STRUCTURES IN SOLUTION OF ADDUCTS OF HEXAMETHYLPHOSPHORUS TRIAMIDE AND SUBSTITUTED BENZILS

Hexamethylphosphorus triamide has been allowed to react with p,p′-dinitrobenzil, p-chlorobenzil, p,p′-difluorobenzil, p,p′-dimethylbenzil and p,p′-dimethoxybenzil. All of these materials in benzene-d6 had negative δ 31P chemical shifts except for the p,p′-dinitro adduct whose resonance was found at δ + 17.6. In dichloromethane-d2 the resonances ranged from δ + 38.2 for the p,p′-dinitro adduct to δ − 22.5 for the p,p′-dimethoxy adduct. The 13C NMR spectra of these compounds all showed coupling J POCC to the ipso carbons except for the p,p′-dinitro adduct. These data indicate that the p,p′-dinitro adduct is ionizing rapidly and that the others are phosphoranes. On cooling the coupling was lost for the p,p′-difluoro adduct and for the p-chloro adduct. These spectral changes are attributed to rapid ionization which occurs because of the change of the dielectric constant with change in temperature.