Pyridinethiol-Assisted Dissolution of Elemental Gold in Organic Solutions.

Authors :: Räisänen M
Heliövaara E
Al-Qaisi F
Muuronen M
Eronen A
Liljeqvist H
Nieger M
Kemell M
Moslova K
Hämäläinen J
Lagerblom K
Repo T
Source :: Angewandte Chemie (International ed. in English) [Angew Chem Int Ed Engl] 2018 Dec 21; Vol. 57 (52), pp. 17104-17109. Date of Electronic Publication: 2018 Nov 27.
Publication Year :: 2018
Abstract: Dissolution of elemental gold in organic solutions is a contemporary approach to lower the environmental burden associated with gold recycling. Herein, we describe fundamental studies on a highly efficient method for the dissolution of elemental Au that is based on DMF solutions containing pyridine-4-thiol (4-PSH) as a reactive ligand and hydrogen peroxide as an oxidant. Dissolution of Au proceeds through several elementary steps: isomerization of 4-PSH to pyridine-4-thione (4-PS), coordination with Au <superscript>0</superscript> , and then oxidation of the Au <superscript>0</superscript> thione species to Au <superscript>I</superscript> simultaneously with oxidation of free pyridine thione to elemental sulfur and further to sulfuric acid. The final dissolution product is a Au <superscript>I</superscript> complex bearing two 4-PS ligands and SO <subscript>4</subscript> <superscript>2-</superscript> as a counterion. The ligand is crucial as it assists the oxidation process and stabilizes and solubilizes the formed Au cations.<br /> (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)