新型镍催化剂催化乙烯聚合的阳离子机理

含氮氧配位原子的镍催化剂是一类新型催化剂.文章以配体为NH=CH－CH=CH－O]的镍催化剂为模型,用密度泛函方法（DFT）在B3LYP/LANL2MB水平上研究了该类乙烯聚合催化的反应机理.计算结果表明,催化的反应过程中,中心原子镍最先形成带空位的四边形阳离子配合物,乙烯以垂直于催化剂平面的方式占据空位,然后旋转到催化剂平面内以利于插入反应的进行；插入反应发生后,在催化剂中Ni和β-C之间形成一种氢桥键,协助新空位的形成,实现链的增长.

Cationic Reaction Mechanism for Ethylene Polymerization of New Nickel Catalysts

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.