Solvation effects in S(N)2-type oxidative addition of MeI to PtMe2(NH3)(2) was theoretically investigated with RISM-SCF, which provides both of quantum chemical and statistical mechanical information on solvation system. Though the reaction is very difficult to occur in gas phase because of the high barrier which is induced by dissociation of iodide anion from methyl group, the reaction easily occurs in nitromethane because iodide anion is stabilized by nitromethane solvent. This stabilization mainly arises from the solvation free energy of platinum center and iodide anion. The solvation structure obtained from RISM-SCF provides the reason why this reaction easily occurs in nitromethane. (c) 2008 Elsevier B.V. All rights reserved.