Structural, 197Au Mössbauer and solid state 31P CP/MAS NMR studies on bis (cis-bis(diphenylphosphino)ethylene) gold(i) complexes [Au(dppey)2]X for X = PF6, I

Abstract

¹⁹⁷Au Mössbauer spectra for the d¹⁰gold(I) phosphine complexes, [Au(dppey)₂]X (X = PF₆, I; dppey = (cis-bis(diphenylphosphino)ethylene), and the single crystal X-ray structure and solid state ³¹P CPMAS NMR spectrum of [Au(dppey)₂]I are reported here. In [Au(dppey)₂]I the AuP₄ coordination geometry is distorted from the ∼D₂ symmetry observed for the PF₆⁻ complex with Au–P bond lengths 2.380(2)–2.426(2) Å and inter-ligand P–Au–P angles 110.63(5)–137.71(8)°. Quadrupole splitting parameters derived from the Mössbauer spectra are consistent with the increased distortion of the AuP₄ coordination sphere with values of 1.22 and 1.46 mm s⁻¹ for the PF₆⁻ and I⁻ complexes respectively. In the solid state ³¹P CP MAS NMR spectrum of [Au(dppey)₂]I, signals for each of the four crystallographically independent phosphorus nuclei are observed, with the magnitude of the ¹⁹⁷Au quadrupole coupling being sufficiently large to produce a collapse of ¹J(Au–P) splitting from quartets to doublets. The results highlight the important role played by the counter anion in the determination of the structural and spectroscopic properties of these sterically crowded d¹⁰ complexes.