Issue Date: February 28, 2011
Iron(V) Nitride Mimics Nitrogenase Activity
An international research team has isolated an iron(V) nitride (Fe≡N) complex that readily produces ammonia, mimicking one of the steps nitrogenase enzymes may use to reduce N2 to NH3 (Science, DOI: 10.1126/science.1198315). Chemists are on the lookout for high-oxidation-state iron complexes with metal-ligand multiple bonds as models to study nitrogenase and other enzyme catalytic cycles with the goal of developing efficient industrial catalysts. In these cycles, iron shifts into different oxidation states to bind nitrogen intermediates on the pathway between N2 and NH3. Iron(V) complexes proposed to participate in this process have been exceedingly hard to isolate and study, however. Jeremiah J. Scepaniak and Jeremy M. Smith of New Mexico State University and Karsten Meyer of Friedrich Alexander University, in Erlangen, Germany, and colleagues made their complex by synthesizing an iron(IV) complex containing a tripodal N-heterocyclic carbene ligand and then oxidizing it to iron(V). When the researchers added water and an electron source to the complex, the Fe≡N group protected by the ligand—like the active site of an enzyme—produced ammonia within seconds and formed an iron(II) complex. This reactivity is similar to nitrogenase chemistry in which water supplies hydrogen for ammonia synthesis, the researchers note.
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