Predicting Dinitrogen Coupling with a Series of Small Molecules Catalyzed by a Pincer Complex

Due to consumption of more than 2% of the world's annual energy supply by Haber-Bosch process and the strongest triple bond (N≡N) in nature, directly coupling N₂ with small molecules is particularly important and challenging, let alone in a catalytic fashion. Here we first demonstrate that a NNN-type pincer phosphorus complex could act as a catalyst to couple dinitrogen with a series of small molecules including carbon dioxide, formaldehyde, N-ethylidenemethylamine, and acetonitrile in the presence of diborane(4) under a mild condition by theoretical calculations. N₂ fixation proceeds via a stepwise mechanism involving initial N₂ activation by diborane(4), followed by intramolecular isomerization to a key intermediate (zwitterion). Such a zwitterion can be used to couple a series of small molecules with activation barriers of 23.5-25.2 kcal mol^-1 . All these findings could be particularly useful for main group chemistry aimed at N₂ activation.