Heats of formation and bond energies in group III compounds

We present heats of formation and bond energies for Group-III compounds obtained from calculations of molecular ground-state electronic energies. Data for compounds of the form MXn are presented, where M = B, Al, Ga, and In, X = H, CI, and CH3, and n = 1-3. Energies for the B, Al, and Ga compounds are obtained from G2 predictions, while those for the In compounds are obtained from CCSD(T)/CBS calculations; these are the most accurate calculations for indium-containing compounds published to date. In most cases, the calculated thermochemistry is in good agreement with published values derived from experiments for those species that have well-established heats of formation. Bond energies obtained from the heats of formation follow the expected trend (C1 >> CH3 similar to H). However. the CH3M-(CH3)(2) bond energies obtained for trimethylgallium and trimethylindium are considerably stronger (> 15 kcal mol(-1)) than currently accepted values.