Borylene Insertion into Cage B–H Bond: A Route to Electron-Precise B–B Single Bond

A new strategy to construct electron-precise B–B single bond via direct borylene insertion into B–H bond is described. Reduction of bromoborylene stabilized by carborane-fused silylenes with 2 equiv of sodium gives a new compound with a B–B single bond. Both experimental and density functional theory results suggest that such an electron-precise B–B single bond is formed via in situ generated borylene insertion into B–H bond.