Unstable intermediates. Part CXXXI. An electron spin resonance study of a range of radicals in irradiated phenylphosphonic dichloride and phenylphosphonothionic dichloride

Abstract

Exposure of the title compounds [PhP(O)Cl₂ and PhP(S)Cl₂] to ⁶⁰Co γ-rays at 77 K gave initially e.s.r. spectra characteristic of the corresponding radical anions. Doublets of lower intensity were assigned to PhP(O)Cl and PhP(S)Cl radicals, the latter being clearly derived from the parent anions. Alone or in various solvents, the oxy-compound gave Cl₂^– on annealing, whereas the sulphur analogue gave PhṖ(S)Cl radicals. The electronic structures of these four phosphorus radicals are discussed in the light of the e.s.r. data. In both cases, the pure compounds gave, on annealing, a species characterised by doublets separated by ca. 1400 G. For dilute solutions in a range of solvents, these species were not formed, and for this and other reasons we conclude that they are radical dimers containing two equivalent or nearly equivalent phosphorus atoms. Possible structures are discussed.