Bulky groups such as TMS used in Ref. decrease the propensity of imides to dimerize (Figure ). The dimerization energies for all imides that have at least one bulky TMS group remain consistently within the realm of non-bonded interactions with |∆E dim | < 100 kJ mol -1 . Such dimerization energies are much better compared to those for the other R 1 and R 2 substituents with |∆E dim | > 200 kJ mol -1 (Figure ). For example, phenyl and perfluorophenyl substituents in the reference imide (R 1 = Ph, R 2 --C 6 F 5 ) are insufficiently large to block two active centers from approaching each other and forming two strong Ga -N bonds. This results in a strongly exothermic dimerization reaction for the reference imide with ∆E dim = -224 kJ mol -1 (Table ). The reaction becomes significantly more exothermic for the derivative imide C with its highly exposed active center (∆E dim = -558 kJ mol -1 , Figure and Table ).