A New Titanium Complex Having Two Phenoxy-Imine Chelate Ligands for Ethylene Polymerization

Abstract

A new titanium complex having two phenoxy-imine chelate ligands, bis[N-(3-tert-butylsalicylidene)anilinato]titanium(IV)dichloride 1, was synthesized and its structure determined by X-ray analysis. Density functional theory (DFT) calculations and X-ray analysis suggest that complex 1, when activated, possesses two available cis-located sites needed for ethylene polymerization. Complex 1/methylaluminoxane (MAO) in toluene or heptane solvent displayed very high ethylene polymerization activities (2 280–4 150 (kg PE)·(mol cat)–1·h–1) with high molecular weight values (M̄v = 288 000–881 000) at 25–75°C under atmospheric pressure. The activity values displayed by complex 1/MAO are some of the highest values exhibited by any titanium complex with no cyclopentadienyl (Cp) ligand(s). Alternatively, complex 1/iBu3Al/Ph3CB(C6F5)4 in toluene solvent displayed high ethylene polymerization activities (190–670 (kg PE)· (mol cat)–1·h–1) with exceptionally high molecular weight values (M̄v = 3 920 000–5 860 000) at 25–75°C under atmospheric pressure. The molecular weight values displayed by complex 1/iBu3Al/Ph3CB(C6F5)4 are some of the largest values displayed by homogeneous olefin polymerization catalysts including the group 4 metallocenes. The high potential of complex 1 for ethylene polymerization has therefore been demonstrated.