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

Abstract

The reaction of [Ru(dmf)6][CF3SO3]3, LiX and Ph2SbCH2SbPh2 (dpsm) yielded trans-[RuX2(η1-dpsm)4] (X = Cl or Br) or [RuI2(η1-dpsm)2(η2-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°) and the longer Ru–Sb distances than in the η1-ligands. Corresponding reactions of trans-[OsX2(dmso)4] and dpsm produced trans-[OsCl2(η1-dpsm)4] and [OsBr2(η1-dpsm)2(η2-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(μ-dpsm)2MX2] are the first examples of this geometry to be established crystallographically. In contrast [I2M(μ-dpsm)2MI2] 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 η1-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(σ-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(μ-L–L)2] have also been prepared. All complexes have been characterised by analysis, IR, UV-VIS, multinuclear NMR (1H, 13C-{1H}, 195Pt, 63Cu and 109Ag) spectroscopies as appropriate. Comparisons are drawn between the various co-ordination modes of the distibines and those of Ph2PCH2PPh2 and related ligands.