Ru(ii)-dmso complexes containing azole-based ligands: synthesis, linkage isomerism and catalytic behaviour

Abstract

The reaction of cis,fac-[RuCl₂(dmso-S)₃(dmso-O)], 1, with different azole (L) ligands leads to new [RuCl₂(L)(dmso-S)₃] compounds (L = CH₃-pz-H, 2; NO₂-pz-H, 3; CF₃-pz-H, 4 and Br-Hind, 5). Complexes 2–5 have been characterized by analytical, spectroscopic and electrochemical techniques as well as by monocrystal X-ray diffraction analysis. Upon oxidation to Ru(III) the complexes undergo linkage isomerization of a S-bound dmso ligand and the corresponding kinetic rates as well as the thermodynamic properties have been determined for compound 2 and also for the previously described [Ru^IICl₂(pypz-H)(dmso-S)₂] (pypz-H = 2-(3-pyrazolyl)pyridine), 6, from cyclic voltammetries performed at different scan rates. The exposure of compound 2 to visible light in acetonitrile produces the substitution of one dmso ligand by a solvent molecule generating a new compound, 2′. The irradiation of solutions of compounds 2 and 6 in chloroform leads in both cases to the substitution of one dmso by a chlorido ligand in parallel to the oxidation of Ru(II) to Ru(III) generating complexes 2′′ and 6′ respectively. The reactivity of compounds 2–6 has been tested with regard to the hydration of nitriles in water as a solvent, displaying in all cases good performance and selectivity for the corresponding amides.