Syntheses and structures of benzo-bis(1, 3, 2-diazaboroles) and acenaphtho-1, 3, 2-diazaboroles. Issue 45 (5th November 2019) - Weber, Lothar
Abstract : 1, 3, 2-Diazaboroles 4 and 7 with extended π-electron systems were synthesised and characterised by single crystal X-ray diffraction and quantum-chemical calculations. Abstract : Colorless crystalline 2, 6-dibromo-4, 8-dimethyl-1, 3, 5, 7-tetraphenylbenzobis(diazaborole) 4 resulted from the cyclocondensation of 3, 6-dimethyl-1, 2, 4, 5-tetraphenylaminobenzene 3d with two equivalents of boron tribromide in the presence of calcium hydride. Synthesis of the dark-red crystalline 2-bromo- N, N ′-bis(diisopropylphenyl)acenaphtho-1, 3, 2-diazaborole 7 was effected by the cyclocondensation of 1, 2-bis( N -2′, 6′-diisopropylphenylimino)acenaphthene (5 ) and boron tribromide with subsequent sodium amalgam reduction of the initially formed burgundy red diazaborolium salt 6 . Compounds 4, 6 and 7 are characterised by elemental analyses, 1 H, 11 B and 13 C NMR spectroscopy, as well as by single X-ray diffraction studies. The electronic structures of 4, 6 and 7 are subject to DFT calculations.