A Heterogeneous Ruthenium dmso Complex Supported onto Silica Particles as a Recyclable Catalyst for the Efficient Hydration of Nitriles in Aqueous Medium

In the present work, we describe an efficient method for the covalent anchoring of a Ru-dmso complex onto two types of supports: mesoporous silica particles (SP) and silica coated magnetic particles (MSNP). First, we have prepared and characterized the molecular complexes containing the bidentate pyridylpyrazole ligands pypz-Me and pypz-CH2COOEt, with the formula [(RuCl2)-Cl-II(pypz-R)(dmso)(2)] (R = Me, 1; CH2COOEt, 2). Complex 2 was anchored onto the silica supports, yielding the heterogeneous systems SP@2 and MSNP@2 which were fully characterized by IR, UV-vis, SEM, TEM, TGA, and XPS techniques. Hydration of representative nitriles has been tested with the molecular complexes and their SP@2 and MSNP@2 heterogeneous counterparts, in aqueous medium under neutral conditions. The heterogeneous catalysts display high yields and excellent selectivity values. Both systems can be reused throughout several cycles for benzonitrile and acrylonitrile substrates, without any significant loss in reactivity. The MSNP@2 material can be easily recovered by a magnet, facilitating its reusability.