Unstable intermediates. Part 168. Electron addition to cyclic phosphazenes

Abstract

Exposure of the following cyclic phosphazenes to ⁶⁰Co γ-rays at 77 K gives electron-gain centres having e.s.r. spectra characteristic of phosphoranyl radicals: N₃P₃X₆(X = Cl or Br), N₃P₃Cl₃(NMe₂)₃ and N₄P₄X₈(X = Cl or Br). This means that, rather than accommodating the extra electron in a delocalised π orbital of a pseudo-aromatic type, the radical anion distorts so that the electron is confined to a single phosphorus atom having a local trigonal-bipyramidal configuration, with the orbital of the unpaired electron on phosphorus directed radially away from the ring.