Coordination model, stability constant, and kinetics study of cystamine and l-cystine with [PdCl₄]²⁻ in hydrochloric aqueous solutions

Palladium(II) Ion Mediated Disulfide/Thiolate Interconversion: Predicting the Disulfide Group State from First Principles

“…Since the true equilibrium constants were not experimentally deter-mined, a direct comparison with DFT results cannot be performed. The experimental values 23 of log K 2,4 for cystine = 6.8 and cystamine = 6.2 complexes satisfactorily agreement with the DFT/PBE0/Def2-SVP//DFT/PBE0/Def2-TZVPD calculated constants: 4.8 and 4.3, respectively.…”

“…Spectrophotometric titrations, performed earlier, indicate substantially different interconversion products, given the original structural similarity of all four disulfides. − We believe this effect is specifically due to the presence of Pd 2+ metal ion, which mediates different RSSR/RSH interconversion mechanisms for different disulfides. Indeed, both l -cystine and cystamine form stable S,N′-binuclear and S,S′,N,N′-tetranuclear complexes without cleavage of the disulfide bond. , In opposite, in the interconversion of dl -homocystine and 3,3′-dithiodipropionic acid, which are homologues of l -cystine, the S–S bond undergoes disproportionation under the same conditions. We show that the cleavage of the disulfide bond upon the interaction of a disulfide with a Pd­(II) is as follows: Reaction proceeds through the formation of an S,S′-binuclear disulfide complex, which undergoes hydrolysis to form a thiolate and sulfinic acid complexes .…”

“…Indeed, both L-cystine and cystamine form stable S,N′-binuclear and S,S′,N,N′tetranuclear complexes without cleavage of the disulfide bond. 20,23 In opposite, in the interconversion of DLhomocystine and 3,3′-dithiodipropionic acid, which are homologues of L-cystine, the S−S bond undergoes disproportionation under the same conditions. We show that the cleavage of the disulfide bond upon the interaction of a disulfide with a Pd(II) is as follows:…”

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

“…We have previously reported no disulfide bond cleavage takes place during the stepwise complex formation of L-cystine (H 4 CysS 2+ ) [13,14] and cystamine (H 2 Cyst 2+ ) [15] with Pd(II) in hydrochloric acid solutions. On the other hand, we have reported irreversible disproportionation takes place during the interaction of homocystine (H 4 hCysS 2+ ) and 3,3'-dithiodipropionic acid (H 2 DTDPA) [16] with Pd 2+ yielding sulfinic (RS(O 2 H)M) and thiol (RSM) complexes.…”

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

“…DFT calculations predicted that the formation of S,S 0 -binuclear complexes is a critical intermediate step for determining reaction pathways. The products of these reactions in aqueous solutions are thiolate and sulfinic acid complexes of Pd(II) [17][18][19][20].…”