On Gold(I) Thiomalate Complexes in Aqueous Solution

Certain equilibria involving polymeric gold(I) thiomalate complexes have been studied by spectrophotometry and pH measurements in aqueous solution at 25°С and I = 0.2 M (NaCl). Thiomalate protonation constants H_i–1Tm^3– + H⁺ = HiTm^i–3 have been found to be logK_H1 = 10.23, logK_H2 = 4.51, logK_H3 = 3.01. Efficient functions have been used to allow for multiple protonation of polymeric complexes Au_n Tm_m ^{n-3 m} Equilibrium constants for reactions Au₄Tm₄ ⁸⁻ + Tm^3– = Au₄Tm₅ ¹¹⁻ (logK₄₅ = 10.1 ± 0.5) and 0.25 Au₄Tm₄ ⁸⁻ + Tm^3– = AuTm₂ ⁵⁻ (logK₁₂ = 4.9 ± 0.2) have been determined. Standard potential for AuTm^{2 5−} has been found to be equal to E_1/0 ⁰ =–0.260 ± 0.025 V.