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Dual Electron Uptake by Simultaneous Iron and Ligand Reduction in an N-Heterocyclic Carbene Substituted [FeFe] Hydrogenase Model Compound

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posted on 08.08.2005 by Jesse W. Tye, Jonghyuk Lee, Hsiao-Wan Wang, Rosario Mejia-Rodriguez, Joseph H. Reibenspies, Michael B. Hall, Marcetta Y. Darensbourg
An N-heterocyclic carbene containing [FeFe]H2ase model complex, whose X-ray structure displays an apical carbene, shows an unexpected two-electron reduction to be involved in its electrocatalytic dihydrogen production. Density functional calculations show, in addition to a one-electron Fe−Fe reduction, that the aryl-substituted N-heterocyclic carbene can accept a second electron more readily than the Fe−Fe manifold. The juxtaposition of these two one-electron reductions resembles the [FeFe]H2ase active site with an FeFe di-iron unit joined to the electroactive 4Fe4S cluster.