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

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 [(RuCl2)-Cl-II(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.