Density functional study on the role of electronic factors in variation of polymerization activity for Ziegler-Natta catalyst

The role of electronic factors in the variation of activity of Ziegler-Natta (ZN) catalysts having chloride, alkoxy and other ligands for ethylene and propylene polymerization has been investigated using density functional calculations at B3LYP/LANL2DZ level. The barriers for olefin insertion into [TiCl2CH3](+) for ethylene and propylene are comparable whereas for catalysts with alkoxy and non-alkoxy ligands having varying heteroatoms, the insertion barriers for propylene are about 3-6 kcal/mol higher than the corresponding ethylene insertion barriers. This supports the experimental observation that the propylene polymerization with ZN catalyst having alkoxy and non-alkoxy ligands has very low catalytic activity as compared to that for ethylene polymerization whereas [TiCl2CH3](+) polymerizes both ethylene and propylene. (C) 2004 Elsevier B.V. All rights reserved.