Highly active ethylene polymerization catalysts based on titanium complexes having two phenoxy-imine chelate ligands

Article abstract of DOI:10.1016/S1381-1169(01)00303-X

Five titanium complexes having F(s) or CF₃(s) containing phenoxy-imine chelate ligands were prepared and investigated for their potential as ethylene polymerization catalysts using methylalumoxane (MAO) as a co-catalyst at 25°C under atmospheric pressure. Polymerization results showed that the electrophilicity of the titanium center plays a dominant role in determining activity. These results clearly demonstrate, for the first time, the electron-withdrawing substituent effects on polymerization activity. The complexes possessing plural F(s) or CF₃(s) in the phenoxy-imine ligand displayed very high activities exceeding those for Cp₂TiCl₂ and Cp₂ZrCl₂. The activity, 43,300 kg polyethylene (PE) mol-cat^-1 h^-1, exhibited by the complex having three fluorines in the ligand, represents the highest value reported to date for ethylene polymerization catalysts based on titanium complexes under atmospheric pressure at ambient temperatures.