Issue 23, 2014

Studies on the reactions of [AuCl4] with different nucleophiles in aqueous solution

Abstract

In order to distinguish between the different types of reactions that can occur between Au(III) species and simple nucleophiles, including iodide, bromide, nitrite, thiourea, pyridine and dimethyl sulfoxide, spectrophotometric techniques including stopped-flow and rapid-scan measurements were employed under specific reaction conditions. All experiments were performed in a 0.4 M NaCl aqueous solution to maintain a high chloride concentration and a constant ionic strength. The temperature dependence of the observed rate constants confirmed the associative nature of the ligand substitution reactions. The redox behaviour of the Au(III) species was studied by cyclic voltammetry and confirmed the reversible redox transitions at ca. 0.38 V (SCE, E = 0.1 V s−1). Results obtained during the reaction progress were attributed to the formation of Au0. This oxidation state was observed for the reactions with thiourea, iodide and nitrite, whereas pyridine showed a potential shift only to Au(I) formation, while bromide showed potential shifts typical of ligand substitution reactions. The reaction with dimethyl sulfoxide was studied using 1H NMR and ab initio (RMP2(full)/LANL2DZp) techniques, which revealed why Au(III) does not react with sulfoxide. The results are discussed in terms of the importance of the stability of the Au(III) species in aqueous solutions of the selected salts and bases. In this way, one could differentiate between a possible three-electron inner-sphere redox process and/or a substitution process during the rapid initial step of the reactions.

Graphical abstract: Studies on the reactions of [AuCl4]− with different nucleophiles in aqueous solution

Supplementary files

Article information

Article type
Paper
Submitted
23 Jan 2014
Accepted
26 Mar 2014
First published
23 Apr 2014
This article is Open Access
Creative Commons BY-NC license

Dalton Trans., 2014,43, 8620-8632

Author version available

Studies on the reactions of [AuCl4] with different nucleophiles in aqueous solution

M. D. Đurović, R. Puchta, Ž. D. Bugarčić and R. van Eldik, Dalton Trans., 2014, 43, 8620 DOI: 10.1039/C4DT00247D

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