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 (CH 3 ) 2 TaC 2 H 2 + and (CH 3 ) 3 Ta(C 2 H 3 ) + . Formation of these products provides evidence for efficient C−H bond activation and subsequent C−C coupling on the atomic tantalum cation. • IRMPD spectroscopy is conducted on the [Ta, 4C, 8H] + and [Ta, 5C, 12H] + complexes formed by reaction of Ta + with methane. • Comparison of theoretical calculations with experiment clearly identifies (CH 3 ) 2 TaC 2 H 2 + and (CH 3 ) 3 Ta(C 2 H 3 ) + complexes. • Clear evidence of CH bond activation and CC bond coupling is found. • Theory is used to elucidate the likely mechanisms for formation of both structures.