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%.