Hydroformylation catalyzed by unmodified cobalt carbonyl under mild conditions

Hydroformylation with unmodified cobalt carbonyl catalyst plays a crucial role in industrial production of surfactants and plasticizers. However, syngas pressures of 100 to 400 bar with reaction temperatures of 100° to 250°C are typically applied. We report here that unmodified cobalt carbonyl is a stable hydroformylation catalyst at 140°C under 30 bar of syngas. The activity was comparable to that of recently reported bisphosphine-coordinated cobalt(II) catalysts, which we could not reproduce under the reported conditions. Kinetic and in situ infrared spectroscopic studies confirmed the stability of the unmodified cobalt tetracarbonyl hydride [HCo(CO)₄]. Branched internal olefins were converted to aldehydes with high regioselectivity under low syngas pressures without phosphorus ligands. Bisphosphines had a small promotional effect on the catalyst at phosphorus-to-cobalt loading ratios below 0.6.