Incorporation and deoxygenation of carbon dioxide: A metal‐assisted facile conversion of carbon dioxide and primary amines to isocyanates

Metal N ‐alkylcarbamato complexes [M(O 2 CNHR) n ] (M = Na, n = 1; M = Mn, Co, n = 2) were prepared by treating CO 2 with a primary amine RNH 2 (R = Ph, Cy, Pr) and various complex precursors. For M = Mn or Co and R = Cy, MCl 2 can be used as starting material. These complexes were readily decomposed by acyl halides R′COCl (R′ = Ph, Me), and two reaction pathways were observed. One led to decarboxylation and formation of amides RNHC(O)R′, while the other afforded isocyanate RNCO and carboxylic acid (M = Na) or carboxylic anhydride (M = Mn, Co). Analysis of the reaction products showed that the metal plays a major rǒle in the formation of the isocyanate, intercepting one of the reaction products. A mechanistic rationalization is proposed.