Gas-phase ion chemistry of borazine, an inorganic analogue of benzene

The gas-phase reactivity of selected ionic species with borazine and of bor azine-derived ions with selected neutrals has been studied by FT-ICR and ab initio computations and related to the corresponding ion chemistry of benz ene. The most basic site of borazine is at nitrogen, and its conjugate acid , H3B3N3H4+, is similar in structure to the benzenium ion, as shown by ab i nitio calculations. H3B3N3H4+ ions undergo H/D exchange of up to four hydro gens with CD3OD and do not isomerize by stepwise 1,2-hydrogen shifts. Proto nation at boron is calculated to be unfavored by 28 kcal/mol with respect t o protonation at nitrogen. The H4B3N3H3+ ions show the features of a [B3N3H 5... H-2](+) complex, prone to dissociation at room temperature. The experi mental gas-phase basicity of borazine is equal to 185.0 +/- 1 kcal/mol. The Lewis basicity toward Me3Si+ places borazine into a linear correlation per taining to model aromatic compounds. The experimental gas-phase acidity is 365.4 +/- 1.5 kcal/mol. The reactions of neutral borazine with protonating, alkylating, and nitrating ions have been characterized and compared with t he corresponding reactions of benzene. B3N3H5+ ions, retaining a cyclic str ucture, react similarly, in some respects, as phenylium ions, C6H5+.