Synthesis of cationic cobalt(II) complexes and their efficiency as catalysts for the polymerization of 1,3-butadiene

Abstract1 1,10-phenanthroline; Bipy, bipyridine; BZI, benzimidazole; Im, imidazole; EASC, ethylaluminum sesquichloride; GPC, gel permeation chromatography. es of novel cationic cobalt(II) compounds accompanied by various counter ions ([BF4]−, [PF6]−, [SbF6]−) and N-bearing ligands (1,10-phenanthroline, bipyridine, benzimidazole, and imidazole) were synthesized. Neutral compounds, CoCl2-nLigands, were prepared as reference compounds. All the compounds were characterized using IR spectral analysis and elemental analysis and some of the compounds were further characterized by single-crystal X-ray diffraction analysis. The synthesized compounds were evaluated as precursors for butadiene polymerization in conjunction with ethylaluminum sesquichloride as a cocatalyst, and the polymerization mechanism was proposed to involve anionic coordination polymerization. The active centers of the catalysts were cationic in nature, and the catalytic activities were affected by the electronegativity of the counter ion.