Multinuclear (1H, 27Al, and 35Cl) nuclear magnetic resonance studies of solutions of aluminium salts in methanol, aqueous methanol, and aqueous acetone

Abstract

The nature of the ionic species formed when AlCl₃ or Al(ClO₄)₃ is dissolved in anhydrous methanol has been investigated using ¹H, ²⁷Al, and ³⁵Cl n.m.r. spectroscopy. The principal species in AlCl₃ solution is [AlCl₂(MeOH)₄]⁺, although surprisingly, the monochloro-complex does not appear to form. Solutions of Al(ClO₄)₃ contain the hexasolvate which exhibits a remarkably broad ²⁷Al line, presumed to be due to interaction between the anion and the hexasolvated cation. Addition of water to AlCl₃ solutions results in the formation of mono- and di-aquadichloro-complexes although these are quickly and progressively replaced by chloride-free complexes with mixed methanol–water solvation spheres. The results indicate that most of the methanol is displaced from the cations when six water molecules per aluminium cation have been added. No tetrahedral aluminium species were detected.