Structural and Spectroscopic Characterisation of Linearly Coordinated Gold(I) Tribenzylphosphine Complexes

Abstract

The 1:1 tribenzylphosphane (PBn3) complexes of gold(I)[(Bn3P)AuX] (X = Cl and Br) have been synthesised, and their structures were determined by single-crystal X-ray crystallography. The compounds are isomorphous, neutral molecules with linearly coordinated P-Au-X arrays. Each structure contains three independent [(Bn3P)AuX] entities lying on the three threefold axes of space group P3c1. The mean bond lengths are Au-Cl 2.302(8), Au-P 2.227(11) Šfor the chloride and Au-Br 2.404(10), Au-P 2.229(4) Šfor the bromide. These contrast with the 1:1 adducts previously reported for copper(I), which take the form [Cu(PBn3)2][CuX2]. The 1:2 AuX:PBn3 compounds that have been synthesised are formulated as [Au(PBn3)2]X箈2O (X = Cl, n = 1 or 2; X = I and BF4, n = 0). Single-crystal X-ray structures show that linearly two-coordinate centrosymmetric [Au(PBn3)2]+ arrays are found in [Au(PBn3)2]Cl爲O and [Au(PBn3)2]BF4 with Au-P bond lengths of 2.2988(7) and 2.3016(7) Šfor the chloride and 2.2975(7) Šfor the tetrafluoroborate. (AuX) bands in the far-IR spectra of [(Bn3P)AuX] are assigned at 320 and 227 cm-1 for X = Cl and X = Br, respectively. The 31P CP MAS NMR spectra of [(Bn3P)AuX] (X = Cl, Br) and [Au(PBn3)2]X (X = Cl爲O, Cl粈2O, I, BF4) are reported, and the observation of 2J(PP) coupling in the spectrum of [Au(PBn3)2]Cl粈2O is consistent with the presence in this complex of noncentrosymmetric cations in which the two phosphorus atoms are inequivalent.