Unstable intermediates. Part LXVIII. Electron spin resonance studies of the radicals O3PF– and O2PF2

Abstract

The radicals O₃PF^– and O₂PF₂, both isoelectronic with PO₄^2–, have been identified by their characteristic e.s.r. spectra. The former was prepared by γ-irradiation of KPO₂F₂ crystals containing PO₃F^2– impurity, and the latter by similar treatment of POF₃ containing HPO₂F₂. Magnetic data for PO₃F^– were g_∥= 2·0274, g_⊥= 2·0085; A_∥(³¹P)=ca. A_⊥=ca. 39·1 G, A_∥(¹⁹F)≈A_⊥=ca. 8·0 G. The radical O₂PF₂, which was rotating relatively rapidly at 77°K, had g_av= 2·0100, A_iso(³¹P)= 43·8 G, and A_iso(¹⁹F)= 52·5 G. The results are discussed in terms of structures in which the unpaired electron is confined to a molecular orbital on the three oxygen atoms of O₃PF^–, but delocalised on to both the oxygen and fluorine atoms in O₂PF₂. The steady increase in A_iso(³¹P) on going from PO₄^2– to O₂PF₂ is explained in terms of a σ-bond spin-polarisation mechanism.