Selective Stepwise Reduction of Nitrate and Nitrite to Dinitrogen or Ammonia
Jewelianna M. Moore, Tabitha J. Miller, Manting Mu, Marconi N. Peñas‐Defrutos, Kelly L. Gullett, Lindsey S. Elford, S. Quintero, Max García‐Melchor, Alison R. Fout
Abstract
High Resolution Image Download MS PowerPoint Slide This study reports a method for the selective reduction of NO 3 – and NO 2 – to N 2 or NH 3, extending prior work in our lab where NO 3 – was reduced to NO by [N(afa Cy ) 3 Fe]OTf 2 (N(afa Cy ) 3 = tris(5-cyclohexyl-amineazafulvene-2-methyl)amine, OTf = triflate). The first pathway involves the reduction of NO 2 – to N 2, where the NO generated in the initial step is transformed to N 2 O by PPh 3 and further reduced to N 2 by the [N(afa Cy ) 3 Fe]OTf 2 complex. An alternative pathway showcases the reduction of the bound NO complex, [N(afa Cy ) 3 Fe(NO)] 2+, to NH 3 using chemical reductants, albeit with a modest yield of 29%. Confirmation of the nitrogen source as NO is established through 15 N labeling studies. Hydroxylamine (NH 2 OH) is proposed as a plausible intermediate in the reduction of bound NO, supported by independent NH 2 OH reduction experiments and computational studies. Nature employs a well-orchestrated, stepwise process involving several enzymes to reduce N-containing oxyanions, and this approach provides valuable insights into the stepwise reduction mechanisms of nitrate and nitrite, yielding NH 3 or N 2 as the product.