Syntheses and structures of non-symmetric guanidinato zirconium and hafnium complexes and their catalytic behavior for ethylene polymerization

Equivalent addition reactions of PhN(Li)SiMe3 to nitriles, RCN (R = dimethylamido, 1-piperidino), generated non-symmetric guanidinato lithium [(Et2O)LiN(SiMe3)C(NMe2)N(Ph)]2 (1) or [(THF)LiN(SiMe3)C(NMe2)N(Ph)]2 (2) and [(Et2O)LiN(SiMe3)C(N(CH2)5)N(Ph)]2 (5) which further reacted with zirconium or hafnium tetrachloride to form Zr and Hf guanidinato complexes with the general formula [PhNC(R)NSiMe3]3MCl (R = dimethylamido, M = Zr (3), Hf (4); R = 1-piperidino, M = Zr (6), Hf (7)). Complexes 1–4, 6 and 7 were well characterized by 1H, 13C NMR and microanalysis, the single crystal X-ray diffraction analysis data for complexes 1, 3, 4 and 7 were also provided. Furthermore, complexes 3, 4, 6 and 7 were found to be active for ethylene polymerization. The influences of cocatalyst, pressure, reaction temperature and Al/M ratio on activity were investigated.