Selective Hydration of Nitriles to Corresponding Amides in Air with Rh(I)-N-Heterocyclic Complex Catalysts

A new synthetic method for obtaining [RhCl(cod)(NHC)] complexes (1-4) (cod = eta(4)-1,5-cyclooctadiene, NHC = N-heterocyclic carbene: IMes, SIMes, IPr, and SIPr, respectively) is reported together with the catalytic properties of 1-4 in nitrile hydration. In addition to the characterization of 1-4 in solution by C-13 NMR spectroscopy, the structures of complexes 3, and 4 have been established also in the solid state with single-crystal X-ray diffraction analysis. The Rh(I)-NHC complexes displayed excellent catalytic activity in hydration of aromatic nitriles (up to TOF = 276 h(-1)) in water/2-propanol (1/1 v/v) mixtures in air.