An N.M.R. study of complexes in acetonitrile solutions of aluminium chloride

Abstract

High resolution proton N.M.R. and broadline ²⁷Al N.M.R. studies have been made in very pure 1 M AlCl₃/acetonitrile (AN) solutions containing various concentrations of LiCl. In addition to the observation of additional peaks in the proton spectrum due to coordination of AN, two aluminium resonances were found in 1 M AlCl₃/AN. These two resonances are interpreted in terms of two aluminium containing species, one of which coordinates with acetonitrile, while the other is a Cl^- complex. Addition of LiCl to 1 M AlCl₃/AN decreases the population of the coordinating species relative to the non-coordinating species, showing that the Cl^- complexing interaction is stronger than the coordination interaction. This information has been used in determining the coordination number of Al³⁺ ions in 1 M AlCl₃/acetonitrile.