O<sub>2</sub> Activation by Non-Heme Thiolate-Based Dinuclear Fe Complexes

Published on 2020-02-14T15:08:01Z (GMT) by
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.

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Wang, Lianke; Gennari, Marcello; Cantú Reinhard, Fabián G.; Padamati, Sandeep K.; Philouze, Christian; Flot, David; et al. (2020): O2 Activation by Non-Heme Thiolate-Based

Dinuclear Fe Complexes. ACS Publications. Collection. https://doi.org/10.1021/acs.inorgchem.9b03633