Reactions between tetrachlorogold(III) ions and N-cyclohexylthiobenzamide

Abstract

Kinetic and spectroscopic evidence is presented which shows that in aqueous solution tetrachlorogold(III) ions and N-cyclohexylthiobenzamide (S) interact stoicheiometrically to form the 1 : 1 complexes [AuCl₂(OH)(S)]⁰, [AuCl₂(H₂O)(S)]⁺, [AuCl₃(S)]⁰, and [AuCl₅(S)]^2–. The complexes are in rapid equilibrium and their relative concentrations depend upon the free chloride and hydrogen ion concentrations. All the complexes decompose, probably via a slow reaction with water, to give the O-amide and gold sulphide. In this decompostion [AuCl₅(S)]^2– is the most reactive and the addition of chloride ions to a reaction mixture can therefore provide catalysis based on the conversion of a four- to a six-co-ordinated species. A possible explanation is given.