An electron localization function investigation of bonding in some simple four-coordinate nitrogen and phosphorus compounds

The bonding in some simple four-coordinate species involving nitrogen and phosphorus has been studied by the electron localization function (ELF) approach and compared to that in their conventionally singly and doubly bonded counterparts. Despite evidence suggesting the presence of a conventional multiple bond in certain cases of the four-coordinate species, the ELF study shows this not to be the case. Rather the situation is better pictured as, for example, in the case of H3PCH2 as [GRAPHICS] where both ionic and covalent interactions are present, a type of bond we term cov-ionic. While the ionic interaction is generally strong, the covalent part can be weak, as in the case of the four-coordinate nitrogen compounds, or strong as in the case of the four-coordinate phosphorus species. The quantum mechanically determined properties of the cov-ionic bonded compounds ave consistent with this picture. (C) 2000 John Wiley & Sons, Inc.