Gold and silver cations in the "Procrustean bed" of the bis[2-(diphenylphosphino)phenyl]phenylphosphine ligand. Observations and conclusions

Reaction of [Au(Me2S)Cl] or AgCl with equimolar quantities of bis[2-(diphen ylphosphino)phenyl]phenylphosphine (TP) gave isomorphous crystalline 1 : 1 complexes with a greatly distorted tetrahedral environment for Au-I and Ag- I. The large differences in the metal-to-phosphorus interactions are also o bvious from the NMR parameters in solution. The complex [Au(TP)Cl] is conve rted into the tetrafluoroborate [Au-2(TP)(2)][BF4](2) when treated with AgB F4. This ionic compound has a dinuclear dication with grossly different env ironments for the two gold atoms: one is trigonally planar three-co-ordinat ed with a short intramolecular Au Au bond [2.8776(4) Angstrom]. The second gold atom is five-co-ordinated with the other gold atom as an equatorial co ntact. By contrast, the dicationic part [Ag-2(TP)(2)](2+) of the product ob tained by reaction of TP with AgBF4 has equivalent silver atoms (related by a center of inversion) which are in a tetrahedral environment including a very short intramolecular Ag ... Ag distance [2.8569(8) Angstrom]. The temp erature dependence of the NMR spectra of [M-2(TP)(2)][BF4](2) (M = Au or Ag ) reflects the fluxional behaviour of these highly strained units in soluti on.