S–S bond reactivity in metal-perthiocarboxylato compounds

Abstract

While M-percarboxylato species are elusive intermediates, their sulfur containing analogues are known in some cases. The feasibility of isolation of M-perthioacetato compounds allowed, in this work, to obtain new insights into the pathways that follow the reactivity of M–E–ER (E = O, S) fragments. Herein we report on the isolation of two new M-perthioacetato compounds: trans-[Pt(CH₃CS₂S)₂] (1) and [Ni(CH₃CSS)(CH₃CS₂S)] (2), which have been fully characterized, including X-ray structures. Reactivity of these compounds towards PPh₃ has been studied combining UV-vis monitorization and NMR measurements. Overall the accumulated data suggest that the evolution of the perthioacetato ligand in complexes 1 and 2 by reaction with PPh₃ consists of a complex multistep pathway in which the sulfur transfer is preceded by electron transfer. Cyclic voltammetry measurements indicate that the transference of two electrons from the phosphorus to the sulfur atom is not concerted, suggesting that the first step of the reaction with PPh₃ is the monoelectronic electron transfer followed by P–S bond formation. The results presented here show a novel pathway in the field of S–S bond reactivity processes relevant in biological, synthetic systems and in hydrocarbon desulfurization processes.