An Investigation of AlCl3 Solutions in Ethers by 27Al NMR Spectroscopy
2014
Nöth, Heinrich | Rurländer, Robert | Wolfgardt, Peter
²⁷Al NMR studies of AlCl₃ solutions in diethyl ether reveal the presence of AlCl₄ at high concentrations. This ion can also be recognized besides AlCl₃·OR₂ at low temperature in dilute solutions, while at 25 °C a single signal is observed, which represents the average of all species in solution. More extensive dissociation of AlCl₃ results in tetrahydrofuran. The main species in equilibrium with one another are AlCl₃·2THF, AlCl⁻₄ and AlCl₂(THF)⁺₂.Nearly quantitative dissociation to yield AlCl⁻₄ and [AlClL₅]²⁺ occurs in dilute solutions of AlCl₃ in monoglyme (L reprents one oxygen donor atom); at higher concentration an adduct AlCl₃·L with Al in a tetrahedral environment is also present. This trend towards extensive dissociation is also observed in the solutions of AlCl₃ in diglyme and triglyme. Relative peak areas are in agreement with the formation of a 1:1 electrolyte [AlCl₂L₄]⁺AlCl⁻₄ in diglyme, whereas additional dissociation into [AlClL₅]²⁺ and AlCl⁻₄ occurs in triglyme.
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