Coupled hydrogenation of alkenes and arenes in the presence of catalytic systems based on cobalt Bis(acetylacetonate) and tributylphosphine

The effect of the composition of the catalytic systems based on Co(acac)₂ and tertiary phosphines on the activity and efficiency of cobalt catalysts in the coupled hydrogenation of alkenes and arenes is reported. The process occurs in the presence of cobalt catalysts formed under the action of both organoaluminum compounds and tert-butoxy derivatives of complex aluminum hydrides. NMR and IR spectroscopic methods show that the interaction of the components of the catalytic systems yields mono- and/or trihydrido cobalt phosphine complexes, whose composition depends on the nature of the reducing agent and gas atmosphere. The homogeneous character of the process is hypothesized. The most probable schemes are proposed for the reaction mechanism, according to which the kinetic coupling of alkene (alkadiene) and arene hydrogenations is due to the fact that the reaction proceeds through a σ-alkyl or σ-alkenyl cobalt complex with two phosphorus-containing ligands.