Extensive Redox Non-Innocence in Iron Bipyridine-Diimine Complexes: a Combined Spectroscopic and Computational Study

Metal-ligand cooperation is an important aspect in earth-abundant metal catalysis. Utilizing ligands as electron reservoirs to supplement the redox chemistry of the metal has resulted in many new exciting discoveries. Here, we demonstrate that iron bipyridine-diimine (BDI) complexes exhibit an extensive electron-transfer series that spans a total of five oxidation states, ranging from the trication [Fe(BDI)](3+) to the monoanion [Fe(BDI](-1). Structural characterization by X-ray crystallography revealed the multifaceted redox noninnocence of the BDI ligand, while spectroscopic (e.g., Fe-57 Mossbauer and EPR spectroscopy) and computational studies were employed to elucidate the electronic structure of the isolated complexes, which are further discussed in this report.

Automated summary

Metal-ligand cooperation is crucial in earth-abundant metal catalysis, with ligands acting as electron reservoirs to enhance redox chemistry. Iron BDI complexes were found to exhibit a wide range of oxidation states, with structural characterization revealing the redox noninnocence of the BDI ligand. Spectroscopic and computational studies further elucidated the electronic structure of the isolated complexes.