Group 4 Metal Olefin Polymerization Catalysts Stabilized by Bidentate O,P Ligands

Abstract

A series of bis(phosphanylphenoxide) group 4 metal dichloride complexes has been synthesized via treatment of MCl4(THF)2 (M = Ti, Zr, Hf) with sodium salts of the phosphanylphenols. The complexes bearing diphenylphosphine donors adopt C1-symmetric, all-cis ground-state structures as determined by X-ray crystallography. In solution an O,P ligand exchange process is observed. Eyring analyses indicate a nondissociative process proposed to proceed via a 120° rotation of the P,P,Cl or the O,P,Cl trigonal faces. A zirconium complex containing diisopropylphosphine donors adopts a configurationally rigid trans-P2 geometry. In ethylene polymerization studies (methylaluminoxane (MAO) activation), bis(6-tert-butyl-2-diphenylphosphanylphenoxide) zirconium and hafnium catalysts gave activities up to 49 000 and 2000 g/mmol·h·bar, respectively. Both of these catalysts also afforded efficient catalyzed chain growth using ZnEt2. The zirconium derivative afforded activities up to 13 300 g/mmol·h for propylene polymerizatio...