Highly active and stereospecific polymerization of 1,3-butadiene catalyzed by bis{[2-(4,5-diphenylimidazolyl)phenylimino]phenolate}cobalt(II) complexes

A series of bis{[2-(4,5-diphenylimidazolyl)phenylimino]phenolate}cobalt(II) complexes ( C1 – C4 ) has been synthesized and characterized. Single-crystal X-ray analysis demonstrated that the cobalt center was coordinated by two [NNO – ] ligands and adopted a slightly distorted octahedronal geometry. The type of cocatalyst had a remarkable influence on the catalytic properties and ethylaluminum sesquichloride (EASC) was proved to be more efficient for the polymerization of 1,3-butadiene to produce higher conversion of butadiene and cis -1,4 content of polybutadienes . On activation with EASC, all the cobalt complexes displayed high catalytic activity for the polymerization of 1,3-butadiene. The microstructure determined by FT-IR and NMR spectra demonstrated that high cis -1,4 contents in the resulting polymers were obtained. The conversion of butadiene , microstructure, molecular weight and molecular weight distribution of polybutadienes were influenced by the reaction parameters and ligand structure .