Proton magnetic resonance studies on some complexes of aluminium halides and 4-substituted pyridines

Abstract

¹ H N.m.r. spectra have been recorded over a temperature range both for melts and benzene solutions of the complexes: 4-Me·C₅H₄N,AlX₃, 4-Et·C₅H₄N,AlX₃, and 4-Prⁿ·C₅H₄N,AlX₃(X = Cl, Br, I). In the molten phase the complexes 4-Et·C₅H₄N,All₃ and 4-Prⁿ·C₅H₄N,All₃ are unusual in that the α-hydrogen signal appears as a broad singlet instead of the expected doublet which is observed for all the other complexes studied. In benzene solution this broadening is observed for all bromide and iodide complexes but is absent in the range of chloride complexes investigated. Examination of the spectra over a temperature range show that in the melts the broad singlet, where observed, may be resolved into a doublet on cooling, whilst the opposite trend tends to occur in solution.