Electron spin resonance spectra of the phosphoranyl radicals ROPF_3

Esr spectra recorded during the liquid-phase photolysis of solutions of PF_3 and F_2O or certain peroxides ROOR are attributed to the phosphoranyl radicals PF_4 and ROPF_3. The magnitudes of the observed ^(31)P and ^(19)F hyperfine interactions in these radicals are indicative of a totally symmetric half-filled molecular orbital in a trigonal bipyramidal framework. With the exception of the tert-butoxy group, the oxyl groups in ROPF_3 invariably occupy an apical position. Variations in the hyperfine interactions of the latter radicals with changes in RO are essentially restricted to those of the ^(31)P nucleus and the apical ^(19)F nucleus, an effect reminiscent of the trans influence of ligands in metal complexes. INDO MO calculations reproduce qualitatively some of the experimental observations.