Methane activation by iron-carbide cluster anions FeC₆^-

Laser-ablation-generated and mass-selected iron-carbide cluster anions FeC₆^- were reacted with CH₄ in a linear ion trap reactor under thermal collision conditions. The reactions were characterized by mass spectrometry and density functional theory calculations. Adsorption product of FeC₆CH₄^- was observed in the experiments. The identified large kinetic isotope effect suggests that CH₄ can be activated by FeC₆^- anions with a dissociative adsorption manner, which is further supported by the reaction mechanism calculations. The large dipole moment of FeC₆^- (19.21 D) can induce a polarization of CH₄ and can facilitate the cleavage of C-H bond. This study reports the CH₄ activation by transition-metal carbide anions, which provides insights into mechanistic understanding of iron-carbon centers that are important for condensed-phase catalysis.