A Cobalt Complex Catalyst for the Linear Dimerization of Butadiene

Abstract In the linear dimerization of butadiene, the mixing order of butadiene and catalyst components, cobalt acetylacetonate and triethylaluminum affects the activity of the catalyst. When cobalt acetylacetonate and triethylaluminum react in the presence of butadiene, the solution possesses marked catalytic activity. In the infrared spectrum of this system, the intensity of the absorption peaks of the CH-(1008 cm−1) and CH2- (908 cm−1) wagging vibrations of butadiene decrease significantly as compared with the case when butadiene is added last. In both cases, the absorption of Co–O (466 cm−1) disappered and that of Al–O (490 cm−1) was found. These results indicate that triethylaluminum reduces cobalt acetylacetonate and coordinates butadiene to cobalt. When butadiene is absent, triethylaluminum and cobalt acetylacetonate react to form a complex to which butadiene coordinate scarcely at all afterwards. The former solution shows a weak paramagnetism (μeff=1.4), while the latter shows a strong paramagnetism (μeff=4.0), From these results, the catalyst of the reaction is considered to be a diamagnetic complex of cobalt coordinated by butadiene.