Selective Stepwise Reduction of Nitrate and Nitrite to Dinitrogen or Ammonia

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.