The neutral azatricarbaborane 7-t-Bu-arachno-7,1,5,12-NC(3)B(8)H(12), isolated as a side product (yield 2%) from the new synthesis of 7-t-BuNH2-nido-7,8,9-C(3)B(8)H(10) (yield 70%), can be easily converted to the first parent representatives of the 10-vertex nido family of tricarbaboranes, [5,6,9-C(3)B(7)H(10)]- and 5,6,9-C(3)B(7)H(11).