Structural characterization of [M,C,2H](+) products formed by reaction of 5d metal cations Pt+ and Ir+ with ethylene oxide and Ta+ with methane using messenger spectroscopy

Structural characterization of gas-phase [M,C,2H]+(M = Ta, Ir, Pt), formed by reacting laser ablationformed M+with ethylene oxide (c-C2H4O) or methane under multiple collision conditions, is achievedusing infrared multiple-photon dissociation (IR-MPD) spectroscopy with the intracavity free-electronlaser FELICE. After product formation, part of the product distribution is complexed with Ar, allowingfor simultaneous recording of IR-MPD spectra of both bare [M,C,2H]+, which dissociates viadehydrogenation, and [M,C,2H]+∙Ar, which loses Ar. Comparison of the spectra with density functionaltheory (DFT) calculations allows for an internally consistent assignment of the spectra to the Ta+CH2(3A00) distorted carbene, Pt+CH2(2A1) carbene, and to the HIr+CH (1A0) carbyne-hydride. Evidence for asymmetric Ta+CH2∙Ar (3B2) complex is also obtained. For Pt and Ir, these structures match those foundin previous work when these species were formed by reaction of M+with methane, CH4and CD4.Under the current conditions, no clear signs of the previously observed Ir+CH2(3A2) carbene product werefound, consistent with its higher energy, especially after Ar complexation. Potential energy surfaces forthe reactions of Pt+and Ir+with c-C2H4O are also computed.