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 [RuCl 2 (η 6 -C 6 Me 6 ){P(NMe 2 ) 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 [RuCl 2 (η 6 -C 6 Me 6 ){P(NMe 2 ) 3 }] in water was evaluated, observing its progressive decomposition into the less-active dimethylamine–ruthenium(II) complex [RuCl 2 (η 6 -C 6 Me 6 )(NHMe 2 )] by hydrolysis of the coordinated P(NMe 2 ) 3 ligand. The X-ray crystal structure determination of the toluene complex [RuCl 2 (η 6 -C 6 H 5 Me){P(NMe 2 ) 3 }] is also included.