摘要
水杨醛亚胺— Ni( )催化剂是一类新型烯烃聚合催化剂 ,这类催化剂的主要优势在于它们产生一个中性的活性催化剂中心 ,因而避免了当前均相单中心催化剂所遇到的离子配对问题且不需要助催化剂 .用密度泛函 ( DFT)中的 B3LYP方法和赝势基组 L ANL2 MB对其催化乙烯聚合的反应机理进行了研究 .计算结果表明 ,乙烯的插入是从乙烯配位到缺电子的金属中心开始的 ,形成一个 π-络合物 ,这个络合物通过形成一个四员环的过渡态来支持烯烃插入到 Metal- C键中 ,插入后 ,首先生成一个具有 γ- agostic相互作用的物种 ,再通过键的旋转 ,最终形成具有 β-agostic相互作用的中间体 ,这个中间体为下次乙烯的插入和链的增长形成了一个新的空的配位中心 .
Salicylaldiminato Nickel(Ⅱ) complexes are neutral single component polymerization catalysts. Their advatages are that they produce neutral active sites which reduce the ion-pairing problems encountered in the current catalysts, and do not need cocatalysts. The present DFT study investigates the ethylene polymerization mechanism of these neutral complexes. The result shows that the insertion is initiated by the complexation of incoming ethylene to the electron-deficient metal center into form a π-complex. This complexation assists the insertion of the ethylene into the metal-carbon bond via a four member cyclic transition state. After insertion, a product with γ-agostic interaction is formed. Finally, the product with β-agostic interaction of insertion resembles the starting material in that a new vacant coordination site is available for the next etylene to coordinate and propagate the chain.
出处
《哈尔滨师范大学自然科学学报》
CAS
2003年第3期57-60,共4页
Natural Science Journal of Harbin Normal University
