Catalytic Reduction of Dinitrogen to Ammonia at a Single Molybdenum Center

Abstract

This Account explores the catalytic reduction of dinitrogen by molybdenum complexes that contain the [HIPTN₃N]^3- ligand ([HIPTN₃N]^3- = [(HIPTNCH₂CH₂)₃N]^3-, where HIPT = 3,5-(2,4,6-i-Pr₃C₆H₂)₂C₆H₃) at room temperature and pressure with protons and electrons. A total of 7−8 equiv of ammonia is formed out of ∼12 possible (depending upon the Mo derivative employed). No hydrazine is formed. Numerous X-ray studies of proposed intermediates in the catalytic cycle suggest that N₂ is being reduced at a sterically protected, single Mo center operating in oxidation states between Mo^III and Mo^VI. Subtle variations of the [HIPTN₃N]^3- ligand are not as successful as a consequence of an unknown shunt in the catalytic cycle that consumes reduction equivalents to yield (it is proposed) dihydrogen.