Revisiting the solution structure of ceric ammonium nitrate

Area of Science:

• Inorganic Chemistry
• Organic Synthesis
• Materials Science

Background:

• Ceric ammonium nitrate (CAN) is widely used as a single-electron-transfer reagent in organic synthesis.
• Current applications assume a monomeric [Ce(IV)(NO3)6]2- structure for CAN in solution, based on outdated research.
• This traditional view limits understanding of CAN's reactivity and industrial applications.

Purpose of the Study:

• To challenge the long-held assumption of CAN's monomeric structure in solution.
• To elucidate the fundamental structure and reactivity of ceric ammonium nitrate.
• To provide new insights into polynuclear complexes of tetravalent ions.

Main Methods:

• Utilized synchrotron X-ray diffraction for structural analysis.
• Employed Raman spectroscopy to investigate CAN's molecular structure and bonding.
• Analyzed CAN in strong nitric acid solutions to mimic industrial conditions.

Main Results:

• Demonstrated that CAN exists as an oxo-bridged dinuclear complex, not a monomer, even in strong nitric acid.
• Established CAN as a two-electron-transfer reagent and a redox-activated superbase.
• Challenged the 50-year-old assumption regarding CAN's structure and reactivity.

Conclusions:

• The dinuclear structure of CAN fundamentally alters its role as a reagent in organic synthesis.
• Reclassifying CAN as a two-electron reagent and superbase opens new avenues for its industrial applications.
• This study provides critical insights into the stability and behavior of polynuclear complexes involving tetravalent metal ions.