13C, 15N and 31P NMR study of the disproportionation of cyanogold(I) complexes: [R 3PAu 13C 15N

Abstract

The disproportionation of cyanogold(I) complexes of general formula [R 3PAu 13C 15N] forming [(R 3P) 2Au] + and [Au( 13C 15N) 2] − ions has been investigated using 13C, 15N and 31P NMR spectroscopy for a series of phosphines with R=cyclohexyl, i-propyl, Et, Me, cyclohexyl/diphenyl, o-tolyl, p-tolyl, m-tolyl, p-tolyl/diphenyl, allyl/diphenyl, phenyl, tri(cyanoethyl) CEP, and 1-naphthyl. The 13C NMR of the 13C 15N group in these complexes exhibited two distinct resonances, one due 13C in the starting [R 3PAu 13C 15N] complex and the second in the [Au( 13C 15N) 2] − anion. The 31P NMR spectra revealed two 31P resonances due to [R 3PAu 13C 15N] complex, and the [(R 3P) 2Au] + cation. The 15N NMR revealed only an averaged resonance due to [R 3PAu 13C 15N] and [Au( 13C 15N) 2] − anion, except in the cases of [Me 3PAu 13C 15N] and [Et 3PAu 13C 15N] where two resonances were observed. The coupling constants, 1J( 13C– 15N), 2J( 31P– 13C) and 3J( 31P– 15N) were obtained for all complexes and the free energies of activation for ligand disproportionation were determined using 31P–{ 1H} NMR band shape analysis.