Nitrite activation to nitric oxide via one-fold protonation of iron(II)-O,O-nitrito complex: relevance to the nitrite reductase activity of deoxyhemoglobin and deoxyhemerythrin.

The reversible transformations [(Bim)3Fe(κ(2)-O2N)][BF4] (3) <-> [(Bim)3Fe(NO)(κ(1)-ONO)][BF4]2 (4) were demonstrated and characterized. Transformation of O,O-nitrito-containing complex 3 into [(Bim)3Fe(μ-O)(μ-OAc)Fe(Bim)3](3+) (5) along with the release of NO and H2O triggered by 1 equiv of AcOH implicates that nitrite-to-nitric oxide conversion occurs, in contrast to two protons needed to trigger nitrite reduction producing NO observed in the protonation of [Fe(II)-nitro] complexes.