ansa-Metallocene derivatives XXXII. Zirconocene complexes with a spirosilane bridge: Syntheses, crystal structures and properties as olefin polymerization catalysts

Article abstract of DOI:10.1016/0022-328X(95)06073-6

Chiral ansa-zirconocene complexes with a trimethylene link between the Si bridge atom and an α-position of each C₅ ring ligand were prepared; two representatives, with i-propyl and t-butyl groups as β-substituents, were structurally characterized. The properties of these complexes with respect to MAO-activated propene polymerization were studied in comparison with those of their Me₂Si-bridged analogs. The t-butyl-substituted spirosilane complex gives a polymer with relatively high content of 3,1-insertions. These increased regioirregularities appear to be associated with decreased coordination gap aperture and increased lateral extension angles of the spirosilane-bridged zirconocene complexes; this notion is supported by a molecular-mechanics analysis of alternative olefin-insertion transition states.