Solvent- and halide- induced (inter)conversion between iron(II)-disulfide and iron(III) thiolate complexes

Disulfide/thiolate interconversion controlled by Cu is proposed to be involved in relevant biological processes. In analogy to Cu, it can be envisaged that Fe also participates in the control of similar biological processes. We describe here Fe complexes that undergo FeIII‐thiolate/FeII‐disulfide (inter)conversion mediated by halide (de)coordination, and by the nature of the solvent. The dinuclear FeII‐disulfide complex [FeII2(LSSL)]2+ ((LS)2−=2,2′‐(2,2′‐bipyridine‐6,6′‐diyl)bis(1,1‐diphenylethanethiolate), (LSSL)2−=the corresponding disulfide ligand) shows solvent‐dependent properties. Whereas in a non‐coordinating solvent (CH2Cl2) the dinuclear FeII‐disulfide complex is the only stable form, in the presence of coordinating solvents like MeCN or DMF it is partly or fully converted into mononuclear FeIII‐thiolate species having a bound solvent molecule ([FeIII(LS)(Solv)]+, Solv=DMF, MeCN). Addition of Cl− to a CH2Cl2 solution containing the FeII‐disulfide dinuclear complex leads to the fast and quantitative formation of a mononuclear FeIII‐thiolate species with a bound Cl−, that is, ([FeIII(LS)Cl]). The reverse reaction can be achieved by addition of Li[[B(C6F5)4]. In relation to the metal–sulfur electronic distribution, the comparison between the redox properties of the Fe, Mn and Co complexes involved in these MIII‐thiolate/MII‐disulfide interconversion processes allow one to rationalize their respective efficiency.