Arene ruthenium(II) complexes containing bis(pyrazolyl) methane ligands have been prepared by reacting the ligands L' (L' in general; specifically L-1 = H2C(pz)(2), L-2 = H2C(pz(Me2))(2), L-3 = H2C(pz(4Me))(2), L-4 = Me2C(pz)(2) and L-5 = Et2C(pz)(2) where pz = pyrazole) with [(arene)RuCl(mu-Cl)](2) dimers (arene = p-cymene or benzene). When the reaction was carried out in methanol solution, complexes of the type [(arene)Ru(L')Cl]Cl were obtained. When L-1, L-2, L-3, and L-5 ligands reacted with excess [(arene)RuCl(mu-Cl)](2), [(arene)Ru(L')Cl][(arene)RuCl3] species have been obtained, whereas by using the L-4 ligand under the same reaction conditions the unexpected [(p-cymene)Ru(pzH)(2)Cl]Cl complex was recovered. The reaction of 1 equiv of [(p-cymene)Ru(L')Cl]Cl and of [(p-cymene)Ru(pzH)(2)Cl]Cl with 1 equiv of AgX (X = O3SCF3 or BF4) in methanol afforded the complexes [(p-cymene)Ru(L')Cl](O3SCF3) (L' = L-1 or L-2) and [(p-cymene)Ru(pzH)(2)Cl]BF4, respectively. [(p-cymene)Ru(L-1)(H2O)][PF6](2) formed when [(p-cymene)Ru(L-1)Cl]Cl reacts with an excess of AgPF6. The solid-state structures of the three complexes, [(p-cymene)Ru(H2C(pz)(2)}Cl]Cl, [(p-cymene)Ru(H(2)Cpz(4Me))(2)}Cl]Cl, and [(p-cymene)Ru{H2C(pz)(2)]Cl](O3SCF3), were determined by X-ray crystallographic studies. The interionic structure of [(p-cymene)Ru(L-1)Cl](O3SCF3) and [(p-cymene)Ru(L')Cl][(p-cymene)RuCl3] (L' = L-1 or L-2) was investigated through an integrated experimental approach based on NOE and pulsed field gradient spin-echo (PGSE) NMR experiments in CD2Cl2 as a function of the concentration. PGSE NMR measurements indicate the predominance of ion pairs in solution. NOE measurements suggest that (O3SCF3)(-) approaches the cation orienting itself toward the CH2 moiety of the L-1 (H2C(pz)2) ligand as found in the solid state. Selected Ru species have been preliminarily investigated as catalysts toward styrene oxidation by dihydrogen peroxide, [(p-cymene)Ru(L-1)(H2O)][PF6](2) being the most active species.