The title compd. is monoclinic, space group P21/n, with a 5.914(1), b 21.225(3), c 11.207(2) .ANG., and b 102.74(1) Deg; dc = 1.114 for Z = 4. The final R = 0.054 for 1292 reflections. At. coordinates are given. The mol. shows extensive p delocalization throughout the dihydrotetraazaborole ring indicated by equiv. B-N bonds, shortened N-N bonds and a lengthened N:N bond. Intramol. steric interactions are minimized by twisting the Ph group by an interplanar angle of 44.4 Deg relative to the 5-membered ring.