||I . Deprotonation of arachno -C 2 B 7 H 3 with KH to give K + arachno -C 2 B 7 H 12 - was studied and two reaction mechanisms were proposed. One mechanism involved a direction abstraction of possibly the most acidic hydrogen in the carborane by the strong base. The second mechanism involves an initial incorporation of a hydride ion from the metal hydride to form C 2 B 7 H 14 - . This intermediate which was not isolated would then lose H 2 gas to give aracho -4,5-C 2 B 7 H 12 - . Calculated chemical shifts of several isomers of C 2 B 7 H 12 - and C 2 B 7 H 14 - were not consistent with variant-temperature 1 H, 2 D, 11 B, 13 C NMR spectra of the reaction mixture. II . The rearrangement process of nido -4,5-C 2 B 6 H 10 was studied by studied by computational and low temperature NMR experiments. Nido -4,5-C 2 B 6 H 9 D was prepared and monitored by 2 D and 11 B NMR experiments to calculate a rate constant and an activation energy for the process. A calculated E a of ∼8 kcal/mol from the NMR studies were in agreement with theoretical results.