The Application Of Salicylaldimine Nickel Catalysts In Ethylene Polymerization

In this dissertation,we designed,synthesized and characterized a series of salicylaldimine ligands,which reacted with the nickel precursors of to obtain a series of salicylaldimine Ni(?)complexes.After characterizing these complexes by nuclear magnetic resonance,elemental analysis,X-ray single crystal diffraction,we studied their properties in ethylene polymerization.1.The steric effect and the electronic effect were considered as the major factors when we designed the new ligands.Compared with the classic salicylaldimine Ni(?)complex,which was reported by Grubbs in 2000,these new complexes are equipped with dibenzhydryl moiety in the ortho-position of the phenyl group.We found that these complexes showed good thermal stability,maintaining high activity at 80 ?.Despite the covalently close proximity of the electron donating or withdrawing substituents to the metal center,the electronic perturbations only exert moderate influence on the ethylene polymerization processes.2.We designed,synthesized and characterized a series of salicylaldimine Ni(?)complexes based on the naphthylamine ligands,and modified the naphthylamine with different aryls.These complexes are highly active at 20 ? in ethylene polymerization,which can generate polyethylene with molecular weight of up to 8.1 × 105.Comparing with the classic salicylaldimine Ni(?)complex,the new complex can increase the polyethylene molecular weight by more than 30 times.