On the alcoholysis of alkyl-aluminum(III) alkoxy-NHC derivatives: reactivity of the Al-carbene Lewis pair versus Al-alkyl

The reaction of a bifunctional hydroxy N-heterocyclic carbene (NHC-OH) ligand with alkyl-aluminum(iii) derivatives appears to be dependent on the precursor used. The expected alkoxy-NHC metallated product is indeed obtained with Al(Bu). In contrast, the sterically hindered [Al(Bu)(OAr)] (OAr = 2,6-di-tert-butyl-4-methylphenoxy) displays reactivity at the carbene and affords an imidazolium-aluminate zwitterion. The non-innocence of the Al-NHC motif is further highlighted by the heterolytic cleavage of the phenol O-H bond across the Al-C bond from Al(O-NHC)X derivatives (X = Bu, OAr).