Synthesis\nof Molybdenum Complexes Bearing Pyridine-Based\nPNP-Type Pincer Ligands with Pendent Pyridyl Unit and Their Catalytic\nActivity for Ammonia Formation

Molybdenum trichloride complexes bearing pyridine-based\nPNP-type\npincer ligands with a pendent pyridyl unit as a proton mediating moiety\nare newly designed and synthesized for the aim to promote proton-coupled\nelectron transfer in catalytic ammonia formation from dinitrogen.\nX-ray analysis of the molybdenum trichloride complexes reveals that\nthe pendent pyridyl unit introduced at the benzylic position of the\npyridine skeleton in the pincer ligand is located at an appropriate\nplace for donating protons. Unfortunately, the newly prepared molybdenum\ncomplexes do not work as effective catalysts for ammonia formation.\nIt is considered that the pendent pyridyl unit is unexpectedly coordinated\nto the molybdenum center to suppress the activation of the dinitrogen\nmolecule.