Reactions of a Chromium(III)-Superoxo Complex and Nitric Oxide That Lead to the Formation of Chromium(IV)-Oxo and Chromium(III)-Nitrito Complexes

The reaction of an end-on Cr­(III)-superoxo complex bearing a 14-membered tetraazamacrocyclic TMC ligand, [Cr^III(14-TMC)­(O₂)­(Cl)]⁺, with nitric oxide (NO) resulted in the generation of a stable Cr­(IV)-oxo species, [Cr^IV(14-TMC)­(O)­(Cl)]⁺, via the formation of a Cr­(III)-peroxynitrite intermediate and homolytic O–O bond cleavage of the peroxynitrite ligand. Evidence for the latter comes from electron paramagnetic resonance spectroscopy, computational chemistry and the observation of phenol nitration chemistry. The Cr­(IV)-oxo complex does not react with nitrogen dioxide (NO₂), but reacts with NO to afford a Cr­(III)-nitrito complex, [Cr^III(14-TMC)­(NO₂)­(Cl)]⁺. The Cr­(IV)-oxo and Cr­(III)-nitrito complexes were also characterized spectroscopically and/or structurally.