AB-INITIO STUDIES OF ALH3-H2O, ALF3-H2O, AND ALCL3-H2O COMPLEXES

HF/6-31G(d,p) and MP2/6-31G(d,p) calculations were performed to determine minimum-energy structures for the molecular complexes AlH3-H2O, AlF3-H2O, and AlCl3-H2O. The structures are qualitatively similar to that of BF3-H2O, with the H2O molecule leaning toward the Lewis acid in such a way as to eclipse two of the hydrogen/fluorine/chlorine atoms in the AlH3/AlF3/AlC3 moiety. Predicted MP2 binding energies were 90.2 kJ/mol for AlH3-H2O, 139.0 kJ/mol for AlF3-H2O, and 126.5 kJ/mol for AlCl3-H2O, which were all substantially higher than the predicted binding energy of BF3-H2O. Basis set superposition error corrections lowered these binding energies by ca. 10 kJ/mol; however, BSSE was a proportionately smaller component of the binding energy when compared to other AlF3 complexes.