Water Serving as Cocatalyst for the Highly Efficient Homogeneously Catalyzed Conversion of N2O/H2 Mixtures with Optimized Rhodium NHC Complexes

Nitrous oxide (N2O) is a valuable oxygen/nitrogen transfer reagent but reactions with N2O are challenging due to its inertness. Consequently, it accumulates in the atmosphere, and because it is both an ozone‐depleting reagent and potent green‐house gas, effective mitigation methods become important. This study presents rhodium(I) amido bis(olefin) N‐heterocyclic carbene complexes [Rh(trop2N)(NHC)] as robust homogeneous catalysts for the direct hydrogenation of N2O. Kinetic experiments and DFT calculations show that increasing π‐acidity of the NHC and the presence of water significantly enhance the catalytic efficiency. The rhodium‐amido bond facilitates cooperative H2‐cleavage and oxygen atom transfer from N2O. The catalyst is regenerated with the loss of water from the hydroxide intermediate [Rh(OH)(trop2NH)(NHC)], which forms a dimeric complex with a central bridging hydrated hydroxide ligand [H3O2]−. Water facilitates dinitrogen (N2) loss from an intermediate containing an oxy‐diazene ligand [H–N=N–O]−. The optimized catalyst achieves a TON > 230,000 and TOF > 1,300 h−1.