New ansa-metallocenes of the Group 4 transition metals as homogeneous catalysts for the polymerization of propene and styrene

The ansa-bridged metallocenes [M{CR2(η-C5H4)(η-C9H6)}Cl2], [M = Ti, Zr or Hf; CR2= CMe2, CPh2 or C(CH2)5] have been prepared. The crystal structure of [Zr{CMe2(η-C5H4)(η-C9H6)}Cl2] has been determined. Some of these new ansa-metallocenes in the presence of methylaluminoxane (AlMeO)n give homogeneous catalysts, which for the polymerization of propene yield isotactic rich polypropene and of styrene yield syndiotactic polystyrene.