Reactivity of free N-heterocyclic carbenes in dichloromethane

Abstract

The reactivity of free 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (^MeIPr) and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IDipp) in dichloromethane was investigated. ^MeIPr reacts relatively slowly and selectively with the solvent under the formation of imidazolium salt [^MeIPrH]Cl, which was characterised through NMR and IR spectroscopy as well as single crystal X-ray diffraction. Through deuterium labelling experiments the reaction rate was determined. In contrast IDipp reacts unselectively to various imidazolium salts. Due to the slow decomposition rates of ^MeIPr and IDipp in CH₂Cl₂, reactions of the free carbenes with BeBr₂ to [(^MeIPr)BeBr₂], [(^MeIPr)₂BeBr₂] and [(IDipp)BeBr₂] can be performed.