Mechanistic Insight into the Nitric Oxide Dioxygenation Reaction of Nonheme Iron(III)–Superoxo and Manganese(IV)–Peroxo Complexes

Reactions of nonheme Fe^III–superoxo and Mn^IV–peroxo complexes bearing a common tetraamido macrocyclic ligand (TAML), namely [(TAML)Fe^III(O₂)]²⁻and [(TAML)Mn^IV(O₂)]²⁻, with nitric oxide (NO) afford the Fe^III–NO₃complex [(TAML)Fe^III(NO₃)]²⁻and the Mn^V–oxo complex [(TAML)Mn^V(O)]⁻plus NO₂⁻, respectively. Mechanistic studies, including density functional theory (DFT) calculations, reveal that M^III–peroxynitrite (M=Fe and Mn) species, generated in the reactions of [(TAML)Fe^III(O₂)]²⁻and [(TAML)Mn^IV(O₂)]²⁻with NO, are converted into M^IV(O) and^.NO₂species through O−O bond homolysis of the peroxynitrite ligand. Then, a rebound of Fe^IV(O) with^.NO₂affords [(TAML)Fe^III(NO₃)]²⁻, whereas electron transfer from Mn^IV(O) to^.NO₂yields [(TAML)Mn^V(O)]⁻plus NO₂⁻.