Catalytic reduction of dinitrogen to ammonia at a single molybdenum center

Dinitrogen (N-2) was reduced to ammonia at room temperature and 1 atmosphere with molybdenum catalysts that contain tetradentate [HIPTN3N](3-) triamidoamine ligands {such as [HIPTN3N]Mo(N-2), where [HIPTN3N](3-) is[{3,5-(2,4,6-i-Pr3C6H2)(2)C6H3NCH2CH2}(3)N](3-)} in heptane. Slow addition of the proton source [{2,6-lutidinium}{BAr'(4)}, where Ar' is 3,5-(CF3)(2)C6H3] and reductant (decamethyl chromocene) was critical for achieving high efficiency (similar to66% in four turnovers). Numerous x-ray studies, along with isolation and characterization of six proposed intermediates in the catalytic reaction under noncatalytic conditions, suggest that N-2 was reduced at a sterically protected, single molybdenum center that cycled from Mo(III) through Mo(VI) states.