STRUCTURE OF POLYMERIC ANTIMONY SILVER(I) (+)-TARTRATE

The low-temperature (163 K) structure of the silver(l) complex with antimony(lll) (+)-tartrate has been determined by X-ray methods and refined to a residual R of 0.027 for 2926 observed reflections. Crystals are orthorhombic, space group P2(1)2(1)2(1) with cell dimensions a = 8.942(4), b = 15.272(6), c = 21.552(7) angstrom and Z = 4. The repeating unit is described in terms of an unusual complex tetramer with formula [Ag4Sb4(C4H2O6)4(H2O)4] in which there are four independent and different silver and antimony centres. Two of the four silvers are four-, one is five-, while the other six-co-ordinate [Ag-O range 2.156-2.666(8) angstrom]. One silver has three bonded waters with one of these bridging. Although all four antimony ions are involved in two classical four-co-ordinate [Sb2(C4H8O6)2]2- dimer associations [Sb-O range 1.967-2.381(7) angstrom], these are extended into a complex polymer network structure via the silver ions and the tartrate oxygens. Only three of the tartrate oxygens are not involved in bonding with the metal ions while another silver is bonded to the fourth water.