Oxime Ether Radical Cations Stabilized by N-Heterocyclic Carbenes

Area of Science:

• Organometallic Chemistry
• Radical Chemistry
• Carbene Chemistry

Background:

• N-heterocyclic carbenes (NHCs) are versatile ligands known for stabilizing various chemical species.
• Nitric oxide (NO) derived radicals are reactive intermediates with significant chemical interest.
• The stabilization of main-group radicals by NHCs is an emerging area in chemistry.

Purpose of the Study:

• To explore the reactivity of N-heterocyclic carbene nitric oxide (NHCNO) radicals with electrophiles.
• To synthesize and characterize novel oxime ether radical cations.
• To investigate the role of NHCs in stabilizing main-group radicals.

Main Methods:

• Reaction of NHCNO radicals with silyl and alkyl triflates.
• Structure determination using X-ray crystallography.
• Electron Paramagnetic Resonance (EPR) spectroscopy and computational analysis.

Main Results:

• Successful synthesis of oxime ether radical cations from NHCNO radicals and triflates.
• Structural elucidation of the radical cations, confirming their formation.
• Observation of a different reaction pathway with lutidinium triflate, yielding a mixture of products.

Conclusions:

• NHCs effectively stabilize NHCNO radicals, enabling their reaction with electrophiles to form radical cations.
• The study provides new insights into the stabilization of main-group radicals through π-conjugation with NHCs.
• This work expands the known examples of stable singlet carbenes for radical stabilization.