Zr(IV) complexes of some heterocyclic ligands: synthesis, characterization, andethylene polymerization activity

Abstract

Thirty-one complexes of bis-(benzimidazole, benzothiazole, and benzoxazole) compounds with Zr(IV) metalcenters were synthesized, characterized, activated with methylaluminoxane (MAO), and then tested for catalytic ethylenepolymerization. The activities of the various catalysts were found to be functions of the heteroatoms in the ligandframeworks and the structure around the active metal center. The highest activity was obtained with38/MAO(424kg E/mol cat. h). The produced polyethylenes showed high molecular weights (41/MAO, 1.9 106g/mol) andbroad molecular weight distributions (38/MAO, Mw= 9.64 105g/mol, PD = 23). This could result from differentinteractions of the MAO counter ion with the heteroatoms of the catalyst ligand generating different active sites.