Organoamido zirconium(iv) and titanium(iv) complexes and their catalysis towards ethylene polymerization

Abstract

The reaction of PhN(Li)SiMe₃ with 2 equiv. of dimethylcyanamide with further addition of 2 equiv. of CpTiCl₃ led via Me₃SiCl elimination to dinuclear titanium(IV) compound 1. The reaction of DippN(Li)SiMe₃ with 1 equiv. of dimethylcyanamide with further addition of 1 equiv. of CpTiCl₃ afforded centrosymmetric dimeric titanium(IV) compound 2 and mononuclear 3 with the elimination of Me₃SiCl. The zirconium(IV) compound 4 was obtained by the addition reaction of PhN(Li)SiMe₃ with 2 equiv. of dimethylcyanamide and metathesis reaction with ZrCl₄. X-ray diffraction studies of 1–4 establish the dinuclear titanium(IV) structure in 1, half-titanocene of 2 and 3, and a propeller-like complex fragment of 4. Complexes 2 and 4 show moderate or high activities in the polymerization of ethylene upon activation with methylaluminoxane (MAO).