Arene–Ruthenium(II) Complexes Containing Inexpensive Tris(dimethylamino)phosphine: Highly Efficient Catalysts for the Selective Hydration of Nitriles into Amides

The catalytic hydration of nitriles into amides, in water under neutral conditions, has been studied using a series of arene–ruthenium(II) derivatives containing the commercially available and inexpensive ligand tris(dimethylamino)phosphine. Among them, best results were obtained with the complex [RuCl2(η6-C6Me6){P(NMe2)3}], which selectively provided the desired amides in excellent yields and short times (TOF values up to 11 400 h–1). The process was operative with both aromatic, heteroaromatic, aliphatic, and α,β-unsaturated organonitriles and showed a high functional group tolerance. The stability of [RuCl2(η6-C6Me6){P(NMe2)3}] in water was evaluated, observing its progressive decomposition into the less-active dimethylamine–ruthenium(II) complex [RuCl2(η6-C6Me6)(NHMe2)] by hydrolysis of the coordinated P(NMe2)3 ligand. The X-ray crystal structure determination of the toluene complex [RuCl2(η6-C6H5Me){P(NMe2)3}] is also included.