Reversible Ligand-Centered Reduction in Low-Coordinate Iron Formazanate Complexes

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Ligand Design

Background:

• Coordination of redox-active ligands to metals facilitates access to reduced metal complexes.
• Low-coordinate iron chemistry presents unique opportunities for fundamental reactivity studies.

Purpose of the Study:

• To investigate the utility of redox-active formazanate ligands in low-coordinate iron chemistry.
• To characterize the electronic and structural properties of reduced formazanate-iron compounds.
• To explore the impact of ligand-centered reduction on complex reactivity.

Main Methods:

• Synthesis and characterization of iron complexes with formazanate ligands.
• Electrochemical studies to determine reduction potentials.
• Structural analysis via X-ray diffraction.
• Spectroscopic techniques (e.g., UV-Vis, EPR) for electronic structure determination.
• Computational modeling (e.g., DFT) to understand bonding and reactivity.

Main Results:

• Iron(II) precursor reduction occurs at milder potentials compared to analogous β-diketiminate complexes.
• Detailed characterization of the reduced three-coordinate formazanate-iron compound.
• Structural, spectroscopic, and computational data confirm reversible ligand-centered reduction to a formazanate radical dianion.
• The reduced complex exhibits a less negative reduction potential, leading to unique reactivity.

Conclusions:

• Formazanate ligands can effectively stabilize reduced iron species through ligand-centered reduction.
• Electron storage on the formazanate ligand tunes the redox potential of the iron center.
• This tuning enhances reactivity, enabling the formation of a novel N-I bond not observed with non-redox-active ligands.