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

Abstract

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(ⁱBu)₃. In contrast, the sterically hindered [Al(ⁱBu)(OAr)₂] (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_NHC bond from Al(O-NHC)X₂ derivatives (X = ⁱBu, OAr).