镍配合物[N,N]NiBr_2的合成及其催化乙烯齐聚的研究

Synthesis of Nickel Complexes NiBr_2 and Their Catalysis for Ethylene Oligomerization

吡啶甲醛类化合物与苯胺类化合物缩合形成有机配体 [N ,N],它与金属镍的卤化物NiBr2 作用可形成稳定的配合物[N ,N]NiBr2 .这种配合物在含铝助催化剂存在下显示出较高的催化乙烯齐聚的活性 ,所得乙烯齐聚物具有较高的支化度和较低的α 烯烃含量 .实验结果表明 ,吡啶环与苯环上的取代基对催化反应的活性具有不同的影响 ,助催化剂的种类及用量、反应溶剂和乙烯压力等对该体系的催化反应活性及产物结构具有直接影响 .研究结果表明 ,通过调节催化聚合反应的工艺条件 ,有可能实现控制聚合产物的分子量和分子量分布 ,以及提高产物中α

Ni-based complexes [N,N] NiBr2, in which [N,N] is a bidentate nitrogen ligand N-(2-pyridylmethylene) phenylamine with different substituents, were synthesized. [N,N] NiBr2, exhibits high activity for ethylene oligomerization in the presence of activator containing aluminum, as long as [N,N] is chosen suitably. The main factor governing the activity and the polymer structure is the steric bulk of [N,N]. For [N,N] NiBr2, larger ortho-substituents on aryl ring of the ligand [N,N] tend to form the higher active site. MAO-activated catalysts showed higher activity than Et2AlCl-activated ones, and the reaction in toluene resulted in much higher activity than that in hexane. The oligomers obtained by this system is characteristic of highly branched structure with low alpha-olefin content. However, it is possible to promote the alpha-olefin content by adjusting the catalytic reaction conditions.