Energy decomposition analysis of the activation barriers. To rationalize the trends described above, we examined the nature and strength of interactions that contribute to the activation barrier by considering a three-step alchemical process that starts with the reactant and ends with the transition state. Starting from the reactant geometry, we first separated methane and gallium imide while keeping their geometries fixed. The energy change in this step ∆E SEP , which arises mostly from van der Waals interactions, is small and similar for all gallium imides considered. Second, we distorted methane and the gallium imide to their transition state geometries, and denoted the energy change in this process as ∆E GD . Finally we brought the distorted methane and gallium imide together to their transition state distances, calling the energy change the interaction energy ∆E IN T .