Abstract
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.