Can the CH 2BH 2 and CH 3BH radicals, cations and anions be observed by experiment?

Abstract

The structure, thermochemistry, isomerization and dissociation of the CH 2BH 2 and CH 3BH radicals, cations and anions have been explored with a wide range of ab initio levels of computational theory and their formation has been probed by tandem mass spectrometry and RRKM kinetic theory. Calculations predict that CH 2 BH 2 ⌉ + is not an equilibrium structure on the potential energy surface. The CH 3 BH ⌉ + was characterized by its collision-induced dissociation mass spectrum and neutralization–reionization (NR) mass spectrometry was used to generate the CH 3 BH ⌉ • radical. While both CH 2 BH 2 ⌉ • and CH 3 BH ⌉ • are stable with respect to isomerization and dissociation, a relatively low barrier to the 1,2-hydrogen shift means that pure CH 3 BH ⌉ • can only be made cold, and so the above NR experiment likely produces a mixture of neutrals, of which only CH 3 BH ⌉ • can be reionized. Vertical electron attachment to CH 3 BH ⌉ • is endothermic which means the CH 3 BH ⌉ - anion is unlikely to be made from the cation or radical. In addition, the anion lies in a shallow well of only 48 kJ mol −1 and will undergo fast isomerization to CH 2 BH 2 ⌉ - below the dissociation limit.