Highly efficient hydrogenation of carbamates catalyzed by pincer ruthenium complexes

The [fac-PNN]RuH(PPh3)(CO) complex (Ru1) has been identified as a highly efficient catalyst for the hydrogenation of a broad spectrum of arylcarbamates and their derivatives (49 examples). The hydrogenation reaction occurs smoothly via CN bond cleavage, affording the desired amines and alcohols or diols at a low catalyst loading of 0.25 mol% in tert-amyl alcohol. Most importantly, this catalytic system offers a promising route for the sustainable depolymerization and recycling of polyurethanes (PUs). Moreover, a detailed mechanism for the hydrogenation of carbamates has been established through combined DFT calculations and control experiments, which suggests that Ru-hydride pathways involve three cycles, with the rate-determining step most likely being the dissociation of the CN bond in the key intermediate H(CO)NHPh. These results have far-reaching implications for the development of more effective and eco-friendly catalytic systems for carbamate transformation and their potential industrial application on a large scale.