THE GAS COMPLEX MNALF5 AND ITS INFLUENCE ON THE PURIFICATION OF ALF3 BY SUBLIMATION

The gas complex MnAlF5 has been determined mass spectroscopically by t he ions MnAlF5+ and MnAlF4+. The gas complex MnAlF5 is formed above 97 3 K by heating up mixtures of AlF3/MnF2 or AlF3 . 3H(2)O endowed with MN(2+) or by heating up solid MnAlF5 too. At 1008 K the enthalpie of d issociation is 197 kJ/mole. The equilibrium structures of the high spi n molecule MnAlF5 (S = 5/2) were examined with ab initio calculations at the HF-level by comlete gradient optimizing. Two minimum structures were found on the potential energy surface. A bidentate fluorine brid ged structure was found to be the most stable at the HF-level. Vibrati onal frequencies and thermodynamic functions of complex formation were estimated for both minimum structures. The importance of the formatio n of the gas complex for the separation of MnF2 and AlF3 by sublimatio n is discussed.