Octaplane: A Saturated Hydrocarbon with a Remarkably Low Ionization Energy Leading to a Cation with a Planar Tetracoordinate Carbon Atom

A planar tetracoordinate carbon atom in a singly-charged saturated hydrocarbon is found for the first time. Ab initio calculations at the HF/6-31G* level predict a planar geometry for the central five-carbon moiety in the octaplane radical cation (1•+). The ionization energy of octaplane (5 eV) is found to be remarkably low for a saturated hydrocarbon; indeed, it is comparable to that of the alkali metals lithium and sodium.