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., 57Fe Mössbauer and EPR spectroscopy) and computational
studies were employed to elucidate the electronic structure of the
isolated complexes, which are further discussed in this report.