G3 molecular orbital calculations predict that the insertions of boron into the CH, NH, and CN bonds of methylamine to form CH 2 (BH)NH 2 , CH 3 N(BH)H, and CH 3 BNH 2 are exothermic by 57.6, 93.9, and 111.8 kcal mol -1 , respectively. However, the addition of atomic boron to the N site of methylamine yeilds a weak additon complex CH 3 NH 2 ‚‚B, which is lower in energy than the reactants by only 17.2 kcal mol -1 . The dissociation of CH 3 N(BH)H to CH 3 and HNBH has a low activation energy of 28.7 kcal mol -1 and is the most energetically favored one amomg its three decomposition paths. One of the other two paths yielding the final product CH 3 NB has a rate-determining step with a high endothermicity of 111.4 kcal mol -1 , but the other leading to CNB has one with a high activation barrier of 105.7 kcal mol -1 instead. The conversions of CH 3 BNH 2 to the final products CH 2 BNH and CH 2 BNH 2 are respectively controlled by their endothermicities of 96.9 and 47.7 kcal mol -1 .