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

• Published in: Journal of biological inorganic chemistry Vol. 20; no. 5; pp. 875 - 883
• Main Authors: Reesbeck, Megan E., Rodriguez, Meghan M., Brennessel, William W., Mercado, Brandon Q., Vinyard, David, Holland, Patrick L.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2015
• Subjects: Biochemistry; Biomedical and Life Sciences; Iron Compounds - chemical synthesis; Iron Compounds - chemistry; Iron Compounds - metabolism; Iron-Sulfur Proteins - chemical synthesis; Iron-Sulfur Proteins - chemistry; Iron-Sulfur Proteins - metabolism; Life Sciences; Microbiology; Models, Molecular; Original Paper; Oxidation-Reduction; Mixed valence; Diketiminate; Model cluster; Mössbauer spectroscopy; Iron–sulfur cluster
• DOI: 10.1007/s00775-015-1272-4
• ISSN: 0949-8257

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. Graphical abstract