Novel [Ru(L)(Tpms)]Cl and [Ru(L)(TpmsPh)]Cl complexes (L = p-cymene, benzene, or hexamethylbenzene, Tpms = tris(pyrazolyl)methanesulfonate, TpmsPh = tris(3-phenylpyrazolyl)methanesulfonate) have been prepared by reaction of [Ru(L)(μ-Cl) 2 ] 2 with Li[Tpms] and Li[TpmsPh], respectively. [Ru(p-cymene)(Tpms)]BF 4 has been synthesized through a metathetic reaction of [Ru(p-cymene)(Tpms)]Cl with AgBF 4 . [RuCl(cod)(Tpms)] (cod = 1,5-cyclooctadiene) and [RuCl(cod)(TpmsPh)] are also reported, being obtained by reaction of [RuCl 2 (cod)(MeCN) 2 ] with Li[Tpms] and Li[TpmsPh], respectively. The structures of the complexes and the coordination modes of the ligands have been established by IR, NMR, and single-crystal X-ray diffraction (for [RuL(Tpms)]X (L = p-cymene or HMB, X = Cl; L = p-cymene, X = BF 4 )) studies. Electrochemical studies showed that each complex undergoes a single-electron RuII → RuIII oxidation at a potential measured by cyclic voltammetry, allowing to compare the electron-donor characters of the tris(pyrazolyl)methanesulfonate and arene ligands, and to estimate, for the first time, the values of the Lever E L ligand parameter for TmpsPh, HMB, and cod.