The significance of acid-base properties in the key ligand for hydrogenation: role of amido ligand

Using the density functional theoretical calculations, a series of aliphatic amido pincer based Mn-complexes are proposed for base-free hydrogenation. We report here that the acid-base nature of the amido ligand plays a crucial role in heterolytic cleavage and proton transfer mechanism. The reaction free energy barrier values suggest that such amido ligand-assisted hydrogenation requires a lower activation barrier compared to the previously reported noble and non-noble metal-based catalysts. Furthermore, the Mn-NNN complex is the most promising catalyst by far and this could be due to the optimum acid-base nature of the amido ligand. Such acid-base properties of the pincer ligand can be tuned by ligand substitution, which in turn controls the catalytic activity. SYNOPSIS A series of aliphatic amido pincer ligand-based Mn-complexes are proposed for base-free hydrogenation. The acid-base nature of the amido ligand is very important in heterolytic cleavage and proton transfer mechanism. This acid-base property of the amido ligand plays a crucial role in base-free hydrogenation.