Reduction of Dinitrogen to Ammonia Catalyzed by Molybdenum Diamido Complexes.

[ArN]Mo(N)(O-t-Bu), which contains the conformationally rigid pyridine-based diamido ligand, [2,6-(ArNCH)NCH] (Ar = 2,6-diisopropylphenyl), can be prepared from H[ArN], butyllithium, and (t-BuO)Mo(N). [ArN]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* as the electron source and PhNHOTf as the proton source. Up to ∼10 equiv of ammonia can be formed per Mo with a maximum efficiency in electrons of ∼43%.