Activation of Methane by Group 11 (Cu, Ag, Au) and Group 9 (Co, Ir) Transition Metal Atomic Anions

The interactions of transition metal atomic anions (Cu^-, Ag^-, Au^-, Co^-, Ir^-) with methane were investigated via mass spectrometry, anion photoelectron spectroscopy, and quantum chemical calculations. Anion photoelectron spectra of the anionic metal atom-methane molecular complexes, [MCH₄]^-, combined with theoretical calculations showed that Cu^- and Co^- formed both chemisorption, HMCH₃^-, and physisorption (solvation), M^-(CH₄), complexes, while Ag^- and Au^- formed only physisorption complexes due to their high activation barriers. Also, the mass spectrum showed Ir^- reacting with methane forming dehydrogenation products [IrCH_<i>n</i>]^- (<i>n</i> = 0-3) as well as the parent anion complex [IrCH₄]^-. While the anion photoelectron spectrum of [IrCH₄]^- showed the presence of the physisorption complex, Ir^-(CH₄), and evidence for the intermediates, H₃IrCH^- and H₂IrCH₂^-, the theoretically predicted spectral band for the H₄IrC^- reaction product was outside of our experimental range.