Some silyl and germyl compounds of six-co-ordinated rhodium(III) carbonyl halides

Abstract

Reaction between trans-[Rh(CO)Cl(PEt₃)₂](1) and MH₃Cl (M = Si or Ge) at low temperatures gives equimoler adducts characterised by ¹H and ³¹P n.m.r. spectra as [RhH(CO)Cl(PEt₃)₂(MH₂Cl)] with mutually trans phosphine ligands and M trans to H. Similar reactions occur between trans-[Rh(CO)I(PEt₃)₂](2) and MH₃I. Some of the adducts have been isolated by evaporating solvent at low temperature. Both (1) and (2) give similar adducts with MH₄, MH₃Me, SiH₃CH₂CHCH₂, and SiH₂MeX (X = Cl or I); these dissociate reversibly between 200 K and 280 K, and thermodynamic parameters for dissociation of some of them have been determined from the n.m.r. spectra. Dissociation of the adducts of (2) with organosilanes and with methylgermane is fast on the n.m.r. time-scale, whereas dissociation of the adducts of (1) is slow. The reaction between (1) and MH₃I gives adducts with Cl bound to M and I bound to Rh as the thermodynamically stable products; no halogen exchange was observed in the reaction between (2) and MH₃Cl.