Deamination of 7-(Me3N)-nido-7,8,9-C3B8H10 (1a) leads either to the parent tricarbollide anion [nido-7,8,9-C3B8H11](-) (2(-)) or to the neutral tricarbaborane nido-7,8,9-C3B8H12 (2a), together with a small amount of 8-Me-nido-7,8,9-C3B8H11 (2b). Di- and trisubstituted derivatives of 2a, 7-((BuMeN)-Me-t)-10-Me-nido-7,8,9-C3B8H10 (2c), and 7-((BuMeN)-Me-t)-10,11-Me-2-nido-7,8,9-C3B8H9 (2d) were obtained as byproducts from the methylation of both 7-((BuNH2)-N-t)-nido-7,8,9-C3B8H10 (1b) and 7-((BuMeNH)-Me-t)-nido-7,8,9-C3B8H10 (1c) With MeI in THF under reflux. Heating of 1a and 2(-) at 350 degrees C resulted in the rearrangement of the carbons on the open-face to give high yields of the isomeric tricarbollides 10-(Me3N)-nido-7,8,10-C3B8H10 (3a) and [nido-7,8,10-C3B8H11](-) (4(-)), respectively, The structure of 3a was determined by an X-ray diffraction analysis, and the geometries of the parent compounds 2(-), 2a, and 4(-) were optimized at the ab initio MP2(fc)/6-31G* level. The structures of all compounds also were secured by the excellent agreement between the experimental data and the IGLO/NMR calculations of the B-11 chemical shifts for the parent compounds at the DZ//6-31G*, DZ//MP2/6-31G*, and II'//MP2/6-31G* levels.