Efforts to develop organometallic complexes for catalytic nitrogen reduction have seen significant progress in recent years. However, the strategies for improving the activity of the homogenous catalysts have mainly focused on alternating ligands and metals. Herein, we report that the activity and stability of a PN3P-Mo pincer complex ( ) toward dinitrogen (N2) reduction were greatly enhanced through postmodification of the PN3P pincer framework of its parent complex ( ). A high ratio of NH3/Mo (3525) was achieved in the presence of SmI2 as a reductant. In sharp contrast,  only afforded an NH3/Mo ratio of 21. Moreover, when supported by an anionic pincer ligand,  furnished a high oxidation state Mo(V)-nitride complex via N2 cleavage as a plausible key intermediate in the catalytic process, suggesting a catalytic cycle that may involve different oxidation states (II/V) from those with 10-π electron configuration in the literature.