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

Abstract

Synthetic [2Fe-2S] clusters are often used to elucidate ligand effects on the reduction potentials and spectroscopy of natural electron transfer sites, which can have anionic Cys ligands or neutral His ligands. Current synthetic routes to [2Fe-2S] clusters are limited in their feasibility with a range of supporting ligands. Here we report a new synthetic route to synthetic [2Fe-2S] clusters, through oxidation of an iron(I) source with elemental sulfur. This method yields a neutral diketiminate-supported [2Fe-2S] cluster in the diiron(III) oxidized form. The oxidized [2Fe-2S] cluster can be reduced to a mixed valent iron(II)-iron(III) compound. Both the diferric and reduced mixed valent clusters are characterized using X-ray crystallography, Mössbauer spectroscopy, EPR spectroscopy and cyclic voltammetry. The reduced compound is particularly interesting because its X-ray crystal structure shows a difference in Fe-S bond lengths to one of the iron atoms, consistent with valence localization. The valence localization is also evident from Mössbauer spectroscopy.

A [2Fe–1S] Complex That Affords Access to Bimetallic and Higher-Nuclearity Iron–Sulfur Clusters

“…Despite our inability to isolate solid samples, solutions of complex 4 can be generated in situ and used as a building block for additional iron sulfide products (Figure 4). Addition of 1/8 equiv of S 8 or 1 equiv of propylene sulfide yields the previously reported diiron(III) [2Fe-2S] complex 16 in 71% or 75% spectroscopic yield, respectively. Compared to the literature synthesis, which proceeds from [L Me FeCl] 2 in 85% spectroscopic yield, 4 is a useful building block for alternative syntheses of the diamond core [2Fe-2S].…”

Reactivity studies on [Cp′Fe(μ-I)]2: nitrido-, sulfido- and diselenide iron complexes derived from pseudohalide activation

“…25c , 32 In addition, the average Fe–S–Fe and S–Fe–S bond angles of 74.60 ± 0.44° and 105.29 ± 0.11° are also at the lower and upper ends of the literature examples. 25c , 32 Consequently the Fe–Fe distance of 2.5873(5) Å is shorter than that in [( meso -phenyl-dibenzimidazolate) 2 Fe 2 (μ-S)] 2– (2.7019(5) Å) 25 c or in [(nacnac)Fe(μ-S)] 2 (nacnac = MeC[C(Me)N(2,6-Me 2 C 6 H 3 )] 2 ) (2.669(1) Å). 32 b The more compact [2Fe–2S] core may manifest itself in the physical properties of 3 , e.g.…”

The influences of carbon donor ligands on biomimetic multi-iron complexes for N2reduction

“…The diamond core in 2 is contracted relative to the one in a previously reported bis(sulde) diiron(III) complex [L Me FeS] 2 , as in 2 the Fe-S bonds are 0.116(2) A shorter and the Fe/Fe distance is 0.641(2) A shorter. 34,35 Importantly, the core of 2 overlays well with the rhomb containing Fe2 and Fe6 in FeMoco, as the Fe-C and Fe-S average bond lengths in both structures are similar (Fe-C avg is 1.994(2) A in 2 vs. 2.00 A in FeMoco; Fe-S avg is 2.217(8) A in 2 and 2.25Å in FeMoco for the Fe2/Fe6 rhomb). 10 The Fe/Fe distance in 2 is 2.6027(6) A, which matches the distances between belt iron atoms in the crystal structure of FeMoco (2.61 A) quite well.…”

“…6a), which also has two high-spin iron(III) centers, but these centers are instead bridged by two sulde ligands. 34 We examined the pre-edge areas at 2470 eV determined by peak tting of the S K-edges, in order to quantify the S 3p character in the unoccupied metal d orbitals. 62 The contribution from the two bridging sulde ligands in [L Me FeS] 2 is 14% S 3p and the contribution from the single bridging sulde ligand in 2 is 6%.…”