A Nonheme Sulfur-Ligated {FeNO}⁶ Complex and Comparison with Redox-Interconvertible {FeNO}⁷ and {FeNO}⁸ Analogues

A nonheme {FeNO}⁶ complex, [Fe(NO)(N3PyS)]²⁺, was synthesized by reversible, one-electron oxidation of an {FeNO}⁷ analogue. This complex completes the first known series of sulfur-ligated {FeNO}^6–8 complexes. All three {FeNO}^6–8 complexes are readily interconverted by one-electron oxidation/reduction. A comparison of spectroscopic data (UV/Vis, NMR, IR, Mössbauer, X-ray absorption) provides a complete picture of the electronic and structural changes that occur upon {FeNO}⁶–{FeNO}⁸ interconversion. Dissociation of NO from the new {FeNO}⁶ complex is shown to be controlled by solvent, temperature, and photolysis, which is rare for a sulfur-ligated {FeNO}⁶ species.