Structural and spectroscopic characterisation of linearly coordinated gold(I) tribenzylphosphane complexes

Article abstract of DOI:10.1002/ejic.200901209

The 1:1 tribenzylphosphane (PBn₃) complexes of gold(I)[(Bn ₃P)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) A for the chloride and Au-Br 2.404(10), Au-P 2.229(4) A for 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·nH₂O (X = Cl, n = 1 or 2; X = I and BF₄, n = O). Single-crystal X-ray structures show that linearly two-coordinate centrosymmetric [Au(PBn₃)₂]⁺ arrays are found in [Au(PBn₃)₂]Cl·H₂O and [Au(PBn ₃)₂]BF₄ with Au-P bond lengths of 2.2988(7) and 2.3016(7) A for the chloride and 2.2975(7) A for the tetrafluoroborate. v(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(PBn ₃)₂]X (X = Cl·H₂O, C1·2H ₂O,1, BF₄) are reported, and the observation of ₂J(PP) coupling in the spectrum of [Au(PBn₃) ₂]Cl· 2H₂O is consistent: with the presence in this complex of noncentrosymmetric cations in which the two phosphorus atoms are inequivalent.