Herein, we report the synthesis and reactivity of BCPIs, equipped with an imidazolium linker for the construction of the cyclic structure, which can neutralize a formal anionic charge generated on a four-coordinate B atom (Figure ). The synthesized BCPIs were successfully applied to provide evidence for two species that were previously missing from contemporary organic chemistry; i.e. a  5 -oxazaphosphetane species that is generated via a formal [2+2] cycloaddition between BCPIs and CO2, and a borenium species with a chloride counterion that is generated via the spontaneous heterolysis of the B-Cl bond in a BCPI-coordinated chloroborane even in the absence of an external halophile.