Unprecedented electron-ligand interchange reactions are reported. For the first time mercury reduces Pd-II complexes (Pd(dppm)X(2) (X = Cl, Br)) to Pd(0) presumably via an inner-sphere mechanism, and in return, the oxidized metal (Hg2+) coordinates to the released ligands. The produced new complexes [Hg-2(dppm)(2)(mu-X)(X)(2)]X (X = Cl, Br) belong to a large d(10)-d(10) "M(2)(diphos)(2)" family (M = Pd-0, Pt-0, Ag-I, Au-I, diphos = dppm or dmpm) and are the first examples of d(10) binuclear complexes using the Hg2+ cations. One of the investigated complexes has been characterized by X-ray crystallography, yielding d(Hg-2) = 3.343(3) Angstrom, and very weak Hg...Hg interactions are witnessed by the Raman-active low frequency nu(Hg-2) (48 and 46 cm(-1) for X = Cl and Br, respectively). The estimated Hg-2 force constant is very small (similar to 0.07 mdyn(-1)).