Accessing Square Planar Cobalt Nitrenoid Redox Isomers across Three Oxidation States

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Catalysis

Background:

• Cobalt nitrenoid complexes are crucial in chemical transformations.
• Understanding the electronic configuration of cobalt-nitrogen bonds is challenging due to their covalent nature.

Purpose of the Study:

• To synthesize and elucidate the electronic structure of cobalt nitrenoid complexes in a square planar ligand field.
• To investigate the impact of aryl substituents on the electronic properties and reactivity of these complexes.

Main Methods:

• Synthesis of cobalt nitrenoids using a pincer-type ligand and arylazides.
• Structural characterization via X-ray crystallography.
• Electrochemical analysis using cyclic voltammetry.
• Spectroscopic studies including electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy (XAS).
• Computational analysis using density functional theory (DFT).

Main Results:

• A series of terminal cobalt nitrenoids with formal Co(III/IV/V) oxidation states were successfully synthesized and characterized.
• A linear free energy relationship was observed between reduction potentials and nitrene substituent electronic properties.
• Spectroscopic and computational data indicate that the complexes exhibit predominantly [Co(II)-imidyl radical]⁻, [Co(III)-imidyl radical]⁺, and [Co(III)-nitrene adduct]²⁺ character for the formal Co(III/IV/V) species, respectively.

Conclusions:

• The study provides detailed insights into the electronic structure of cobalt nitrenoids in a square planar environment.
• The findings contribute to understanding the metal nitrenoid redox isomerism continuum.
• The synthesized complexes offer a platform for exploring novel catalytic applications.