The weak metal-metal interactions of Pt(II)-Ag(I)/Cu(I) have been investigated by ab initio method at MP2 level through the model complexes [trans-Pt(PH3)(2)(CN)(2)-M(PH3)(2)(+)] (M = Ag, Cu). The calculated interaction energy of 12.9 and 11.5 kcal mol(-1) for [trans-Pt(PH3)(2)(CN)(2)-Ag(PH3)(2)(+)] and [trans-Pt(PH3)(2)(CN)(2)-Cu(PH3)(2)(+)] respectively, are in the middle of the van der Waals force and the strong hydrogen bond. The estimated equilibrium separations between Pt and M, r(eq)(Pt-M) (3.32 Angstrom for M = Ag and 3.23 Angstrom for M = Cu), lie within the region expected for weak metal-metal interaction. The electronic dispersive contributions dominate the weak interaction. (C) 2004 American Institute of Physics.