Bridged 1,2-azaborolyl zirconium complexes: Heterocyclic analogs of the ansa-zirconocene olefin polymerization catalysts

An efficient synthesis of (η5-1,2-azaborolyl)-zirconium(IV) dichlorides has been developed. The structure of Me2Si-bridged-(1,2-azaborolyl) complexes closely resemble those of the corresponding ansa-zirconocenes. On activation with excess methylaluminoxane both bridged and non-bridged complexes form highly active catalysts for the polymerization of ethylene.