Activation by Nonheme Iron Complexes: A Monomeric Fe{III)-Oxo Complex Derived From [O.sub.2]

Iron species with terminal oxo ligands are implicated as key intermediates in several synthetic and biochemical catalytic cycles. However, there is a dearth of structural information regarding these types of complexes because their instability has precluded isolation under ambient conditions. The isolation and structural characterization of an iron(III) complex with a terminal oxo ligand, derived directly from dioxygen ([O.sub.2]), is reported. A stable structure resulted from placing the oxoiron unit within a synthetic cavity lined with hydrogen-bonding groups. The cavity creates a microenvironment around the iron center that aids in regulating [O.sub.2] activation and stabilizing the oxoiron unit. These cavities share properties with the active sites of metalloproteins, where function is correlated strongly with site structure.
The activation of [O.sub.2] by Fe(II) complexes is of fundamental importance in biology. Heme and nonheme iron enzymes use [O.sub.2] as the primary oxidant in various biochemical transformations (1-3). In [...]