Neutral diiron(iii) complexes with Fe₂(μ-E)₂(E = O, S, Se) core structures: reactivity of an iron(i) dimer towards chalcogens

Abstract

Three neutral bis(μ-chalcogenido)diiron(III) complexes, [{(N,N'-Pipiso)Fe(μ-E)}2] (Pipiso(-) = [(DipN)2C(cis-2,6-Me2NC5H8)](-), (Dip = C6H3Pr(I)2-2,6; E = O, S or Se) have been prepared by reactions of the iron(I) dimer [{(μ-N,N'-Pipiso)Fe}2] with O2, S8 or Se∞. Treating the μ-selenido compound [{(N,N'-Pipiso)Fe(μ-Se)}2] with O2 cleanly generated its μ-oxo counterpart, [{(N,N'-Pipiso)Fe(μ-O)}2]. X-ray crystallographic analyses of the compounds showed them to possess Fe2(μ-E)2 core structures with distorted square planar (E = O) or tetrahedral (E = S or Se) iron coordination geometries. Magnetic, (57)Fe Mössbauer spectroscopic and computational studies indicate medium to strong antiferromagnetic coupling between the two high-spin Fe(III) ions in all three compounds.

Oxidized and reduced [2Fe–2S] clusters from an iron(I) synthon

“…The core bond lengths and angles (Table 1) are similar to those reported for other synthetic [2Fe-2S] clusters [24,32,36,37], and biological [2Fe-2S] clusters [8, 38]. …”

“…This is the same reduction method that results in the activation of N 2 if the reduced solution is warmed [34], but the transient iron(I) intermediate can be trapped using elemental sulfur. The oxidation of an iron(I) species with S 8 was very recently reported by Fohlmeister et al ., which also gave a neutral Fe 2 (μ-S) 2 cluster [32]. Synthesis of [LFe(μ-S)] 2 can also be accomplished through the addition of elemental sulfur to [LFe(benzene)], a previously characterized iron(I) complex [35], but this reaction does not go cleanly, making isolation through this method difficult.…”

“…We attribute the relatively positive potential to the fact that [LFe(μ-S)] 2 is not anionic like the other synthetic clusters, while the biological clusters have hydrogen bonding to the coordinated thiolates that dissipates negative charge buildup [49]. The only previously published neutral clusters gave irreversible reductions [28,32]. …”

“…In this contribution, we describe a method in which elemental sulfur oxidizes a transient iron(I) species to give a diferric [2Fe-2S] cluster. A similar synthesis of a [2Fe-2S] cluster from a diiron(I) species was recently published [32]. The monoanionic diketiminate ligand gives the overall cluster the same charge as Rieske clusters (Figure 1).…”

From a Molecular 2Fe‐2Se Precursor to a Highly Efficient Iron Diselenide Electrocatalyst for Overall Water Splitting

“…Unlike isolable 2Fe‐2S clusters, related 2Fe‐2Se clusters are still scarce. In accordance with the seminal work of Holm and coworkers, several Fe‐Se clusters were synthesized with a range of iron nuclearities (2, 3, 4, and 6); thus aiming to understand the electronic effects exerted by heavy elements (such as selenium) in these clusters, and elucidate the function of such elements in biological systems ,,…”