The deprotonation energies of BH5 and AlH5: Comparisons to GaH5

Hypercoordinate boron is most unusual, leading to considerable theoretical and experimental research on the parent BH5 molecule. The deprotonation energies of BH5 and the related molecules AlH5 and GaH5 have been of particular interest. Here the energy differences for XH5→XH4-+H(X=BandAl) are computed to be 332.4 and 326.3 kcal mol−1, respectively, with an aug-cc-pVQZ basis set at the CCSD(T) level of theory. Vibrational frequencies for BH4- and AlH4- are also reported as 1098, 1210, 2263, and 2284 cm−1 and 760, 779, 1658, and 1745 cm−1, respectively, again at the CCSD(T) aug-cc-pVQZ level of theory. Comparisons with the valence isoelectronic GaH5 molecule are made.