Reactions of Dihaloboranes with Electron-Rich 1,4-Bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadienes

The reactions of electron-rich organosilicon compounds 1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1), 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (2), and 1,1 '-bis(trimethylsilyl)-1,1 '-dihydro-4,4 '-bipyridine (12) withB-amino andB-aryl dihaloboranes afforded a series of novel B=N-bond-containing compounds3-11and13. The B=N rotational barriers of7(>71.56 kJ/mol),10(58.79 kJ/mol), and13(58.65 kJ/mol) were determined by variable-temperature(1)H-NMR spectroscopy, thus reflecting different degrees of B=N double bond character in the corresponding compounds. In addition, ring external olefin isomers11were obtained by a reaction between2and DurBBr(2). All obtained B=N-containing products were characterized by multinuclear NMR spectroscopy. Compounds5,9,10a,11, and13awere also characterized by single-crystal X-ray diffraction analysis.