Crystalline Silylene-Stabilized Diboryne and Siladiborirene

The exploration of main group compounds with multiple bonds has significantly enhanced our understanding of chemical bonding and expanded transition-metal-free bond activation and catalysis. Diborynes, characterized by a boron-boron triple bond (B≡B), represent a particularly challenging area due to boron's limited valence electrons. Here, we report the synthesis and characterization of a silylene-stabilized diboryne (7), expanding the frontier of diboryne stabilization. X-ray diffraction analysis and density functional theory calculations confirm the presence of a B≡B bond in the diboryne. Remarkably, this diboryne undergoes [1 + 2] cycloaddition reactions with dichlorosilylene and terphenyl isocyanide, producing unprecedented siladiborirene (8) and diborirenimine (9), respectively. X-ray diffraction studies show that 8 and 9 bear a three-membered boron-containing heterocycle with a B═B bond, and computational studies reveal their distinct aromatic character.