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

Abstract

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.

Potential of Molecular Catalysts with Electron-Rich Transition Metal Centers for Addressing Long-Standing Chemistry Enigmas

“…Molybdenum-based materials and molecular complexes have been studied extensively due to its presence in nitrogenases. , Our very recent theoretical work on Mo + N 2 and Mo – + N 2 reactions disclosed that Mo can transfer five or six electrons to N 2 cleaving its bond and forming either N 2– Mo­(V)­N 3– or N 3– Mo­(VI)­N 3– . However, the energy of NMoN is higher than that of the Mo­(N 2 ) encounter complex (N 2 weakly interacting with Mo).…”

“…In this work, we discuss the possibility of using molecular catalysts with electron rich metals (dubbed Catalysts with Electron-Rich Metal Atoms or CERMA), formally neutral or anionic. Recent studies of the authors demonstrated by means of quantum chemical calculations that such molecular complexes can have superior performance for the selective conversion of methane to methanol and facile activation of N 2 . The main mechanism and advantages of catalytic cycles mediated by CERMAs are shown in Figure .…”