Initial steps for the thermal decomposition of alkaline-earth metal amidoboranes: a cluster approximation.
A DFT study of thermal decomposition mechanisms of [M(NH2BH3)2]4clusters with M = Mg, Ca, and Sr is presented. Multi-step reaction pathways leading to elimination of the first H2molecule 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 ≤ Sr. Four metal atoms in the cluster form a rigid planar construction that is found to be nearly unchanged during all transformations. Cleavage of the B-H bond in the environment of alkaline-earth metal atoms leads to the "capture" of the released H atom by neighboring metal atoms with the formation of a M3H moiety. While the activation energies for the cleavage of Hδ-can be as low as 14.3, 22.6 and 23.3 kcal mol-1for M = Mg, Ca and Sr, respectively, barriers for the subsequent cleavage of Hδ+via destruction of the M3H moiety are about twice larger.
Inorganic Chemistry Group, Institute of Chemistry, St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg, 199034, Russia. avpomogaeva@cc.spbu.ru.
A V
http://orcid.org/0000-0002-5131-4240
AV
Pomogaeva
Inorganic Chemistry Group, Institute of Chemistry, St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg, 199034, Russia. avpomogaeva@cc.spbu.ru.
A Y
http://orcid.org/0000-0002-1932-6647
AY
Timoshkin