Gold-197 Mössbauer spectra of organogold(I) compounds

Abstract

Gold-197 Mössbauer parameters are reported for the salts Z[AuR₂]{R = C₆F₅, Z =[NBu₄]⁺, [Ag(C₄H₈S)]⁺, [Au(SbPh₃)₄]⁺, or [Au(pdma)₂]⁺[pdma =o-phenylenebis(dimethylarsine)]; R = C₆F₃H₂, Z =[NBu₄]⁺, Ag⁺, or [Ag(C₄H₈S)]⁺}. For salts of the same cation, the isomer shift and quadrupole splitting are both slightly smaller for R = C₆F₅ than for R = C₆F₃H₂, in accord with the electronegativities of the aryl groups. For each anion, the parameters decrease in the order Z =[NBu₄]⁺ > [Ag(C₄H₈S)]⁺ > Ag⁺; this trend probably indicates increasing interionic association. The data for the two gold-containing cations are consistent with four co-ordination; the lower symmetry of [Au(pdma)₂]⁺ is revealed by a small quadrupole splitting. These cations give more intense spectra than the anions, consistent with dependence of the recoil-free fraction on ionic mass.