Synthesis Of Novel Cobalt And Nickel Complexes Bearing [NNO] Ligands And Their Catalytic Properties In Homopolymerization Of Butadiene And Norbornene

In this thesis, a seris of imidazolyl phenylimino phenol ligands ([NNO] tridentate ligands) and their corresponding cobalt and nickel complexes have been designed and synthesized. Their catalytic properties in the polymerization of butadiene and norbornene were also investigated. Three parts are included:Part one:The catalysts used in the polymerization of butadiene and norbornene were summarized in detail, especially new late transition metal catalysts.Part two:A series of [2-(4,5-diphenylimidazolyI)phenylimino]phenol ligands ([NNO] tridentate ligands) and their cobalt complexes (1-4 and la-4a) have been synthesized and characterized by FT-IR spectra and elemental analysis. These cobalt complexes (1-4 and la-4a) were applied in the stereospecific polymerization of 1,3-butadiene under various reaction parameters. The type of cocatalyst, Al/Co molar ratio, reaction temperature and ligand structure of cobalt complexes were investigated in order to verify their influences on the catalytic activity and the properties of resulting polymers. Among the Al-based cocatalysts, ethylaluminum sesquichloride (EASC) was proved to be the best cocatalyst, yielding higher conversion of butadiene and high cis-1,4 content of polybutadienes. The increase of Al/Co molar ratio enhanced the conversion of butadiene and slightly affected the molecular weight and microstructure of polymers. The catalytic systems displayed good thermal stability in the temperature range of 25～90 ℃; however, the higher temperature led to the lower molecular weight and broader molecular weight distribution, and the decrease in the cis-1,4 content and the increase in the trans-1,4 and 1,2 content. Upon activation with EASC, all the cobalt complexes had high catalytic activity for the polymerization of 1,3-butadiene and high cis-1,4 contents in the resulting polymers were obtained. Besides, the catalytic activity and thermal stability of cobalt chloride complexes (1-4) and cobalt acetate complexes (la-4a) were compared.Part three:A series of nickel dicholoride complexes (1b～4b) bearing [2-(4,5-diphenylimidazolyl)phenylimino]phenol ligands ([NNO] tridentate ligands) has been synthesized and characterized by FT-IR spectra and elemental analysis. Upon activation with methylaluminoxane (MAO), all the nickel complexes had high catalytic activities for vinyl polymerization of norbornene and the highest activitiy reached 13.72×106 g(PNB)-mol-1(Ni)·h-1. The effect of the monomer concentration, Al/Ni molar ratio, reaction temperature and ligand structure were also investigated.