G2(MP2) investigation of alane-[X(CH3)(3)](-) (X = C, Si, and Ge) and alane-Y(CH3)(3) (Y = N, P, and As) interactions

Alane-[X(CH3)(3)](-) (X = C, Si, and Gel and alane-Y(CH3)3 (Y = N, P, and A s) have been investigated as donor-acceptor complex types at the G2(MP2) le vel of theory. The results show that the anionic complexes are more stable than the neutral ones. They show also that this stability decreases when go ing from carbon to germanium for [H3AlX(CH3)](-) complexes and from nitroge n to arsenic for H3AlY(CH3)(3) complexes. The interaction diagrams prove th at the evolution of complexation energy depends on the coordination mode. I n fact, it is a result of two interaction types: interaction between "a(1)" symmetry fragment molecular orbit al (stabilizing) and interactions betwee n "e'' symmetry fragment molecular orbital (destabilizing). The NBO analysi s suggests that there is no correlation between the charge transfer and the complexation energy. It also shows that the shortening of the X(Y)-C bond lengths, upon complexation, is due to the increasing "s" character of these bonds.