A sterically stabilized Fe I –Fe I semi-rotated conformation of [FeFe] hydrogenase subsite model

International audienceThe [FeFe] hydrogenase is a highly sophisticated enzyme for the synthesis of hydrogen via a biologicalroute. The rotated state of the H-cluster in the [FeIFeI] form was found to be an indispensable criteria foran effective catalysis. Mimicking the specific rotated geometry of the [FeFe] hydrogenase active site ishighly challenging as no protein stabilization is present in model compounds. In order to simulate thesterically demanding environment of the nature’s active site, the sterically crowded meso-bis(benzylthio)-diphenylsilane (2) was utilized as dithiolate linker in an [2Fe2S] model complex. The reaction of theobtained hexacarbonyl complex 3 with 1,2-bis(dimethylphosphino)ethane (dmpe) results three differentproducts depending on the amount of dmpe used in this reaction: [{Fe2(CO)5{μ-(SCHPh)2SiPh2}}2-(μ-dmpe)] (4), [Fe2(CO)5(κ2-dmpe){μ-(SCHPh)2SiPh2}] (5) and [Fe2(CO)5(μ-dmpe){μ-(SCHPh)2SiPh2}] (6).Interestingly, the molecular structure of compound 5 shows a [FeFe] subsite comprising a semi-rotatedconformation, which was fully characterized as well as the other isomers 4 and 6 by elemental analysis,IR and NMR spectroscopy, X-ray diffraction analysis (XRD) and DFT calculations. The herein reportedmodel complex is the first example so far reported for [FeIFeI] hydrogenase model complex showing asemi-rotated geometry without the need of stabilization via agostic interactions (Fe⋯H–C)