Iron, Cobalt And Nickel Complexes Bearing Tridentate Ligands:Synthesis And Catalytic Behavior Towards Ethylene Polymerization

This dissertation focuses on designing and synthesis of unsymmetrical bis(imino)pyridylmetal (iron (Ⅱ) and cobalt (Ⅱ)) complexes with bulky substituents as catalysts for polymerization of ethylene. Upon activation with Al-based co-catalysts, their catalytic behaviors were investigated and discussed in detail. In addition, catalytic behaviors of nickel halide complexes bearing2-benzimidazolyl-N-arylquinoline-8-carboxamide derived ligands were also investigated in this dissertation. So four parts are included as follows:Part Ⅰ:The progress of late transition metal catalysts used in oligomerization and/or polymerization of ethylene is summarized, especially for iron and cobalt complexes.Part Ⅱ:A series of unsymmetrical bis(imino)pyridines were synthesized and reacted with FeCl2·4H2O to afford the iron (Ⅱ) dichloride complexes. All new compounds were fully characterized. Upon activation with either MAO or MMAO, all iron pre-catalysts exhibited very high activity in ethylene polymerization with good thermal stability. The resultant polyethylene possessed a narrow PDI consistent with the formation of single-site active species.Part Ⅲ:A series cobalt complexes bearing unsymmetrical bis(imino)pyridines were prepared and characterized. Although the catalytic activity and thermal stability of cobalt complexes were not as good as those of their iron analogs, polyethylenes produced by cobalt complexes possessed higher molecular weights and narrower PDIs. Interestingly, the molecular weights could be controlled by modifying the nature of ligands or by varying the reaction conditions.Part Ⅳ:A series of nickel halide complexes bearing2-benzimidazolyl-N-arylquinoline-8-carboxamide derived ligands have been synthesized and characterized. Upon activation with Et2AlCl, all nickel pre-catalysts exhibited good to high activities for ethylene oligomerization. Furthermore, in the presence of MAO, they were shown to perform with good activities for the vinyl polymerization of norbornene.