Ligand scrambling reactions of cyano(thione)gold(I) complexes and determination of their equilibrium constants

Ligand scrambling reactions in cyano(thione)gold(I) complexes ([>C=S-Au-CN]) to form [Au(>C=S) 2 ] + and [Au(CN) 2 ] – species have been investigated for a series of thiones in DMSO using 13 C and 15 N NMR spectroscopy. Rapid approach to equilibrium occurred and resulted in distinct signals for the [>C=S-Au-CN] and [Au(CN) 2 ] – complexes, both in 13 C and 15 N NMR. Equilibrium constants (K eq ) were determined for scrambling of all the complexes by integrating the CN resonances in the 13 C NMR recorded at 298 K. The influence of various factors (initial concentration, ionic strength, temperature, and solvent polarity) on the K eq value was examined for a representative complex (ImtAuCN (Imt = Imidazolidine-2-thione)).Key words: cyanogold(I) complexes, thiones, ligand scrambling, NMR, K eq .