Unstable intermediates. Part 109.—Electron spin resonance data for boron–carbon and nitrogen–carbon π-radicals: a comparison between π1- and π3-radicals

Abstract

The radicals H₂C—BMe₂ and H₂C—BMe₂(NH₃)inγ-irradiated trimethyl boron and its ammonia adduct, have been identified by their e.s.r. spectra. Various R₂CNR₂ radicals have also been prepared by γ-irradiation of amines at 77 K followed by annealing to ca. 130 K. The former have a π¹ structure and the latter a π³ structure. The results suggest that the former are strictly planar and that the latter are locally planar at carbon but slightly pyramidal at nitrogen. It is postulated that the α-proton hyperfine coupling in the amine radicals is a function of the degree of twist about the C—N bond.