A DFT study of thermal decomposition mechanisms of [M(NH2BH3)(2)](4) clusters with M = Mg, Ca, and Sr is presented. Multi-step reaction pathways leading to elimination of the first H-2 molecule are explored at the M06/TZVP level of theory. For all studied M, the clusters adopt similar structures and exhibit similar transformations along the reaction pathways. Their activation energies decrease in the order Mg <Ca