Synthesis and Binding Studies of a Novel Highly Selective Ag(I) Ligand

Ligands bearing S- and N- donors are an important class of extractants with demonstrated efficiency and selectivity for Ag⁺ extraction over metals with similar chemistries. However, the synthesis of some of these ligands can be complicated and low yielding. Here, we report the synthesis of a novel ligand - N-(2-((4-vinylbenzyl)thio)ethyl)acetamide, over two simple steps and in a good yield. The extractant was observed to demonstrate excellent selectivity for Ag⁺, extracting only Ag⁺ from an aqueous solution also containing Cu²⁺ and Pb²⁺. Moderate extraction efficiencies of 36 % for Ag⁺ and 0% each for Cu²⁺ and Pb²⁺ were observed. From mass spectrometry and proton NMR titration data, the extractant was found to form both the 1:1 and 1:2 (Ag⁺:ligand) complexes with Ag⁺ indicating that ligand forms bent linear and tetrahedral coordination complexes with Ag⁺. Overall, the results indicate that the novel amide-based ligand is highly selective for Ag⁺ removal from aqueous solutions containing Cu²⁺ and Pb²⁺. These results indicate the ligand could be easily synthesized and applied for selective silver recovery from low grade ores.