PNNL

Abstract

Products resulting from the sequential activation of 1, 2, 3, and 4 methane molecules by atomic iridium cations were characterized by gas-phase infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations. Iridium cations were generated using a laser ablation source and reacted with methane in a linear radio-frequency ion trap before mass analysis and spectroscopic interrogation in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer coupled to the Free-Electron Laser for IntraCavity Experiments (FELICE) beamline. Product ions were irradiated using IR light over the 250 to 1500 cm-1 range. Comparisons between the experimental spectra and DFT calculated spectra enabled a structural determination of the products formed. The observed products include HIrCH+, Ir(CH2)2+, HsIr(C3H5)+, and Ir(CH3)s(C3H5)+, where the subscript s denotes a syn- orientation of the two ligands. Formation of the latter two products provides evidence for efficient C-H bond activation and subsequent C-C coupling on the atomic iridium cation.