DFT studies on catalytic dehydrogenation of ammonia borane by Ni(NHC)₂

Abstract

The catalytic dehydrogenation mechanism of ammonia borane (NH3BH3, AB) by Ni N‐heterocyclic carbene (NHC) complexes has been investigated by density functional theory. Two possible mechanisms of the dehydrogenation of NH3BH3 have been theoretically studied: intramolecular reaction at Ni dicarbene and intermolecular reaction at Ni monocarbene and dicarbene. The facile occurrence of the dehydrogenation of AB was demonstrated by the low activation barriers of the rate‐determining step. It was found that the intramolecular pathway is mostly kinetically favorable with lower activation barrier of 15.51 kcal/mol than the intermolecular pathway. Moreover, for intermolecular dehydrogenation of AB, the activation prefers to take place at monocarbene Ni(NHC) catalyst. Copyright © 2014 John Wiley & Sons, Ltd.

The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

“…First-order rate constants were determined, and KIE experiments indicated that both B-H and N-H bonds were being broken in the rate-determining step(s). This report generated considerable The Catalytic Dehydrocoupling of Amine-Boranes and Phosphine-Boranesinterest with regard to mapping the processes occurring using computational methods [103][104][105][106][107]. In particular the non-innocent role of the NHC ligands, by mediating hydrogen transfer from the amine-borane to the Ni centre, and the role of free carbene in dehydrogenation were revealed.…”

Mechanism for Forming B,C,N,O Rings from NH3BH3 and CO2 via Reaction Discovery Computations

“…Analysis of AB reactivity has shown simultaneous two-hydrogen transfers from AB to oxidizing agents − and high reactivity of the resulting NB double bond in NH 2 BH 2 . AB’s special reactivity can be attributed to its protic NH hydrogen and hydridic BH hydrogen.…”

Stepwise basis set selection

“…) are related to carbon dioxide reduction by ammonia borane, a system of interest to carbon‐neutral chemistry and materials development . The polarized BN and BN bonds have been noted as leading to a wide variety of reactivity, which becomes even more complex as CO bonds are introduced as reactive partners . Compared to the previous SBB examples, significant polarizations during reaction means more basis functions will be needed to capture this reactivity.…”