Non-heme High-Spin {FeNO}6–8 Complexes: One Ligand Platform Can Do It All

Heme and non-heme iron–nitrosyl complexes are important intermediates in biology. While there are numerous examples of low-spin heme iron–nitrosyl complexes in different oxidation states, much less is known about high-spin (hs) non-heme iron–nitrosyls in oxidation states other than the formally ferrous NO adducts ({FeNO}7 in the Enemark–Feltham notation). In this study, we present a complete series of hs-{FeNO}6–8 complexes using the TMG3tren coligand. Redox transformations from the hs-{FeNO}7 complex [Fe(TMG3tren)(NO)]2+ to its {FeNO}6 and {FeNO}8 analogs do not alter the coordination environment of the iron center, allowing for detailed comparisons between these species. Here, we present new MCD, NRVS, XANES/EXAFS, and Mossbauer data, demonstrating that these redox transformations are metal based, which allows us to access hs-Fe(II)–NO–, Fe(III)–NO–, and Fe(IV)–NO– complexes. Vibrational data, analyzed by NCA, directly quantify changes in Fe–NO bonding along this series. Optical data allow for the ident...