Pauling '3-Electron Bonds', 5-Electron 3-Centre Bonding and Some Tetra-Atomic Radicals

Valence-bond structures with Pauling “3-electron bonds” between pairs of atoms may be written down for a number of triatomic radicals. Here we shall examine these types of structures for some radicals with either 17 or 19 valence-shell electrons. For these systems, it is necessary to write down two Pauling “3-electron bond” structures, which participate in resonance. The delocalized molecular orbital equivalent of this resonance involves the construction of three 3-centre molecular orbitals to accommodate five electrons; this is described in Section 6-4.