C-N Coupling in N2 Fixation by the Ditantalum Carbide Cluster Anions Ta2C4.

Abstract

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.