Interaction of Pt(II) and Au(III) with organic disulfides in hydrochloric aqueous solution

Abstract

The interaction of Pt(II) and Au(III) with disulfides (L-cystine, cystamine, DL-homocystine and 3,3'-dithiodipropionic acid) in hydrochloric acid aqueous solutions was studied. In the case of Pt(II), the oxidative addition reaction leads to the formation of the Pt(IV) thiol complex. In the case of Au(III) disulfide binding causes a reduction to Au(0) and oxidation of the disulfide to sulfonic acid. Cyclic voltammetry and different spectroscopic methods were used to study the process. The pattern of influence of the metallic properties for d 8 ions in the direction of the reaction was found.

Platinum(II)‐mediated disulfide/thiolate interconversion in organic disulfides: Density functional theory thermodynamic study

“…Table 3 also shows that the formation of thiol complexes of Pt(IV)-[PtCl 4 (SR) 2 ] via oxidative addition is the most thermodynamically favorable for all ligands: the average value of the equilibrium constant for cystine, cystamine, and homocystine is log K = 13.1. This value disagrees with the experimentally observed value of log K = 3.5 for thiol complexes Pt(IV) [21]. However, the difference between the experimental value of log K = 10 for a binuclear complex and the calculated value of log K = 13.1 for a thiol complex of Pt(IV) is three logarithmic units, which is close to the experimental value of log K = 3.5.…”

“…For the reactions describing the formation of binuclear complexes (Table 3), the solvation of Cl À with three to five molecules of water makes a small impact on the value of stability constant. The experimental estimate of the value of stability constant for binuclear complexes of all ligands is log K ~10 within the accuracy of UV-Vis titration method [21]. This value matches well the average calculated log K value of 9.4 for the binuclear complexes of cystine, cystamine, and homocystine.…”

“…Herein, we report a DFT study of the Pt(II)controlled disulfide bond cleavage of L-cystine (H 4 CysS 2+ ), cystamine (H 2 Cyst 2+ ), D,L-homocystine (H 4 hCysS 2+ ), and 3,3 0 -dithiodipropionic acid (H 2 DTDPA) disulfides (Scheme 1) in aqueous solutions. Experimental studies on these reactions (C HCl > 0.1 M) have shown the formation of thiolate complexes of Pt(IV)-[PtCl 4 (S-R) 2 ] and S,S 0 -binuclear complexes of Pt(II)-[Pt 2 Cl 6 (R-SS-R)] [21]. According to spectrophotometric titration, the reaction does not end with the formation of a monocomplex, and a binuclear complex is present in the equilibrium system.…”