Carboranes without Cage Carbons: -Dodecaborate Mimics of Neutral -Carboranes.

Substituted two-dimensional aromatic systems, such as arenes, exhibit well-established reactivity patterns at specific sites, largely due to the pronounced electronic directing effects of attached substituents. In contrast, the regioselectivity of three-dimensional aromatic molecules as a function of substituents remains less understood and documented. In this work, we demonstrate that a series of -dodecaborate ([BH]) cluster isomers containing two -NMe moieties exhibit unprecedented regioselective reactivity at boron vertices farthest from the charged substituents. Through a combination of theoretical and experimental studies, we reveal that these boron clusters display near-perfect regioselectivity with multiple electrophiles, ultimately enabling vertex differentiation chemistry within these systems. This observed phenomenon closely parallels the reactivity patterns typically associated with icosahedral -carboranes, where a carbon-based vertex induces a strong electronic dipole, leading to pronounced vertex-specific reactivity differences at boron sites. Our findings suggest that these modified -dodecaborates serve as electronic analogs of neutral -carboranes, achieving similar electronic directing effects without the need for cage-based carbon atoms. Instead, exopolyhedral substituents alone govern the regioselective behavior, expanding the potential for tailored functionalization in boron cluster chemistry.