N,N’-bis(2-(benzylthio)ethyl)malonamides: Synthesis, Electronic and Steric effects in Silver(I) Extraction and Silver(I) Binding Studies

Unsubstituted and gem-diethyl substituted malonamide derivatives, bearing benzylthio arms were prepared in moderate to high yields at room temperature. It was observed that electronics effects at the 4-aryl position in the malonamide derivatives had a significant effect on the selectivity, but little effect on silver(I) extraction efficiency measured by liquid-liquid extraction experiments (with the 4-methoxy analogue proving the most selective). Increased steric hindrance near the sulfur donor had a small negative effect on silver(I) extraction efficiency, while hindrance at the methylene centre reduces selectivity. One of the malonamide derivatives prepared was found to bind to silver(I) in a 1:1 fashion suggesting a tetrahedral coordination type.