Electronic Structure and Ligand Effects on the Activation and Cleavage of N₂ on a Molybdenum Center

Dinitrogen fixation under ambient conditions remains a challenge in the field of catalytic chemistry due to the inertness of N₂. Nitrogenases and heterogeneous solid catalysts have displayed remarkable performance in the catalytic conversion of dinitrogen to ammonia. By introduction of molybdenum centers in molecular complexes, one of the most azophilic metals of the transitional metal series, moderate ammonia yields have been attained. Here, we present a combined multiconfigurational/density functional theory study that addresses how ligand fields of different strengths affect the binding and activation of dinitrogen on molybdenum atoms. First, we explored with MRCI computations the diatomic Mo-N and triatomic Mo-N₂ molecular systems. Then, we performed a systematic examination on the stabilization effects introduced by external NH₃ ligands, before we explore model neutral and charged complexes with different types of ligands (H₂O, NH₃, and PH₃) and their consequences on the N₂ binding and activation.