π-Bonding in cyclic phosphonitrilic compounds

Abstract

The relationship between the island and delocalised models of the π-electronic structure of cyclic phosphonitrilics is established. In the case of the cyclic trimer, the equivalent orbitals may be localised over three-centre PNP groupings, as required in the island model, only by selecting a particular non-variationally determined set of LCAO parameters. The consequences of this approximation are discussed from the viewpoints of both models.