X-ray absorption spectroscopy and density functional theory studies of ([([H.sub.3]buea)[Fe.sup.III-]X].sub.n-] (X = [S.sub.2-], [O.sup.2-], O[H.sup.-]): Comparison of bonding and hydrogen bonding in oxo and sulfido complexes

Iron L-edge, iron K-edge, and sulfur K-edge X-ray absorption spectroscopy is performed on a series of compounds ([([H.sub.3]buea)[Fe.sup.III-]X].sub.n-] (X = [S.sub.2-], [O.sup.2-], O[H.sup.-]) and the electronic structures are used to correlate to density functional theory calculations. The results have shown that hydrogen bonding to [Fe.sup.IV]-O is less energetically favorable than that to [Fe.sup.III]-O, which reflects the highly covalent nature of the [Fe.sup.IV]-O bond.