1,5-diaza-2,6-diborabicyclo[3.3.0]octadienes: Products of the reactions of trihaloboranes with ketazines

The 1,5-diazonia-2,6-diboratabicyclo[3.3.0]octa-1(8),4-dienes 1-4 were prepared from dilithiated ketazines and trihaloboranes, BX3 (X = F, Cl, Br, I). Upon elimination of HX the corresponding 1,5-diaza-2,6-diborabicyclo[3.3.0]octa-3,7-dienes were formed and compounds 5 and 6 (X = Cl, Br) were isolated. Treatment of 5 with MeLi and (BuOLi)-Bu-t, respectively, gave 10 and 11. Monocyclic 1,2,3-azaazoniaborata-5-cyclopentenes (7-9: X = F, Cl, Br) resulted from monolithiated ketazines and BX3. The compounds were characterized by NMR spectroscopy (H-1, B-11, C-13, F-19), MS, and elemental analyses (CH). X-ray crystal structure determinations are presented for 1-4 and 11.