Investigations of the intrinsic properties of gas-phase transition metal nitride (TMN) ions represent one approach to gain a fundamental understanding of the active sites of TMN catalysts, the activities and electronic structures of which are known to be comparable to those of noble metal catalysts. Herein, we investigate the structures and reactivities of the triatomic anions HNbN- by means of mass spectrometry and photoelectron imaging spectroscopy, in conjunction with density functional theory calculations. The HNbN- anions are capable of activating CH4 and C2H6 through oxidative addition, exhibiting similar reactivities to free Pt atoms. The similar electronic structures of HNbN- and Pt, especially the active orbitals, are responsible for this resemblance. Compared to the inert NbN-, the coordination of the H atom in HNbN- is indispensable. New insights into how to replace noble metals with TMNs may be derived from this combined experimental/computational study.