Bis(benzothiazolyl) titanium, zirconium and vanadium complexes as catalysts for ethylene polymerization

Abstract

13 titanium, zirconium and vanadium complexes with 1,1-bis(benzothiazolyl)methane, 1,2-bis(benzothiazolyl)-ethane, 1,2-bis(benzothiazolyl)benzene and 2,6-bis(benzothiazolyl) pyridine ligands were synthesized and characterized. After activation with methylalumoxane (MAO), these complexes proved as good catalysts for ethylene polymerization in spite of the hetero atoms in the catalyst molecules and the oxophilicity of the metals. Structure–property-relationship studies indicated that the bridging unit connecting the two heterocyclic moieties has a strong influence on the performance of the catalysts. Different interactions of the catalyst cation and the bulky MAO anion, due to the various hetero atoms, could be responsible for this behavior. The produced polyethylenes show bimodal or multimodal molecular weight distributions indicating more than one active site in the polymerization process. Therefore such mononuclear catalysts are good candidates for single-reactor bimodal or multimodal polyethylene technology. The polymerization activity of the catalyst system [1,2-bis(benzothiazolyl)benzene zirconium tetrachloride] 13/MAO was investigated under different polymerization conditions.