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25 July 2006

  An Octahedral Iron(VI) Complex - A Novel Form of Iron

summary written by Bradley Plummer, SLAC Communication Office


Chemists have synthesized and characterized a new, highly reactive form of iron that promises to deepen our understanding of this important element. Iron is found in abundance in the natural world, and in its ionized form plays a crucial role in virtually all living processes.

An iron atom can have as many as eight valence electrons in its outer shell, but most typically iron has five or six of these valence electrons. The new form of iron, designated iron(VI), has only two electrons in its outer shell, making it very electron deficient and thus highly reactive. Only one other form of iron(VI), ferrate, which is tetrahedrally coordinated by four oxygen atoms, is known. Ferrate is a powerful oxidant, but reacts indiscriminately and thus can be difficult to use. The new species of iron(VI) which is octahedrally coordinated, instead forms a bond with nitrogen, which results in different reactivity, and thus holds promise for industrial and biomedical applications.

"We hope that this complex will have practical advantages over other iron compounds, and we might expect that it does based on its structure," explained John F. Berry, an Alexander von Humboldt postdoctoral fellow at Germany's Max-Planck Institute for Bioinorganic Chemistry in Mulheim. Berry is lead author of the paper describing the new compound, which was originally published in Science Magazine's online publication, Science Express. (

The research team, which included scientists from the Max-Planck Institute for Bioinorganic Chemistry in Germany and the Stanford Synchrotron Radiation Laboratory, conducted x-ray absorption spectroscopy (XAS) experiments at SSRL's Beam Line 9-3 to characterize the new complex. The XAS studies, combined with other spectroscopic results and theoretical calculations, were key in establishing the electronic and geometric structure of this novel compound.

To learn more about this research see the full scientific highlight at: research/highlights_archive/feVI.html

J. F. Berry, E. Bill, E. Bothe, S. DeBeer George, B. Mienert, B. F. Neese, K. Wieghardt, Science 2006, 312, 1937.