An air-stable N-heterocyclic carbene iminoxyl borate radical zwitterion.

A remarkably stable radical zwitterion derived from N-heterocyclic carbene nitric oxide and B(C6F5)3 is reported. The presented radical was generated by steric and electronic protection of the nitric oxide moiety using B(C6F5)3, which secured its stability toward air and moisture. An analogous yet less stable radical derived from C(C6H5)3+ is also synthesized and characterized.