A series of cobalt dicholoride complexes (1~4) bearing[2-(4

5-diphenylimidazolyl)phenylimino]phenol ligands ([N^N^O] tridentate ligands) have been synthesized and characterized by FTIR spectra and elemental analysis.These cobalt complexes 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 proven to be the best cocatalyst

yielding higher conversion of butadiene and 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 displayed high catalytic activity for the polymerization of 1

3-butadiene

and high cis-1

4 contents in the resulting polymers were obtained.