C–N Bond Formation from Co-Conversion of N2 and CO2 Mediated by Nb2OH4– Cluster Anions: Importance of Hydride Ligands

Abstract

Constructing C–N bonds directly from N₂ and CO₂ is highly desirable but challenging. Although metal hydrides show promise in N₂ activation and functionalization with CO₂, their precise role in selectively facilitating C–N coupling remains unclear. Herein, we report the C–N bond formation in the co-conversion of N₂ and CO₂ mediated by a dinuclear metal hydride cluster Nb₂OH₄⁻ employing mass spectrometry and quantum chemistry calculations. The key intermediate Nb₂OH₂N₂⁻, derived from the preliminary reaction of Nb₂OH₄⁻ with N₂, could react with CO₂ to form the C–N bond, as evidenced by the detection of fragment ions (NC⁻ and NCO⁻). Mechanistic studies indicate that hydride ligands modulate the electronic structure of metal centers by weakening the reducing ability and enabling moderated CO₂ activation that favors C–N coupling over CO₂ reduction. The work elucidates how controlled metal hydride formation governs electronic structure and reaction pathways, establishing a general design principle for achieving selective N₂–CO₂ coupling and direct C–N bond construction.