In general, α-diimine palladium species are more likely to undergo chain walking than the corresponding nickel species, resulting in more branched and topological polyethylene. Moreover, the ligand steric effects have a significant influence on the chain walking in α-diimine system. In this contribution, a series of acenaphthene-based α-diimine ligands bearing bulky diarylmethyl moieties with various electronic effects and the corresponding Ni(II) and Pd(II) complexes were synthesized and characterized. These Ni(II) complexes exhibit high activities in ethylene polymerization even at 80 °C, generating ultrahigh-molecular-weight polyethylenes with low branching density and high melting temperature. The corresponding palladium complexes display moderate activity, leading to semicrystalline polyethylene with low branching density and high melting temperature. Polar functionalized semicrystalline polyethylene with high melting temperature can also be obtained via copolymerization of ethylene with polar monomers using these palladium complexes. Moreover, the remote nonconjugated electronic substituents exert a great influence on the ethylene (co)polymerization. Most importantly, the chain walking ability of metal species can be controlled by changing the ligand steric environment, and the diarylmethyl substituents can even reverse the chain walking trend of palladium and nickel species.

通常，α-二亚胺钯物种比相应的镍物种更有可能经历链走，从而导致更多的支链和拓扑聚乙烯。而且，配体的空间效应对α-二亚胺系统中的链行走具有显着影响。在这一贡献中，合成并表征了一系列具有大量电子效应的带有庞大的二芳基甲基部分的series基的α-二亚胺配体以及相应的Ni（II）和Pd（II）配合物。这些Ni（II）络合物即使在80°C的乙烯聚合中也具有很高的活性，可生成具有低支链密度和高熔融温度的超高分子量聚乙烯。相应的钯配合物显示中等活性，导致低支化密度和高熔化温度的半结晶聚乙烯。具有高熔融温度的极性官能化的半结晶聚乙烯也可以通过使用这些钯配合物使乙烯与极性单体共聚而获得。而且，远程的非共轭电子取代基对乙烯（共）聚合有很大的影响。最重要的是，可以通过改变配体的空间环境来控制金属物种的链行走能力，二芳基甲基取代基甚至可以逆转钯和镍物种的链行走趋势。远程非共轭电子取代基对乙烯（共）聚合有很大影响。最重要的是，可以通过改变配体的空间环境来控制金属物种的链行走能力，二芳基甲基取代基甚至可以逆转钯和镍物种的链行走趋势。远程非共轭电子取代基对乙烯（共）聚合有很大影响。最重要的是，可以通过改变配体的空间环境来控制金属物种的链行走能力，二芳基甲基取代基甚至可以逆转钯和镍物种的链行走趋势。