerization of propylene

The synthesis and polymerization behavior of four new asymmetric ansa-metallocenes containing a fluorenyl moiety and a substituted indenyl moiety is reported. The zirconocenes diphenylsilylene-(η5-9-fluorenyl)-[η5-1-(3-t-butyl)indenyl]-zirconium dichloride (4), dimethylsilylene-(η5-9-fluorenyl)-[η5-1-(3-t-butyl)indenyl]-zirconium dichloride (5), ethylene-1-(η5-9-fluorenyl)-2-[η5-1-(3-t-butyl)indenyl]-zirconium dichloride (6), and diphenylsilylene-(η5-9-fluorenyl)-[η5-1-(2-methyl-4-phenyl)indenyl]-zirconium dichloride (8) were all found to be highly active for the polymerization of both ethylene and propylene when activated with excess methylaluminoxane. Compound 8 was found to produce highly isotactic polypropylene with an [mmmm] value of 83%.