Theoretical evidence for P—S and P—N p π— p π bonding within the heterocyclopentadienyl framework

SCF and Møller–Plesset calculations have been carried out for systems containing P—S and P—N pπ—pπ bonds: namely, the 1,3,2-dithiaphospholium cation, the 1,3,2-diazaphospholium cation, and the 1,3,2-azathiaphospholium cation. The computed geometries are reported, along with Mulliken atomic charges and selected vibrational frequencies. ΔH 0 values for heterolytic P—H bond dissociation and for isodesmic bond separation reactions provide information on the energetics and stabilization of the P—S and P—N pπ—pπ bonds. Keywords: SCF and MP2 calculations, third period pπ—pπ bonding, bond separation reactions.