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

A series of bisf[2-(4,5-diphenylimidazolyl)phenyliminolphenolatelcobalt(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. (C) 2015 Elsevier BY. All rights reserved.