Structural and Electronic Characterization of Non-Heme Fe(II)–Nitrosyls as Biomimetic Models of the FeB Center of Bacterial Nitric Oxide Reductase

The detoxification of nitric oxide (NO) by bacterial NO reductase (NorBC) has gained much attention as this reaction provides a paradigm as to how NO can be detoxified anaerobically in cells. However, a clear mechanistic picture of how the heme/non-heme active site of NorBC activates NO is lacking, mostly as a result of insufficient knowledge about the properties of the non-heme iron(II)–NO adduct. Here we report the first biomimetic model complexes for this species that closely resemble the coordination environment found in the protein, using the ligands BMPA-Pr and TPA. The systematic investigation of these compounds allowed us to gain key insight into the electronic structure and geometric properties of high-spin non-heme iron(II)–NO adducts. In particular, we show how small changes in the ligand environment of iron could be used by NorBC to greatly modulate the properties, and hence, the reactivity of this species.