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

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).