Synthesis of zirconocene amides and ketimides and an investigation into their ethylene polymerization activity

The zirconocene amide [Cp2Zr(Cl)N(CH2Ph)2] (5), and the zirconocene ketimides [Cp2Zr(Cl)NC(But)Ph] (7), and [Cp2Zr(Cl)NC(NMe2)2] (9), have been prepared by the transmetallation reactions between the appropriate lithiated organonitrogen compounds and zirconocene dichloride (2). In addition, their methylated derivatives [Cp2Zr(Me)N(CH2Ph)2] (6), [Cp2Zr(Me)NC(But)Ph] (8), and [Cp2Zr(Me)NC(NMe2)2] (10), have been prepared by the reaction of each of the complexes 5, 7 and 9 with MeLi. Compounds 5 and 7 have been characterized by X-ray crystallography and the structure of the cocrystalline complex [Cp2Zr(Cl)NC(But)Ph]0.4[Cp2Zr(Me)NC(But)Ph]0.6 (14), has similarly been determined. All of the complexes 5–10 are active catalysts for the polymerization of ethylene in the presence of a MAO cocatalyst. In contrast, no polymer was produced using B(C6F5)3 as an activator, indicating that direct alkene insertion into the ZrN bonds does not occur.