Structures and bonding in silane derivatives with one alkali atom

The structures of silane derivatives with one alkali atom M, SiX3M, where X stands for hydrogen or halogen atoms and M is Li or Na, are studied ab ini tio with uncorrelated and correlated methods and a 6-311++G-(3df,pd) basis set. Geometry, energetics, dipole moments, and topological features of the electron distribution are investigated at the B3LYP/6-311++G(3df,pd) level of the theory for both tetrahedral and inverted structures of these compoun ds. With the exception of SiH(3)Ma, the inverted forms have been found to b e more stable than the tetrahedral structures. The special geometrical feat ures displayed by these inverted structures are analyzed, paying special at tention to the information provided by the electron density. The nature of the bonding in these molecules is finally discussed.