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

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.