Manganese-Catalyzed Sequential Hydrogenation of CO2 to Methanol via Formamide

Mn(I)-PNP pincer catalyzed sequential one-pot homogeneous CO 2 hydrogenation to CH 3 OH by molecular H 2 is demonstrated. The hydrogenation consists of two parts—N-formylation of an amine utilizing CO 2 and H 2, and subsequent formamide reduction to CH 3 OH, regenerating the amine in the process. A reported air-stable and well-defined Mn-PNP pincer complex was found active for the catalysis of both steps. CH 3 OH yields up to 84% and 71% (w.r.t amine) were obtained, when benzylamine and morpholine were used as amines, respectively; and a TON of up to 36 was observed. In our opinion, this study represents an important development in the nascent field of base-metal-catalyzed homogeneous CO 2 hydrogenation to CH 3 OH.