Transition metal complexes with “non-innocent” ligands in the activation of hydrogen sulfide

Substituted o-Aminophenols as Redox-Mediators in the Thiol Oxidation to Unsymmetrical Disulfides

“…Previously, it was found that the interaction of 3,6-di-tert-butylo-benzoquinone or IMQ 4 with H 2 S proceeds by a radical mechanism with hydrogen-atom transfer and the formation of corresponding radicals. 53,58 Following on from these data, we propose the analogical mechanism in case of the interaction between the oxidized form of APH 2 and n-C 3 H 7 SH (Scheme 2). As the result, the symmetrical di-n-propyldisulfide 1 was observed.…”

“…The deprotonation of this intermediate leads to the corresponding radical APH • which can disproportionate to the starting o-aminophenol and the corresponding IMQ (Scheme 1, a), as well as undergo the oxidation under electrochemical conditions to IMQ (Scheme 1, b). 52,53 The conversion of APH 1-5 to IMQ 1-5 is a process requiring two electrons per formula unit regardless of the reaction mechanism. Obviously, the second oxidation step occurs at the more cathodic potential than the first one and the disproportionation pathway leads to regeneration of one equivalent of APH which is again oxidized in the same range of potentials.…”

Removal of Acidic-Sulfur-Containing Components from Gasoline Fractions and Their Simulated Analogues Using Silica Gel Modified with Transition-Metal Carboxylates

“…and water-soluble aldehydes, as well as carboxylates of these metals (acetates and formates), , exhibit a positive effect when used as modifiers of porous carriers in the removal of H 2 S and low-molecular-weight RSH from gas mixtures. We have shown earlier − that complexes of transition metals (Ni, Cr, Pt, and Pd) with quinoid-type redox ligands facilitate the oxidative activation of H 2 S and RSH to the corresponding cation radicals. Subsequent dimerization of sulfur-centered radicals results in polysulfanes from H 2 S and symmetric dialkyl disulfides [M­(RS) 2 ] from RSH.…”