Isolation of a radical dianion of nitrogen oxide (NO)(2-).

Nitric oxide, NO, the diatomic hybrid of dinitrogen and dioxygen, has extensive biochemical, industrial and atmospheric chemistry. The unpaired electron on NO makes it highly reactive and its facile oxidation and reduction to make (NO)(1+) and (NO)(1-), respectively, have been heavily studied. Now the (NO)(2-) dianion has been isolated for the first time from the two-electron reduction of NO by the recently discovered (N(2))(3-) yttrium complex {[(Me(3)Si)(2)N](2)(THF)Y}(2)(micro(3)-eta(2):eta(2):eta(2)-N(2))K. NO reacts with this complex to form {[(Me(3)Si)(2)N](2)(THF)Y}(2)(micro-eta(2):eta(2)-NO), a paramagnetic complex that has an electron paramagnetic resonance spectrum definitive for the (NO)(2-) radical. Density functional theory reveals that a metal d(pi) to ligand pi* interaction is crucial for the stability of this complex, which reacts with additional NO to generate the diamagnetic (ON=NO)(2-) product, {[(Me(3)Si)(2)N](2)Y}(4)(micro(3)-ON=NO)(2)(THF)(2).