Effect of the bridging unit in bis-(benzoxazolyl) titanium, zirconium and vanadium complexes on catalytic ethylene polymerization reactions

A series of 32 complexes of 1,1-bis-(benzoxazolyl)methane, 1,2-bis-(benzoxazolyl) ethane, 1,2-bis-(benzoxazolyl)benzene and 2,6-bis-benzoxazolyl)pyridine compounds with Ti(IV) chloride, Zr(IV) chloride and V(III) chloride was synthesized and characterized. After activation with methylaluminoxane (MAO), these complexes proved as good ethylene polymerization catalysts. Surprisingly the activities of the corresponding catalysts depend considerably on the nature of the bridging unit of the ligand. Structure property relationship studies revealed that titanium complex 16 with a methylene bridge gave the best performance.