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

Abstract

Small, coordinatively unsaturated iron-sulfur clusters are conceived as building blocks for the diverse set of shapes for iron-sulfur clusters in biological and synthetic chemistry. Here, we describe a synthetic method for preparing [2Fe-1S] clusters containing two iron(II) ions, which are supported by a relatively unhindered β-diketiminate supporting ligand. The [2Fe-1S] cluster can be isolated in the presence of trimethylphosphine, and the compound with one PMe 3 on each iron(II) ion is crystallographically characterized. The PMe 3 ligands may be removed with B(C 6 F 5) 3 to give a spectroscopically characterized species with solvent ligands. This species is a versatile synthon for [2Fe-2S], [4Fe-3S], and [10Fe-8S] clusters. Crystallographic characterization of the 10Fe cluster shows that it has all iron(II) ions, and the core has two [4Fe-4S] cubes that share a face in a novel arrangement. This cluster also has two iron sites that are coordinated to solvent donors, suggesting the potential for using this type of cluster for reactivity in the future.

Progress toward the Isolation of Late Metal Terminal Sulfides

“…Their syntheses parallel that reported for the oxo congener, [(H 3 buea)Fe(O)] 2– ( 3 ), which was reported in 2000 . Complex 4 features a Fe–S distance of 2.211(1) Å, which, despite the terminal binding mode of the sulfide, is very similar to those observed in bridged Fe sulfides (e.g., 2.2176(7) Å for [( Me L Me )Fe(PMe 3 )] 2 (µ‐S) ( Me L Me = {(2,6‐Me 2 C 6 H 3 )NC(Me)} 2 CMe) , . This lengthening is likely due to the H‐bonding between the S 2– ligand and α'NH protons of the supporting ligand, which is evidenced by the relatively short S⋯α'N distances (3.377(3) Å).…”

“…The first (and thus far only) group 8 terminal sulfide was reported by Borovik and co-workers in 2004 . [59,60] This lengthening is likely due to the H-bonding between the S 2ligand and α′NH protons of the supporting ligand, which is evidenced by the relatively short S/α′N distances (3.377(3) Å). For comparison, complex 3 has much shorter E/α′N distances (2.707(4) Å), which likely reflects its shorter Fe-O bond length, and also the greater charge density on the O atom.…”

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.…”

Structure, reactivity, and spectroscopy of nitrogenase-related synthetic and biological clusters

“…Inspired by this idea, Holland and coworkers isolated a [4Fe-3S] 2À cluster (compound 11, Fig. 5) in which three of the irons are fourcoordinate and one of the iron atoms is a planar threecoordinate site, ligated by only sulfides 78,79 with an average Fe-S bond length of 2.17(1) Å. The EPR measurements of the [4Fe-3S] 2À cluster revealed an S = 1/2 ground state from antiferromagnetic coupling between the four paramagnetic iron centers.…”