Use of an electron-reservoir complex together with air to generate N-heterocyclic carbenes.

Imidazolium salts with suitable substituents are readily deprotonated to stable NHC carbenes using the electron-reservoir complex [FeICp(eta6-C6Me6)], 1, in the presence of air (via a superoxide radical anion acting as a base). Less stable NHC carbenes can be conveniently obtained from imidazolium salts using the neutral base [FeIICp(eta5-C6Me5CH2)] obtained from 1 and air.