Reduction of Dinitrogen to Ammonia Catalyzed by Molybdenum Diamido Complexes

[Ar2N3]­Mo­(N)­(O-t-Bu), which contains the conformationally rigid pyridine-based diamido ligand, [2,6-(ArNCH2)2­NC5H3]2– (Ar = 2,6-diisopropyl­phenyl), can be prepared from H2[Ar2N3], butyllithium, and (t-BuO)3Mo­(N). [Ar2N3]­Mo­(N)­(O-t-Bu) serves as a catalyst or precursor for the catalytic reduction of molecular nitrogen to ammonia in diethyl ether between −78 and 22 °C in a batchwise manner with CoCp*2 as the electron source and Ph2NH2OTf as the proton source. Up to ∼10 equiv of ammonia can be formed per Mo with a maximum efficiency in electrons of ∼43%.