Structure and bonding in third-row main group dicarbides C2X (X=K–Br)

Abstract

The molecular structures of third-row main group dicarbides C(2)X (X=K-Br) have been studied by theoretical methods. It is found that K, Ca, and Ga favor C(2v)-symmetric (T-shape) ground states, whereas As, Se, and Br have linear or quasilinear ground states. In the case of germanium. a very flat potential energy surface is found and an L-shape structure seems to be the ground state. Dissociation energies into X+C(2) are relatively high. The main features of these compounds, in particular, the preference for linear or cyclic structures, have been rationalized in terms of the most relevant interactions between the third-row atom and dicarbon with the help of an energy decomposition analysis.