The electronic and solvation structures of the metal complexes in aqueous solutions, [Ru(NH3)(6)](2+) and [Ru(NH3)(6)](3+), which are key species in electron-transfer reactions, are studied by using RISM-SCF method. We have found that the effective charge on the ruthenium ion does not change so much on the process of oxidation, and the electron is lost mainly from the ligand groups. The electrical potential fluctuations around these complexes are nicely described within a linear-response regime, though some nonlinear effect is observed.