13 C NMR Studies of the Redox and Exchange Reactions of Gold(I) Thiomalate with Diselenides

Exchange reactions of gold(I) thiomalate (AuStm) n with two diselenides (RSe-SeR), selenocystine and selenocystamine have been studied in D 2 O by 13 C NMR spectroscopy. Upon interaction of diselenides with (AuStm) n , the Se-Se bond is broken, resulting in the formation of RSe-Stm and (AuSeR) n species. RSe-Stm on further decomposition leads to the formation of thiomalic disufide (Stm) 2 . The second order rate constant was determined for the decomposition of RSe-Stm species and is found to be 3.21 2 10 m 4 l mol m 1 s m 1 . The intensity of thiomalic disulfide resonances increases, while the intensity of RSe-Stm resonances decreases with time. The end result of both reactions is the formation of (Stm) 2 and the deposition of metallic gold and brown ppts. In both cases exchange takes place immediately, however, the overall reaction of (AuStm) n with selenocystamine was faster than with selenocystine.