Planar three-coordinate iron sulfide in a synthetic [4Fe-3S] cluster with biomimetic reactivity

Abstract

Iron-sulfur clusters are emerging as reactive sites for the reduction of small-molecule substrates. However, the four-coordinate iron sites of typical iron-sulfur clusters rarely react with substrates, implicating three-coordinate iron. This idea is untested because fully sulfide-coordinated threecoordinate iron is unprecedented. Here we report a new type of [4Fe-3S] cluster featuring an iron center with three bonds to sulfides. Although a high-spin electronic configuration is characteristic of other iron-sulfur clusters, the planar geometry and short Fe-S bonds lead to a surprising lowspin electronic configuration at the three-coordinate Fe center as determined by spectroscopy and ab initio calculations. In a demonstration of biomimetic reactivity, the [4Fe-3S] cluster reduces hydrazine, a natural substrate of nitrogenase. The product is the first example of NH 2 bound to an iron-sulfur cluster. Our results demonstrate that three-coordinate iron supported by sulfide donors is a plausible precursor to reactivity in iron-sulfur clusters like the FeMoco of nitrogenase. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

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

“…Addition of 2 equiv of the strong reductant KC 8 to a THF solution of 4 forms an unusual [4Fe-3S] cluster in 22% spectroscopic yield ( Figure S9); the characterization of this [4Fe-3S] cluster was recently described elsewhere. 17 Multiple other uncharacterized products are formed in this reaction, but despite the low yield this result demonstrates that the [2Fe-1S] cluster 4 can be converted to other iron-sulfur clusters, in reactions that apparently result from disproportionation of the core.…”

Atomically Precise Preorganization of Open Metal Sites on Gold Nanoclusters with High Catalytic Performance

“…Chemists have long devoted to mimic enzymes because of their outstanding efficiency and exquisite selectivity. [1][2][3] In enzymes, the electronic and steric environments of active centers are modulated by the surrounding amino acids, [4] and the protein backbone consist of modular iron-sulfur clusters, [5] which maintain coordinative unsaturation as they were supported by a series of rigid cysteine residues. [6,7] In parallel, organic ligands have been used to passivate metal clusters, the so-called ligand-protected metal nanoclusters.…”

Atomically Precise Preorganization of Open Metal Sites on Gold Nanoclusters with High Catalytic Performance

“…Chemists have long devoted to mimic enzymes because of their outstanding efficiency and exquisite selectivity [1–3] . In enzymes, the electronic and steric environments of active centers are modulated by the surrounding amino acids, [4] and the protein backbone consist of modular iron–sulfur clusters, [5] which maintain coordinative unsaturation as they were supported by a series of rigid cysteine residues [6, 7] .…”

“…Ph 3 P ligands, dpa and chloride are ligated to Au 23 core in an asymmetric arrangement. The AuÀP bond lengths are in the range of 2.280( 8)-2.318( 9) , the AuÀCl bond length is 2.367 (8) , and the AuÀN distances fall in the range of 2.15(3)-2.19 (3) . It should be noted that the dpa ligand bridges two gold atoms through the amido N donor and one pyridyl N donor, which is different from the two pyridyl N donors bridging mode found in [Au 32 (Ph 3 P) 8 (dpa) 6 ] (SbF 6 ) 2 .…”