Synthesis, properties and structures of complexes of platinum metal halides and Group 11 metals with two distibinomethaneligands, 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.