SYNTHESIS AND CRYSTAL-STRUCTURE OF THE SUBVALENT MERCURY CLUSTER [TRIANGULO-HG-3(MU-DMPM)(4)][O3SCF3](4) (DMPM=ME2PCH2PME2)

The subvalent mercury cluster [triangulo-Hg-3(mu-dmpm)(4)][O3SCF3](4) [dmpm = bis(dimethylphosphino)methane], involving the +4/3 oxidation s tate of mercury, was formed by reaction of [Hg-2](2+) with 2 equivalen ts of dmpm or by reduction of a mixture of [Hg(Me2SO)(6)][O3SCF3](2) a nd dmpm in the molar ratio 2:4 with elemental Hg. The cation consists of a Hg, triangle [Hg-Hg 276.68(14), 280.99(14) and 295,53(14) pm] in which two edges are bridged by one dmpm ligand and the third edge is d oubly bridged by a pair of dmpm ligands. The three Hg atoms and the ph osphorus atoms of the singly bridging dmpm ligands are nearly in a pla ne. The dihedral angles of the Hg, triangle and the mean planes formed by the doubly bridged Hg atoms and the phosphorus atoms of the two br idging dmpm ligands respectively are 61 and 46 degrees. The complex is fluxional on the P-31 NMR time-scale at 81 MHz at ambient temperature due to intramolecular exchange between the two different types of dmp m ligands.