Abstract Mass spectrometric analysis of the anionic products of interaction between platinum atomic anions, Pt − , and methane, CH 4 and CD 4 , in a collision cell shows the preferred generation of [PtCH 4 ] − and [PtCD 4 ] − complexes and a low tendency toward dehydrogenation. [PtCH 4 ] − is shown to be H−Pt−CH 3 − by a synergy between anion photoelectron spectroscopy and quantum chemical calculations, implying the rupture of a single C−H bond. The calculated reaction pathway accounts for the observed selective activation of methane by Pt − . This study presents the first example of methane activation by a single atomic anion.