The carbonyl ligands in Ru(bpy)(CO)(2)Cl-2 and its methyl-substituted derivatives have been replaced by NO and Cl ligands in HCl/HNO3 solution at 240 degrees C. Ru(4,4'-dmbpy)(CO)(2)Cl-2 forms a dicarboxy-substituted bipyridine nitrosyl complex Ru(dcbpy)Cl-3(NO), whereas 6,6'-dimethyl substitution of the 2,2'-bipyridine ligand leads to the splitting of the parent complex Ru(6,6'-dmbpy)(CO)(2)Cl-2 into the fragments (H3O)(2)[Ru(NO)-Cl-5] and 6,6'-dicarboxy-2,2'-bipyridine hydrochloride. In H2O/HNO3 solution, the metal center is able to coordinate water to gain full octahedral coordination geometry.