1,2-Azaborine Cations**

1,2-Dihydro-1,2-azaborine is a six-membered aromatic heterocycle that is isoelectronic with benzene through the replacement of a C=C unit in benzene with an isoelectronic B–N unit.[1,2] Since the pioneering work by Dewar et al.,[3,4] significant advances have been made in the synthesis and reactivity studies of this family of heterocycles.[5–7] Our continued exploration of the 1,2-azaborine motif[8–15] has led us to consider the synthesis of cationic 1,2-azaborines, for which no examples have been reported. In particular, we envisioned that substitution of 1,2-azaborine on the boron atom with pyridine derivatives would furnish cationic biaryl-type structures[16] having the potential for use in materials applications (Scheme 1). Herein we report the synthesis, structural characterization, and optoelectronic properties of pyridine-substituted 1,2-azaborine cations, including a cationic heterocyclic analogue of para-terphenyl. We have previously established nucleophilic substitution of the B–Cl bond in 1,2-azaborines by anionic nucleophiles (with Cl − serving as the leaving group).[8] Less reactive neutral nucleophiles did not displace the chloride from the boron atom. We hypothesized that a better leaving group on the boron atom (e.g., OTf) could render it susceptible to nucleophili