An octahedral coordination complex of iron(VI)

The hexavalent state, considered to be the highest oxidation level accessible for iron, has previously been found only in the tetrahedral ferrate dianion, FeO42-. We report the photochemical synthesis of another Fe(VI) compound, an octahedrally coordinated dication bearing a terminal nitrido ligand. Mossbauer and x-ray absorption spectra, supported by density functional theory, are consistent with the octahedral structure having an Fe=N triple bond of 1.57 angstroms and a singlet d(xy)(2) ground electronic configuration. The compound is stable at 77 kelvin and yields a high-spin spin Fe(III) species upon warming.