Iodine‐Catalysed Dissolution of Elemental Gold in Ethanol
A. Zupanc, Eeva Heliövaara, Karina Moslova, Aleksi Eronen, Marianna Kemell, Črtomir Podlipnik, Marjan Jereb, Timo Repo
Abstract
Abstract Gold is a scarce element in the Earth's crust but indispensable in modern electronic devices. New, sustainable methods of gold recycling are essential to meet the growing eco‐social demand of gold. Here, we describe a simple, inexpensive, and environmentally benign dissolution of gold under mild conditions. Gold dissolves quantitatively in ethanol using 2‐mercaptobenzimidazole as a ligand in the presence of a catalytic amount of iodine. Mechanistically, the dissolution of gold begins when I 2 oxidizes Au 0 and forms a [Au I I 2 ] − species, which undergoes subsequent ligand‐exchange reactions and forms a stable bis‐ligand Au I complex. H 2 O 2 oxidizes free iodide and regenerated I 2 returns back to the catalytic cycle. Addition of a reductant to the reaction mixture precipitates gold quantitatively and partially regenerates the ligand. We anticipate our work will open a new pathway to more sustainable metal recycling with the utilization of just catalytic amounts of reagents and green solvents.