CO2 catalytic hydrogenation to formate was achieved (TONmax =ca. 3800) in the presence of the neutral, halide-free, coordinatively saturated tris(carbonyl) manganese pincer-type complex [Mn(PNP)(CO)3 ], bearing a diarylamido pincer-type PNP ligand, using DBU as base and LiOTf as Lewis acid additive, under mild reaction conditions (60 bar, 80 °C). DFT calculations suggest that the precatalyst activation key step occurs by intermolecular, base assisted dihydrogen heterolytic splitting rather than by the expected ligand-assisted intramolecular MLC-type mechanism.
Keywords: CO2 hydrogenation; Manganese; catalytic mechanisms; formates; pincer complexes.
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