Abstract: Transition metal catalyst based on nickel containing coordinated N and O atoms is a new type of polyolefin catalyst. We modeled a Ni catalyst with [NH=CH－CH=CH－O],and studied the reaction mechanism by the model catalyst using density functional method at the B3LYP/LANL2MB level. The results showed that at first the cationic complex forms a square-planar structure with a vacant site. An ethylene molecule attacks the vacant site, perpendicularly to the [Ni(N=C－C=C－O)] plane, and then it rotates into the plane for an insertion reaction. After insertion reaction, a β- agostic hydrogen bond is formed between Ni and Cβ－H7 so as to assist the regeneracy of a new vacant site and to realize the chain propagation.

Key words: Nickel catalysts, Ethylene polymerization, Density functional method (DFT)