Facile and regioselective B–H bond functionalization of carboranes via cage···I(III) interaction

Abstract

The development of innovative strategies for inert B–H bond functionalization of carboranes and exploration of their potential applications represents a central task in organic chemistry. Here, we demonstrate the facile B–H bond functionalization in carboranes through a cage···I(III) interaction between a nido‑carborane cluster and a hypervalent iodine(III) unit. Both experimental and theoretical investigations reveal that the cage···I(III) interaction induces a charge transfer from the boron cage to the iodine moiety, which leads to a significant decrease of the negative charge at the B(9)–H site of nido‑carborane. This facilitates the activation of the B–H bond and subsequent chemical transformations. The unprecedented cage···I(III) interaction offers a similar B–H bond activation mode as metal mediation. Furthermore, the treatment of nido‑carboranes with the iodide(III) reagent of PhI(OAc)₂ affords nido‑carborane-phenyl iodonium zwitterions as versatile synthons, which enable the modular construction of exopolyhedral B–O, B–N, B–P, and B–S bonds of carborane derivatives. This approach provides an efficient and scalable synthetic platform for metal-free and site-selective B–H bond functionalization of nido‑carboranes under mild conditions. Notably, the developed 2D-3D fused structures can be used as ligands for the facile construction of novel boron cluster-fused hetero-polycyclic metal complexes in one step. These compounds demonstrate intriguing photophysical properties including aggregation-induced emission, tunable emission wavelength, and oxygen sensing.