O<sub>2</sub> Activation by Non-Heme Thiolate-Based Dinuclear Fe Complexes WangLianke GennariMarcello Cantú ReinhardFabián G. PadamatiSandeep K. PhilouzeChristian FlotDavid DemeshkoSerhiy BrowneWesley R. MeyerFranc de VisserSam P. DubocCarole 2020 Iron centers featuring thiolates in their metal coordination sphere (as ligands or substrates) are well-known to activate dioxygen. Both heme and non-heme centers that contain iron-thiolate bonds are found in nature. Investigating the ability of iron–thiolate model complexes to activate O<sub>2</sub> is expected to improve the understanding of the key factors that direct reactivity to either iron or sulfur. We report here the structural and redox properties of a thiolate-based dinuclear Fe complex, [Fe<sup>II</sup><sub>2</sub>(LS)<sub>2</sub>] (LS<sup>2–</sup> = 2,2′-(2,2′-bipyridine-6,6′-iyl)­bis­(1,1-diphenylethanethiolate)), and its reactivity with dioxygen, in comparison with its previously reported protonated counterpart, [Fe<sup>II</sup><sub>2</sub>(LS)­(LSH)]<sup>+</sup>. When reaction with O<sub>2</sub> occurs in the absence of protons or in the presence of 1 equiv of proton (i.e., from [Fe<sup>II</sup><sub>2</sub>(LS)­(LSH)]<sup>+</sup>), unsupported μ-oxo or μ-hydroxo Fe<sup>III</sup> dinuclear complexes ([Fe<sup>III</sup><sub>2</sub>(LS)<sub>2</sub>O] and [Fe<sup>III</sup><sub>2</sub>(LS)<sub>2</sub>(OH)]<sup>+</sup>, respectively) are generated. [Fe<sup>III</sup><sub>2</sub>(LS)<sub>2</sub>O], reported previously but isolated here for the first time from O<sub>2</sub> activation, is characterized by single crystal X-ray diffraction and Mössbauer, resonance Raman, and NMR spectroscopies. The addition of protons leads to the release of water and the generation of a mixture of two Fe-based “oxygen-free” species. Density functional theory calculations provide insight into the formation of the μ-oxo or μ-hydroxo Fe<sup>III</sup> dimers, suggesting that a dinuclear μ-peroxo Fe<sup>III</sup> intermediate is key to reactivity, and the structure of which changes as a function of protonation state. Compared to previously reported Mn–thiolate analogues, the evolution of the peroxo intermediates to the final products is different and involves a comproportionation vs a dismutation process for the Mn and Fe derivate, respectively.