Wang Chaoqun, Zhang Yuxing, Mu Hongliang, Jian Zhongbao
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun 130022, China.
Dalton Trans. 2020 Apr 15;49(15):4824-4833. doi: 10.1039/d0dt00505c.
As the analogues of classical α-diimine nickel catalysts, pyridine-imine nickel catalysts are of great interest for olefin polymerization to produce low molecular weight and branched polyethylenes. In this contribution, pyridine-imine nickel complexes Ni1-Ni4 bearing dibenzhydryl- and pentiptycenyl-N-aryl substituents and H- and Me-imine backbones were synthesized and systematically studied for ethylene polymerization. X-ray diffraction studies revealed that Ni1, Ni2 and Ni4 adopted a monoligated/binuclear structure, while Ni3 was found to adopt a monoligated/mononuclear structure, which differed from the bisligated/mononuclear mode reported previously. Upon activation with aluminum reagents such as Et2AlCl, MAO or MMAO, all these nickel complexes displayed very high activities (up to 14 530 kg mol-1 h-1) for ethylene polymerization. Branched (12-69/1000C) polyethylenes with low molecular weights (Mw: 0.7-22.1 kDa) were obtained with internal double bonds as the predominant unsaturated groups. The influences of the catalyst structure, type and amount of cocatalyst, time, temperature, pressure, and polar additive on the catalytic performances were thoroughly investigated.
作为经典α-二亚胺镍催化剂的类似物，吡啶-亚胺镍催化剂对于烯烃聚合以生产低分子量和支化聚乙烯具有极大的吸引力。在本论文中，合成了带有二苯甲基和戊省烯基-N-芳基取代基以及H-和Me-亚胺主链的吡啶-亚胺镍配合物Ni1-Ni4，并对其乙烯聚合性能进行了系统研究。X射线衍射研究表明，Ni1、Ni2和Ni4采用单配位/双核结构，而Ni3则采用单配位/单核结构，这与先前报道的双配位/单核模式不同。在用Et2AlCl、MAO或MMAO等铝试剂活化后，所有这些镍配合物在乙烯聚合反应中均表现出非常高的活性（高达14530 kg mol-1 h-1）。得到了以内部双键为主要不饱和基团的低分子量（Mw：0.7-22.1 kDa）支化聚乙烯（12-69/1000C）。深入研究了催化剂结构、助催化剂类型和用量、时间、温度、压力以及极性添加剂对催化性能的影响。
