Halide ion capture by radicals. Electron spin resonance spectra of R3P·—hal and R2S·—hal σ* radicals

Abstract

Exposure of methanolic or acidic aqueous glasses containing halide salts together with organic phosphines or sulphides gave the electron loss centres R₃P^˙+ or R₂S^˙+ which reacted with halide ions (hal^–) to give the σ^* radicals R₃P·—hal and R₂S·—hal which were identified by e.s.r. spectroscopy. These were formed in competition with the σ^* dimer radicals R₃P·—PR₃⁺ and R₂S·—SR₂⁺, also detected by e.s.r. spectroscopy. Interconversion between these species on annealing the glasses above 77 K is discussed. These reactions are significant in being the reverse of dissociative electron capture. Also, they constitute a method of converting an electron-loss centre into an electron excess centre.