Redox-Innocent Metal-Assisted Cleavage of S–S Bond in a Disulfide-Containing Ligand

Abstract

Due to their redox capabilities, thiols have an important role in biological oxidative/reductive processes through the formation of disulfides or their oxidation to into sulfenic, sulfinic, or sulfonic derivatives being also relevant for specific enzyme activities. The mechanisms of these biological pathways often involve metal ion(s). In this case, deciphering metal-assisted transformation of the S-S bond is of primary interest. This report details the reactivity of the disulfide-containing 2,6-bis[(bis(pyridylmethyl)amino)methyl]-4-methylmercaptophenyldisulfide (L(Me(BPA)S-S)) ligand with Cu(II) using different experimental conditions (anaerobic, H2O-only, H2O/O2, or O2-only). Crystallographic snapshots show the formation of tetranuclear disulfide, dinuclear sulfinate, and sulfonate complexes. Mechanistic investigations using Zn(II) as control indicate a non-metal-redox-assisted process in all cases. When present, water acts as nucleophile and attacks at the S-S bond. Under anhydrous conditions, a different pathway involving a direct O2 attack at the disulfide is proposed.

Structural Diversity of Coordination Polymers Based on a Heterotopic Ligand: Cu(II)-Carboxylate vs Cu(I)-Thiolate

“…When more extreme conditions of temperature (120 °C) and acidity (1 M) are employed, the formation of copper­(I)-thiolate is favored. The effect of Cu­(II) Lewis acidity on S–S polarization may be involved in the S–S breaking, and then, the redox reaction between Cu­(II) and the thiols results in the formation of 3 . This study shows that the coordination of carboxylates or thiolates is controlled by the synthesis medium rather than by the redox state of the sulfur atoms.…”

Heterocyclic bismuth(iii) compounds with transannular N→Bi interactions as catalysts for the oxidation of thiophenol to diphenyldisulfide

“…60 A radical mechanism has also been proposed using inorganic complexes. 61,62 Taking into account the experimental data collected in this study, a reaction pathway based on a two steps addition of PhSH to bismuth might be proposed (Fig. 7).…”

“…This is also in line with the previous reports considering a radical mechanism. [59][60][61] Up to 70°C no NMR resonance characteristic for water formation has been observed. We attribute this fact to its physical adsorption on the remained solid catalyst, which only at higher temperature is desorbed (see ESI, Fig.…”

Synthesis and Coordination of a Bisphosphine-[NHC-borane] Compound: A Ligand Framework for Bimetallic Structure Featuring a Boron-Bridging Moiety

“…In the field of ligand design, effective strategies were developed for the preparation of bimetallic structures. − Defined molecular multimetallic systems are indeed of high interest to understand and eventually emulate the activity of polymetallic enzymatic or heterogeneous catalysts. In some cases, a ligand framework supporting bimetallic structures incorporates one moiety bridging the two metal centers. − This feature serves both as a structuring site and also as an additional reactive center. O, S, N, and C atoms are usual bridging elements found either in metalloenzymes − and/or in heterogeneous catalysts (Chart a). , …”