Migration at Boron Cage for Selective B–H Functionalization of <i>nido</i> ‐Carboranes

Molecular rearrangement provides a powerful pathway to structurally unique and synthetically inaccessible molecules. To date, however, such transformations remain underdeveloped for boron clusters. Herein, we disclose a strategy for the selective functionalization of B-H bonds in nido-carboranes via an unprecedented migration at the boron cage. This process orchestrates a rearrangement of B-O substituted nido-carboranes upon reaction with diverse nucleophiles, including N-heterocycles and thioethers, thus enabling the B-H functionalization at a position that is inaccessible through conventional methods. Its synthetic utility is demonstrated through facile post-modification of drug molecules, synthesis of new boron delivery agents with ¹³C labeling for boron neutron capture therapy (BNCT), and construction of carborane-based luminogens that exhibit aggregation-induced emission (AIE) and efficient reactive oxygen species (ROS) generation. Mechanistic investigations support a pathway involving nucleophile-induced migration at the boron cage, facilitated by a high-valent iodine reagent. This work establishes a paradigm for the B-H bond functionalization of boron clusters via migration at the boron cage, thereby expanding the synthetic toolbox for constructing functional molecules based on boron clusters.