Carbon Dioxide Hydrogenation to Formate Catalyzed by a Neutral, Coordinatively Saturated Tris-Carbonyl Mn(I)-PNP Pincer-Type Complex.

Abstract

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.