Solvent effect on cis-1,4-specific polymerization of 1,3-butadiene with CoCl2(PRPh2)2–EASC catalytic systems

A series of phosphine-containing cobalt complexes [CoCl2(PRPh2)(2), R = Ph (1), Cy (2), Pr-n (3), Et (4), Me (5), H (6)] has been used for the highly active and stereospecific polymerization of 1,3-butadiene upon activation with ethylaluminum sesquichloride (EASC). The high catalytic activities and polybutadienes with high cis-1,4 selectivity were obtained in the solution polymerization in toluene. The conversion of butadiene and the microstructure and molecular weight of the resulting polymers were affected by reaction parameters and the R group on the phosphine ligand. The dispersion medium was also a sensitive factor for the current catalytic systems, influencing the catalytic activity and properties of products. In comparison with the solution polymerization in toluene, the heterogeneous polymerization in isooctane yielded slightly lower catalytic activity, cis-1,4 content and molecular weight under similar reaction conditions.