Synthesis, properties and structures of complexes of platinum metal halides and Group 11 metals with two distibinomethane ligands, R2SbCH2SbR2 (R = Me or Ph)

The reaction of [Ru(dmf)(6)][CF3SO3](3), LiX and Ph2SbCH2SbPh2 (dpsm) yielded trans-[RuX2(eta(1)-dpsm)(4)] (X = Cl or Br) or [RuI2(eta(1)-dpsm)(2)(eta(2)-dpsm)]. The latter was shown by an X-ray study to contain two monodentate and one chelating dpsm ligands and is the first example with any metal of a distibinomethane acting as a chelate to be authenticated crystallographically. The chelate ring is highly strained as shown by the Sb-Ru-Sb angle (74.3 degrees) and the longer Ru-Sb distances than in the eta(1)-ligands. Corresponding reactions of trans-[OsX2(dmso)(4)] and dpsm produced trans-[OsCl2(eta(1)-dpsm)(4)] and [OsBr2(eta(1)-dpsm)(2)(eta(2)-dpsm)] identified spectroscopically. The reactions of RhX3 (X = Cl, Br or I) with dpsm afford [RhX3(dpsm)(2)] which on the basis of NMR spectroscopic data contain one chelating and one monodentate dpsm ligand. Palladium(II) and platinum(II) halides form both 1 : 1 and 1 : 2 complexes with dpsm. The former are dimeric and crystal structures of [M2X4(dpsm)(2)] (M = Pt, X = Cl or Br; M = Pd, X = Br) revealed a distibine bridged structure with square-planar MX2Sb2 metal centres, one with a cis geometry, the other trans. The structures cis,trans-[X2M(mu-dpsm)(2)MX2] are the first examples of this geometry to be established crystallographically. In contrast [I2M(mu-dpsm)(2)MI2] are assigned as trans,trans isomers on the basis of spectroscopic data. Multinuclear NMR studies show that [PtX2(dpsm)(2)] (X = Cl or Br) contain eta(1)-dpsm and are a mixture of cis and trans isomers in solution, but the [PtI2(dpsm)(2)] contains only a single form, probably the trans isomer. The [PdX2(dpsm)(2)] have also been characterised and for X = Cl shown to undergo facile fragmentation in solution to form trans,trans-[Pd2Cl2(sigma-Ph)(2)(dpsm)(2)]. The complexes [M(L-L)(2)]Y (M = Cu, Ag or Au; Y = BF4 or PF6; L-L = dpsm or Me2SbCH2SbMe2) and [Rh2Cl2(CO)(2)(mu-L-L)(2)] have also been prepared. All complexes have been characterised by analysis, IR, UV-VIS, multinuclear NMR (H-1, C-13-{H-1}, Pt-195, Cu-63 and Ag-109) spectroscopies as appropriate. Comparisons are drawn between the various co-ordination modes of the distibines and those of Ph2PCH2PPh2 and related ligands.