Computational insights into the catalytic role of the base promoters in ester hydrogenation with homogeneous non-pincer-based Mn-P,N catalyst

The reaction mechanism of ester hydrogenation catalyzed by a bidentate aminophosphine ligated manganese catalyst was studied by DFT calculations. Particular emphasize was placed on the role of the alkoxide base additives. The presence of such basic promoters as KOtBu can improve the catalyst activity by lowering the activation barriers of H2 dissociation as well as the hydrogenation step. The promoting effect of KOtBu on H2 activation is much stronger than that of tert-butoxides with other alkali metals, which is crucial for the catalyst regeneration from the deactivated Mn-alkoxide species in the resting state.