Structures of species formed by sequential methane activation by Ta+: Infrared multiple photon dissociation spectroscopy and ab Initio calculations

Products resulting from the sequential activation of four and five methane molecules by atomic tantalum cations were characterized by gas-phase infrared multiple photon dissociation spectroscopy and density functional theory (DFT) calculations. Tantalum cations were generated using a laser ablation source and reacted with methane in a linear radiofrequency ion trap before mass analysis and spectroscopic interrogation in a Fourier transform ion cyclotron resonance mass spectrometer coupled to the free-electron laser for intracavity experiments (FELICE) beamline. Product ions were irradiated using infrared light over the 300−2000 cm⁻¹ spectral range. Comparisons between the experimental and DFT-calculated spectra enabled structural determination of the products formed. The observed products are (CH₃)₂TaC₂H₂⁺ and (CH₃)₃Ta(C₂H₃)⁺. Formation of these products provides evidence for efficient C−H bond activation and subsequent C−C coupling on the atomic tantalum cation.