Unstable intermediates. Part LXVIII. Electron spin resonance studies of the radicals O3PF– and O2PF2
Abstract
The radicals O3PF– and O2PF2, both isoelectronic with PO42–, have been identified by their characteristic e.s.r. spectra. The former was prepared by γ-irradiation of KPO2F2 crystals containing PO3F2– 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 gav= 2·0100, Aiso(31P)= 43·8 G, and Aiso(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 Aiso(31P) on going from PO42– to O2PF2 is explained in terms of a σ-bond spin-polarisation mechanism.