The Hydrogenation Problem in Cobalt‐based Catalytic Hydroaminomethylation

The hydroaminomethylation (HAM) reaction converts alkenes into N ‐alkylated amines and has been well studied for rhodium‐ and ruthenium‐based catalytic systems. Cobalt‐based catalytic systems are able to perform the essential hydroformylation reaction, but are also known to form very active hydrogenation catalysts, therefore we examined such a system for its potential use in the HAM reaction. Thus, we have quantum‐chemically explored the hydrogenation activity of [HCo(CO) 3 ] in model reactions with ethene, methyleneamine, formaldehyde, and vinylamine using dispersion‐corrected relativistic density functional theory at ZORA‐BLYP‐D3(BJ)/TZ2P. Our computations reveal essentially identical overall barriers for the catalytic hydrogenation of ethene, formaldehyde, and vinylamine. This strongly suggests that a cobalt‐based catalytic system will lack hydrogenation selectivity in experimental HAM reactions. Our HAM experiments with a cobalt‐based catalytic system (consisting of Co 2 (CO) 8 as cobalt source and P( n ‐Bu) 3 as ligand) resulted in the formation of the desired N ‐alkylated amine. However, significant amounts of hydrogenated starting material as well as alcohol (hydrogenated aldehyde) were always formed. The use of cobalt‐based catalysts in the HAM reaction to selectively form N ‐alkylated amines seems therefore not feasible. This confirms our computational prediction and highlights the usefulness of state‐of‐the‐art DFT computations for guiding future experiments.