ELECTRON-LIGAND INTERCHANGE REACTIONS BETWEEN PALLADIUM(II) COMPLEXESAND MERCURY AND SINGLE-CRYSTAL X-RAY CHARACTERIZATION OF THE D(10)-D(10) BINUCLEAR [HG-2(DPPM)(2)CL-3]CL COMPLEX

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 pr oduced 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) bi nuclear complexes using the Hg2+ cations. One of the investigated comp lexes has been characterized by X-ray crystallography, yielding d(Hg-2 ) = 3.343(3) Angstrom, and very weak Hg...Hg interactions are witnesse d 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 s mall (similar to 0.07 mdyn(-1)).