Nitric oxide binds reversibly to the Fe(III) complex of a well-developed tetra-amido macrocyclic ligand. Reaction with NO results in formation of a species consistent with an S = 1 {Fe–NO}6 ground state as characterized by UV-vis, IR, EPR, and Mössbauer spectroscopy. The resultant nitrosyl is labile and dissociates readily upon purging with N2, thus providing a rare example of reversible NO binding to non-heme iron.
