Synthesis of a dinuclear ansa-zirconocene catalyst having a biphenyl bridge and application to ethene polymerization

A novel dinuclear ansa-zirconocene catalyst (mu-C12H8{[SiPh(Ind)(2)]ZTCl(2)}(2)) (I) was prepared by a Wurtz coupling reaction between two equivalent of bisindenylphenylchlorosilane and one equivalent of 4,4'-dibromobiphenyl in THF at reflux temperature for 12 h, followed by a successive reaction with ZrCl4 . 2THF in THF at -78 degrees C. Polymerization of ethene was conducted in a 300 cm(3) glass reactor equipped with a stirrer at 40, 60, 80 and 100 degrees C using MAO or Ph3C[B(C6F5)(4)] as cocatalyst and toluene as the solvent. The catalyst (I) gave linear polyethene with a broader molecular mass distribution (MMD) in a much higher yield as compared to the corresponding mononuclear catalyst derived from [Ph2Si(Ind)(2)]ZrCl2 (II). The apparent activity increased monotonously from 40 degrees C up to 100 degrees C. The replacement of MAO with Ph3C[B6F5)(4)] gave polyethene with a higher molecular weight. (C) 1998 Elsevier Science B.V.