Abstract
Dissymmetric chelating complexes of Ti, Zr and V with 2-(benzimidazolyl, benzothiazolyl, and benzoxazolyl) pyridine ligands were synthesized and characterized. After activation with methylalumoxane (MAO) in solution, these complexes could be applied as ethylene polymerization catalysts. Their activities depend on the metal and the substituents at the pyridine ring and the heterocycle. Structure-property-relationship studies revealed that the titanium and vanadium catalyst systems showed higher polymerization activities than the zirconium analogues. The benzoxazolyl moiety containing vanadium complex 29, with a methyl substituent in the 6-membered ring in meta position to the nitrogen atom in the 5-membered ring, and an unsubstituted pyridine ring showed the highest activity (1154.8 kg PE/mol cat h). The produced polyethylenes exhibited high molecular weights and broad molecular weight distributions. Obviously different active sites are generated in the course of these polymerization reactions. (C) 2015 Elsevier B.V. All rights reserved.