EPR data do not support the PO representation for trialkyl phosphates and phosphine oxides or sulfides

Abstract

Almost all representations of phosphates [(RO)₃PO], trialkyl phosphine oxides (R₃PO) and related species include a double bond between phosphorus and oxygen. However, we strongly oppose the double-bond representation and maintain that it is misleading. EPR evidence for electron-loss centres are shown to be in accord with the structures (R)₃⁺P—O˙, with small, negative spin density on phosphorus. Also, electron addition shows that there are no low-lying vacant 3d orbitals available for the excess electrons, which occupy a largely non-bonding σ orbital with high spin-density in the 3s orbital on phosphorus. These results cannot be reconciled with any of the concepts which lead to the PO formulation.