Harnessing o -Carborane to Access the BN-Ketenimine Structure

BN-isosterism provides a powerful concept for constructing BN analogues of classical organic frameworks. Here, we introduce the concept of BN-ketenimines (R 2 C═C═NR′ vs R 2 N═B═NR′) and demonstrate that the unique electronic effect of the o -carboranyl group enables the synthesis and single crystal structural characterization of the first compound that predominantly adopts a BN-ketenimine structure in the solid state, namely, (Me 3 Si) 2 N═B═NCb (Cb = o -carboranyl). DFT calculations reveal that the push–pull effect between the (Me 3 Si) 2 N and o -carboranyl substituents plays a crucial role in reversing the typical electronic preference of iminoboranes, thereby shifting the equilibrium from (Me 3 Si) 2 N─B≡N─Cb to (Me 3 Si) 2 N═B═NCb. Furthermore, this BN-ketenimine serves as a versatile platform for further functionalization, displaying nucleophilic behavior at nitrogen and electrophilic reactivity at boron and readily participating in inorganic-alkyne-based click ( ia click) reactions.