Special features in the study of molecular structure of alkali metal tetrachloroaluminates

An analysis has been made of the effects from the presence of AlCl3 and (MAlCl4)2 molecules in alkali metal tetrachloroaluminate vapor on the results obtained in electron diffraction studies of the structure of MalCl4 molecules (M is an alkali metal). It has been shown that in the vapor formed by vaporization of melts of potassium, rubidium, and cesium tetrachloroaluminates at temperatures of 610, 590, and 570C, respectively, the content of AlCl3 molecules in the vapor is no greater than 10%, which has practically no effect on the magnitudes of the measured molecular parameters of the MAlCl4 molecules. The presence of dimeric molecules (MAlCl4)2 in the vapor has still less effect. With the aim of confirming the bidentate equilibrium configuration of these molecules, a vibration analysis has been performed. The force field that is found on the assumption of the bidentate configuration gives a satisfactory description of the observed experimental frequencies and amplitudes of the vibrations.