Cleavage of the triple N N bond by metal clusters is of fundamental interest and practical importance in nitrogen fixation. Previous studies of N N bond cleavage by gas-phase metal clusters emphasized the importance of the dinuclear metal centers. Herein, the dissociative adsorption of N-2 and subsequent C-N coupling on trinuclear carbide cluster anions V3C4- under thermal collision conditions have been characterized by employing mass spectrometry (collision induced dissociation), cryogenic photoelectron imaging spectroscopy, and quantum chemistry calculations. A theoretical analysis identified a crucial adsorption intermediate with N-2 bonded with the V-3 metal core in the end-on/side-on/side-on (ESS) mode, which most likely enables the facile cleavage of the N N bond. Such a vital N-2 coordination in the ESS mode is a result of symmetry-matched interactions between the occupied orbitals of the metal core and both of the two empty pi* orbitals of N-2. Furthermore, carbon ligands also play a considerable role in enhancing the reactivity of the metal core toward N-2. This study strongly suggests a new mechanism of N N bond cleavage by gas-phase metal clusters.