Homogeneous Hydrogenation of Nitriles Catalyzed by Molybdenum and Tungsten Amides

Low-valent molybdenum and tungsten amides M(NO)(CO)(PNP) {M = Mo, 1a; W, 1b; PNP = N(CH2CH2PiPr2)2} were found to be active catalysts for the hydrogenation of various nitriles to the corresponding imines, primary amines, and N-substituted imines with high selectivity for the latter type of product. A wide range of p- and m-substituted aromatic nitriles—p-methyl, p-methoxy, p-bromobenzonitriles; 3-trifluoromethylbenzonitrile, m- and p-disubstituted benzonitrile; the heterocyclic 2-thiophencarbonitrile; and the aliphatic nitriles cyclohexylcarbonitrile and benzylcyanide—could be hydrogenated at 140 °C and 60 bar H2 in THF with high yields. TOFs were found to be between 0.4 and 36 h–1.