Modelling an Fe-III High-Valent Pincer-type Transition Metal Complex for Dehydrogenation of Ammonia-Borane.

Development of efficient and cost-effective catalysts for the dehydrogenation of Ammonia-Borane (AB) has been a challenge which affects the advancement of the hydrogen economy. Over the last decades, pincer-type transition metal complexes are known to show promising results in catalyzing many chemical reactions ranging from CO2 reduction to C-H bond activation. In this work we investigate the ability of a high-valent Ni-III-Cl complex (complex 1) for the dehydrogenating AB at slightly higher than room temperature. Although the abstraction of H2 from AB can occur at room temperature, higher temperature is required due to relatively higher free-energy barriers for the formation of molecular H2. However, when the Ni-III center is substituted by a Fe-III center (complex 2), AB dehydrogenation can occur at room temperature for one equiv of AB with a free-energetic span of 21.07 kcal/mol. Therefore, for the initial cycle of AB dehydrogenation, the Fe-III complex has better functionality and this work exhibits the impact of metal mono-substitution, specifically Fe in activating AB dehydrogenation at room temperature and further paves the way for simple modelling of transition metal-based complexes as catalysts for such reactions.