On the Reaction of Gold(III) Complexes with Methionine

The reactions of gold(III) complexes $${\text{AuCl}}_{4}^{ - }$$ , Au(bipy)Cl $$_{2}^{ + }$$ , Au(en) $$_{2}^{{3 + }}$$ , and Au(C9H19N4)2+ with methionine (HMet) were studied in aqueous solutions (pH 2.0 and 7.4; I = 0.2 M (NaCl), CAu = (5–10) × 10–5 mol/L, CHMet < (6–50) × 10–5 mol/L) at 25°C. Methionine reduces gold(III) to gold(I), but the reactions proceed much more slowly (by hundreds of times) than under the action of thiols. The rate of reactions with HMet markedly decreases with increasing denticity of ligands in the gold(III) complex.