Mechanism of Sulfur Inversion in Sulfide Complexes of Gold(I) and Gold(III)

Article abstract of DOI:10.1246/bcsj.68.1345

Kinetic parameters for the sulfur inversion in various gold chloride complexes of alkyl benzyl sulfides were measured by the dynamic NMR method in order to obtain conclusive evidence for the inversion mechanism.A feature of kinetic data is that entropies of activation are nearly zero both in the gold (III) and gold(I) complexes, this suggesting that the sulfur inversion takes place via pyramidal inversion mechanism without breakage of the Au-S coordination bonds but not the dissociative mechanism.The negligible solvent effect on the inversion rates in the gold(III) and gold(I) complexes supports this mechanism as well.The barrier to sulfur inversion is higher by 2.9 kcal/mol^-1 in the gold(III) complexes than in the corresponding gold(I) complexes.The formal gold(II) complex exists as 1:1 mixture of gold(I) and gold(III) complexes in solution, each of them showing the dynamic behavior independently.The effect of oxidation state of the central gold atom on the sulfur inversion is discussed on the basis of MO calculation.