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, MCH 4 −, combined with theoretical calculations showed that Cu – and Co – formed both chemisorption, HMCH 3 –, and physisorption (solvation), M – (CH 4 ), 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 n − ( n = 0–3) as well as the parent anion complex IrCH 4 − . While the anion photoelectron spectrum of IrCH 4 − showed the presence of the physisorption complex, Ir – (CH 4 ), and evidence for the intermediates, H 3 IrCH – and H 2 IrCH 2 –, the theoretically predicted spectral band for the H 4 IrC – reaction product was outside of our experimental range.