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 initio 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 compounds. With the exception of SiH3Na, the inverted forms have been found to be more stable than the tetrahedral structures. The special geometrical features displayed by these inverted structures are analyzed, paying special attention to the information provided by the electron density. The nature of the bonding in these molecules is finally discussed.