Bis(benzimidazolyl, benzothiazolyl, and benzoxazolyl)benzene complexes as catalysts for ethylene polymerization

Abstract

A series of 36 complexes of 1,2-bis(benzimidazolyl, benzothiazolyl and benzoxazolyl)benzene compounds with Ti(IV), Zr(IV) and V(III) were synthesized and characterized. After activation with methylaluminoxane (MAO), they showed variable activities towards ethylene polymerization. Parameters like the steric conditions and the number and nature of the hetero atoms at the precatalyst molecule, the concentration of the cocatalyst MAO, the nature of the transition metal and the reaction temperature have a strong influence on the performance of the corresponding catalysts. The polymerization activity of the catalyst system [1,2-bis(benzimidazolyl)benzene zirconium tetrachloride] 20/MAO was investigated under various polymerization conditions. Studies of structure–property relationships allowed the optimization of catalysts. Bimodal or multimodal resins indicate the existence of more than one active site in the polymerization reaction in one type of homogeneous catalyst.