Ammonia Activation, H_2 Evolution and Nitride Formation from a Molybdenum Complex with a Chemically and Redox Noninnocent Ligand

摘要

Treatment of the bis(imino)pyridine molybdenum η~6-benzene complex (~(iPr)PDl)Mo(η~6-C_6H_6) (~(iPr)PDI, 2,6-(2,6-iPr_2C_6H_3N=CMe)_2C_5H_3N) with NH_3 resulted in coordination induced haptotropic rearrangement of the arene to form (~(iPr)PDl)Mo(NH_3)_2(η~2-C_6H_6). Analogous η~2-ethylene and η~2-cyclohexene complexes were also synthesized, and the latter was crystallographically characterized. All three compounds undergo loss of the η~2-coordinated ligand followed by N-H bond activation, bis(imino)pyridine modification, and H_2 loss. A dual ammonia activation approach has been discovered whereby reversible M-L cooperativity and coordination induced bond weakening likely contribute to dihydrogen formation. Significantly, the weakened N-H bonds in (~(iPr)PDl)Mo (NH_3) _2 (η~2-C_2H_4) enabled hydrogen atom abstraction and synthesis of a terminal nitride from coordinated ammonia, a key step in NH_3 oxidation.