Department of Chemistry, Georgetown University, Washington, DC, USA.
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA.
Nat Chem. 2022 Nov;14(11):1265-1269. doi: 10.1038/s41557-022-01025-9. Epub 2022 Sep 5.
Reduction of nitrite anions (NO) to nitric oxide (NO), nitrous oxide (NO) and ultimately dinitrogen (N) takes place in a variety of environments, including in the soil as part of the biogeochemical nitrogen cycle and in acidified nuclear waste. Nitrite reduction typically takes place within the coordination sphere of a redox-active transition metal. Here we show that Lewis acid coordination can substantially modify the reduction potential of this polyoxoanion to allow for its reduction under non-aqueous conditions (-0.74 V versus NHE). Detailed characterization confirms the formation of the borane-capped radical nitrite dianion (NO), which features a N(II) oxidation state. Protonation of the nitrite dianion results in the facile loss of nitric oxide (NO), whereas its reaction with NO results in disproportionation to nitrous oxide (NO) and nitrite (NO). This system connects three redox levels in the global nitrogen cycle and provides fundamental insights into the conversion of NO to NO.
亚硝酸根（NO）在各种环境中被还原为一氧化氮（NO）、氧化亚氮（NO），最终为氮气（N），包括作为生物地球化学氮循环的一部分在土壤中，以及在酸化的核废料中。亚硝酸根的还原通常发生在氧化还原活性过渡金属的配位球内。在这里，我们表明路易斯酸配位可以显著改变聚氧阴离子的还原电位，使其能够在非水条件下（相对于 NHE 为-0.74V）进行还原。详细的特征证实了硼烷封端的自由基亚硝酸根二阴离子（NO）的形成，其具有 N（II）氧化态。亚硝酸根二阴离子的质子化导致一氧化氮（NO）的容易损失，而其与 NO 的反应导致氧化亚氮（NO）和亚硝酸根（NO）的歧化。该系统连接了全球氮循环中的三个氧化还原水平，为 NO 向 NO 的转化提供了基本的见解。
