[H3AlXH](-) (X = NH, PH, AsH, O, S, and Se) and H3AlYH (Y= OH, SH, SeH, F, Cl, and Br) have been investigated as donor-acceptor complex type at the G2 level of theory. Both staggered and eclipsed conformations have been examined. The G2 energetic results show that the anionic complexes are more stable than the neutral ones. They also show that this stability decreases when descending in the corresponding periodic table column, from nitrogen (or oxygen and fluorine) to arsenic (or selenium and bromine) atoms. The interaction diagrams prove that the evolution of complexation energy depends on the coordination mode. In fact, this is a simple "HOMO-LUMO" interaction for [H3AlXH](-) anionic complexes while for the H-3-AlYH neutral ones it is a result of two interaction types: interaction between a' symmetry fragment molecular orbital (stabilizing) and interaction between a " symmetry fragment molecular orbitals (destabilizing). The NBO analysis shows that there is no correlation between the G2 complexation energy and the transferred charge from donor fragment to acceptor one.