C–N Coupling in N₂ Fixation by the Ditantalum Carbide Cluster Anions Ta₂C₄^–

The construction of C–N bonds by the direct incorporation of dinitrogen (N2) instead of ammonia (NH3) into active species is particularly desirable but has been rarely reported. Herein, a ditantalum carbide cluster anion (Ta2C4–) capable of cleaving the NN bond and constructing a C–N bond under mild conditions has been identified using mass spectrometry, photoelectron imaging spectroscopy, and quantum-chemical calculations. The photoelectron spectrum of Ta2C4N2– is remarkably different from that of Ta2C4– and matches the simulated spectrum of the Ta2C4N2– species with an end-on-bonded CN unit. The formation of the C–N bond has also been supported by the CN– fragment observed in the collision-induced dissociation of Ta2C4N2–. The exceptional reactivity of Ta2C4– is ascribed to the low-valent metal center serving as an electron reservoir. This study provides a non-NH3 route to construct C–N bonds by incorporating N2 into carbide compounds to produce nitrogenous species