Reductive N ₂ Cleavage and Nitride Insertion Reactivity at Molybdenum Complexes Supported by a Rigid PNP Pincer

Abstract

Abstract Metal‐nitride species represent key reactive intermediates in reductive N 2 cleavage and functionalization. Toward a better understanding of nitride transfer reactivity, we present a series of Mo‐nitride complexes supported by a rigid diphosphino‐acridane pincer ligand. Notably, the stepwise reduction of a Mo IV Cl 3 complex under N 2 allows the isolation of a bridging diazenido intermediate as well as a dinuclear Mo‐nitride species ( 4 ) accommodating a bridging N 2 moiety. This is the first example of a Mo(IV) nitride‐N 2 species, and extensive 15 N‐labeling studies were performed to characterize the bridging dinitrogen, diazenido, and nitride moieties. The structure of 4 adopts two orthogonal π‐backbonding interactions between N 2 and two structurally rigidified Mo IV (N) fragments featuring a filled d π orbital. Effective π‐backbonding from such a Mo IV (N) fragment leads to the isolation of PMe 3 , CO, and CN t Bu substituted analogues. Further, reactivity of the Mo‐nitride species with π‐acidic CO and isocyanide leads to the formation of Mo II ‐isocyanate and ‐carbodiimide species, respectively. Computational studies suggest that nitride carbonylation proceeds via an associative nitride insertion pathway, encouraging further studies in direct N 2 fixation to value‐added products via nitride functionalization.