Oxyfluorides and Basic Fluorides of Aluminium

Abstract

EARLIER¹, we reported the fact that despite the numerous syntheses of aluminium oxyhalides of the type AlOCl, AlOBr and AlOI, by methods generally applicable to all these aluminium oxyhalides, no preparation of AlOF has been reported. After experimental investigations on a number of reactions that might by analogy lead to the formation of AlOF, we have concluded that the lack of information concerning AlOF is not accidental, but stems from the general inapplicability with respect to AlOF of most preparative methods for AlOX compounds. This results from the greater bond strength of aluminium–fluorine bonds as compared with other aluminium–halogen bonds, the high crystallization energy of aluminium fluoride as compared with the other AlX₃ compounds, and the enhanced ability of fluorine to form higher complex anions with elements such as arsenic. It is the latter characteristic which prevents the use of the As₂O₃ + 3A1X₃ → 3AlOX + 2AsX₃ reaction with aluminium fluoride¹.