A series of Ru(II) complexes of the ONNS donor ligand mono(4-(4-tolyl)thiosemicarbazone) of 2,6-diacetylpyridine (L2H) synthesized by using three different ruthenium-containing starting materials RuCl3 . xH(2)O, Ru(PPh3)(3)Cl-2, and [Ru(NH3)(5)Cl]Cl-2 are reported. Chemical and electrochemical studies of the complexes [Ru(L-2)(PPh3)(2)]ClO4 (1), [Ru(L-2)(PPh3)(2)]Cl (2), [Ru(L-2)(PPh3)]ClO4 . EtOH (3), [Ru(L-2)(PPh3)(bpy)]ClO4 (4), [Ru(L-2)(PPh3)(ophen)]ClO4 (5), [Ru(L-2)(2)] (6), and [Ru(L-2)(L2H)]Cl (7) have been carried out. The structure of the compound [Ru(L-2)(PPh3)(2)]ClO4 (1) has been determined by single-crystal X-ray diffraction techniques. The crystals are triclinic, space group with a = 12.716(1) Angstrom, b = 13.213(1) Angstrom, c = 15.951(1) Angstrom, alpha = 87.66(1)degrees, beta = 73.81(1)degrees, gamma = 70.93(1)degrees, and Z = 2, where the deprotonated ligand mono(4-(4-tolyl)thiosemicarbazone) of 2,6-diacetylpyridine (L-2) is chelated to the Ru(II) center through the oxygen of the carbonyl group, pyridine ring nitrogen, imine nitrogen, and the thiolate sulfur atoms. Strong coordination of the carbonyl group suggested from its IR spectral characteristics has been confirmed from the appreciable shortening of the Ru-O bond and lengthening of the C=O bond in the structure of 1.