Reversible C-C bond formation between redox-active pyridine ligands in iron complexes

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Coordination Chemistry

Background:

• Iron complexes with bulky ligands offer unique reactivity.
• Understanding electron distribution in metal-ligand systems is crucial for catalysis.
• Pyridine ligands can participate in redox processes.

Purpose of the Study:

• To synthesize and characterize novel iron(I) complexes.
• To investigate the electronic structure and spin density distribution in these complexes.
• To explore the reactivity of coordinated pyridine ligands.

Main Methods:

• Synthesis of L(Me)Fe(Py-R)(2) complexes.
• Structural analysis via X-ray crystallography.
• Spectroscopic characterization (e.g., EPR, Mössbauer).
• Density Functional Theory (DFT) calculations.

Main Results:

• Iron(I) complexes with bulky beta-diketiminate ligands were synthesized.
• Pyridine ligands preferentially accept unpaired spin density.
• The S = 3/2 species is a resonance hybrid of Fe(II)/pyridine radical and Fe(I).
• Unprotected pyridines undergo reversible radical coupling (C-C bond formation).
• A coupled diiron(II) complex stores electrons as a C-C bond in the ligand.

Conclusions:

• The electron storage in ligands via C-C bond formation provides a new paradigm for redox-active ligands.
• This reversible C-C bond formation in pyridine ligands is a key feature of these iron complexes.
• The findings offer insights into electron transfer mechanisms and potential applications in catalysis.