http://www.nature.com/nature/journal/v526/n7571/full/nature15246.html

Binding of dinitrogen to an iron–sulfur–carbon site

• Ilija Čorić,
• Brandon Q. Mercado,
• Eckhard Bill,
• David J. Vinyard
• & Patrick L. Holland

Nature

526,

96–99

(01 October 2015)

doi:10.1038/nature15246

Received

27 May 2015

Accepted

24 July 2015

Published online

23 September 2015

Nitrogenases are the enzymes by which certain microorganisms convert atmospheric dinitrogen (N₂) to ammonia, thereby providing essential nitrogen atoms for higher organisms. The most common nitrogenases reduce atmospheric N₂ at the FeMo cofactor, a sulfur-rich iron–molybdenum cluster (FeMoco)^{1, 2, 3, 4, 5}. The central iron sites that are coordinated to sulfur and carbon atoms in FeMoco have been proposed to be the substrate binding sites, on the basis of kinetic and spectroscopic studies^{5, 6, 7}. In the resting state, the central iron sites each have bonds to three sulfur atoms and one carbon atom. Addition of electrons to the resting state causes the FeMoco to react with N₂, but the geometry and bonding environment of N₂-bound species remain unknown⁵. Here we describe a synthetic complex with a sulfur-rich coordination sphere that, upon reduction, breaks an Fe–S bond and binds N₂. The product is the first synthetic Fe–N₂ complex in which iron has bonds to sulfur and carbon atoms, providing a model for N₂ coordination in the FeMoco. Our results demonstrate that breaking an Fe–S bond is a chemically reasonable route to N₂ binding in the FeMoco, and show structural and spectroscopic details for weakened N₂ on a sulfur-rich iron site.