A Crystalline B₄N₂ Dewar Benzene as a Building Block for Conjugated B,N-Chains

Dewar benzene, one of the isolable valence isomers C6H6, has been extensively studied since its first synthesis in 1962. By contrast, chemistry inorganic congeners which can be formally gained by replacing skeletal carbon atoms with heteroatoms, less developed despite their peculiar structural and electronic features. Among them, extant B,N-Dewar benzenes are limited to B3N3 system. Herein, we report development example an B4N2 3. As predicted DFT calculations, a judicious selection substituents allows synthesizing Single-crystal X-ray analysis, NMR, computational studies confirmed that 3 possesses high-lying B(sp3)–B(sp3) ?-bond at bridgehead position. Reactions ethylene phenylacetylene proceeded smoothly under mild conditions, affording fused B4C4N2 ring systems (4 5). Structural characterization as well calculations revealed compounds 4 5 involve rigid conjugated (BN)4 tetraene scaffold. Formation demonstrates may serve building block for construction B,N-chains.