Unstable intermediates

The e.s.r. spectrum of γ-irradiated hexamethylphosphoramide (HMPA) at 77 K comprised an outer doublet, assigned to (Me2N)2[graphic omitted]O radicals, and an inner triplet assigned to H2ĊN(Me)PO(NMe2) radicals. On partial annealing, a second doublet appeared which is also assigned to the latter radicals. Those radicals responsible for the central features are thought to have the phosphorus atom close to the radical plane, with strong π-conjugation to nitrogen, whilst those showing a large hyperfine coupling to phosphorus are thought to have a conformation in which overlap with the N–P σ-orbital is at a maximum. The latter radicals may well be N-protonated.The significance of these results with respect to metal-HMPA solutions and the nature of "solvated" electrons in this medium is outlined.