Octacoordinated main-group element centres in a planar cyclic B8 environment: an ab initio study

Density functional theory [B3LYP/6-311G(2df)] calculations predict stable planar structures of the nonclassical compounds XB₈ (X = Si, P⁺) containing central octacoordinated silicon and phosphorus atoms, and a fluxional structure of CB₈ with effective octacoordination of the carbon atom.