27Al NMR studies of the hydrolysis of aluminium(III) chloride in non-aqueous media

Solutions prepared by equibrating solid AlCl3 and benzene have been studied by 27Al NMR spectroscopy. Evidence of hydrolysis of AlCl3 is found, both under nominally anhydrous conditions and in the presence of added H2O. Results are also reported for systems containing added gaseous HCl. The deconvoluted spectra show signals from rapidly exchanging ionic species, identified as H[AlCl4] and H[AlCl3(OH)], and a non-ionic species, formulated as [Cl2Al(OH)]2, and based on an Al2O2 core, is also postulated. This species is structurally related to compounds reported by others in preparative work carried out in nominally anhydrous AlCl3 and benzene. The solution probably also contains Al2Cl6, identified as a very broad resonance whose chemical shift is estimated at approximately 98 ppm, relative to [Al(H2O)6]3+=0.