Gold and silver cations in the “Procrustean Bed” of the bis[2-(diphenylphosphino)phenyl]phenylphosphine ligand. Observations and conclusions†

Abstract

Reaction of [Au(Me₂S)Cl] or AgCl with equimolar quantities of bis[2-(diphenylphosphino)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 obvious from the NMR parameters in solution. The complex [Au(TP)Cl] is converted into the tetrafluoroborate [Au₂(TP)₂][BF₄]₂ when treated with AgBF₄. This ionic compound has a dinuclear dication with grossly different environments for the two gold atoms: one is trigonally planar three-co-ordinated with a short intramolecular Au· · ·Au bond [2.8776(4) Å]. The second gold atom is five-co-ordinated with the other gold atom as an equatorial contact. By contrast, the dicationic part [Ag₂(TP)₂]²⁺ of the product obtained 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) Å]. The temperature dependence of the NMR spectra of [M₂(TP)₂][BF₄]₂ (M = Au or Ag) reflects the fluxional behaviour of these highly strained units in solution.