Group 4 metal (Zr, Ti, Hf) catalysts for olefin polymerization and specifically those based on non-metallocene complexes have continued to be a subject of intense study in homogeneous catalysis. With a view to forming new or improved polyolefinic materials, complexes bearing N-donor anionic ligands such as β-diketiminate, amidinate, guanidinate, amido, imido as well as mixed N-donor ligands including N,C,C-azaallyl and N,O-phenoxy-imine, have been central to many key developments; high catalytic activities for homo- and copolymerization of ethylene have been a highlight of their catalysis. The fine tuning of these nitrogen-containing ligands significantly controls the catalytic performances of their metal catalysts as well as the structural properties of the resulting polymers with high molecular weight or even ultra-high molecular weight materials accessible. In this review the focus is on more recent publications in the field, in which we correlate the influence of ligand structure with the catalytic performance and microstructure of the polyethylenes. Furthermore, we examine the effects of co-catalyst on activity and thermostability of the precatalyst while efforts directed towards the copolymerization of ethylene with 1-hexene are also summarized. Overall, this work presents an overview of current knowledge pertaining to catalyst design and especially with regard to how the modulation of steric and electronic properties impact on the (co)polymerization process.

用于烯烃聚合的第4族金属（Zr，Ti，Hf）催化剂，特别是基于非茂金属络合物的催化剂，一直是均相催化研究的热点。以形成新的或改进的聚烯烃材料，复合物轴承Ñ端供体的阴离子配体，如β -二亚胺基，脒基，胍基，酰胺基，酰亚胺基以及混合ñ端供体配体，包括N，C，C -azaallyl和N， Ø-苯氧基亚胺对许多关键的发展都至关重要；乙烯均聚和共聚的高催化活性一直是其催化的亮点。这些含氮配体的精细调节显着地控制了它们的金属催化剂的催化性能以及所得的具有高分子量或什至是超高分子量材料的聚合物的结构性能。在这篇综述中，重点是该领域的最新出版物，其中我们将配体结构的影响与聚乙烯的催化性能和微观结构相关联。此外，我们研究了助催化剂对预催化剂活性和热稳定性的影响，同时也总结了针对乙烯与1-己烯共聚的努力。总体，