Diiron μ-thiolate complexes that bind N2 across multiple oxidation states: Towards new structural/functional models of nitrogenase

Abstract

While known biol. metallocofactors involved in nitrogen redn. (e.g. FeMoco) invariably contain iron in a sulfur-rich coordination environment, synthetic examples of transition metal model complexes (esp. iron) that bind N while also featuring sulfur donor ligands remain rare. In order to address this deficiency, we have synthesized an unusual series of diiron complexes featuring thiolate and dinitrogen ligands. A new binucleating ligand scaffold is introduced that supports a Fe(SAr)Fe diiron subunit that coordinates two dinitrogen mols. across at least three oxidn. states (Fe(II)Fe(II), Fe(II)Fe(I), and Fe(I)Fe(I)). This scaffold also supports dinitrogen binding with hydride as a co-ligand. Synthetic model complexes of these types are desirable to inform and evaluate hypotheses regarding Fe-mediated nitrogen fixation in biol., and may help to delineate the role of the Fe-SFe unit in facilitating this challenging reaction.