Catalytic reduction of dinitrogen to ammonia using molybdenum porphyrin complexes

Abstract

Porphyrin complexes are well-known in O₂ and CO₂ reduction, but their application to N₂ reduction is less developed. Here, we show that oxo and nitrido complexes of molybdenum supported by tetramesitylporphyrin (TMP) are effective precatalysts for catalytic N₂ reduction to ammonia, verified by ¹⁵N₂ labeling studies and other control experiments. Spectroscopic and electrochemical studies illuminate some relevant thermodynamic parameters, including the N–H bond dissociation free energy of (TMP)MoNH (43 ± 2 kcal mol⁻¹). We place these results in the context of other work on homogeneous N₂ reduction catalysis.