The origins of the different bonding features in SiH5– and CH5–; a valence bond curve crossing model

Abstract

Valence bond (VB) computations reveal that the difference between the SiH₅^– and CH₅^– title species does not derive from the hypervalency associated with d atomic orbitals, but rather from the ability of Si to utilize efficiently its σ*(Si–H) orbitals for bonding, much more so than C with the σ*(C–H) orbitals, so that SiH₅^– possesses two H–Si–H axial bonds vs. only one such bond for CH₅^–.