Redox Interconversion between Cobalt(III) Thiolate and Cobalt(II) Disulfide Compounds

Area of Science:

• Coordination Chemistry
• Organometallic Chemistry
• Bioinorganic Chemistry

Background:

• Cobalt complexes with disulfide and thiolate ligands are crucial in various catalytic processes.
• Understanding the redox behavior of cobalt is essential for designing new catalysts and understanding biological systems.

Purpose of the Study:

• To investigate the redox interconversion between cobalt(III) thiolate and cobalt(II) disulfide compounds.
• To explore the influence of anion exchange on this redox process.
• To compare the reactivity of cobalt with iron in similar ligand systems.

Main Methods:

• Experimental synthesis and characterization of cobalt and iron complexes.
• UV-vis spectroscopy for monitoring redox reactions.
• X-ray crystallography for structural determination.
• Computational studies (DFT) to analyze electronic structure changes.

Main Results:

• Formation of high-spin cobalt(II) disulfide [CoII2(L1SSL1)Cl4] and low-spin cobalt(III) thiolate [CoIII(L1S)(MeCN)2](BF4)2 complexes.
• Anion exchange (Cl- or NCS-) triggers reversible redox interconversion between Co(II) and Co(III) states.
• Computational analysis reveals changes in metal d-orbital and sulfur p-orbital contributions upon anion exchange.
• Structural differences observed between analogous dinuclear iron(II) and cobalt(II) disulfide compounds.
• Iron complexes did not yield the expected Fe(III) thiolate compound under similar conditions.

Conclusions:

• Demonstrated an unprecedented anion-triggered redox interconversion between high-spin Co(II) disulfide and low-spin Co(III) thiolate compounds.
• Highlighted the significant role of the counter-anion in modulating cobalt's redox state and electronic properties.
• Showcased distinct reactivity patterns between cobalt and iron with the disulfide ligand, suggesting unique coordination preferences.