Metallacyclopropene structures identified by IRMPD spectroscopic investigation of the dehydrogenation reactions of Ta+ and TaO+ with ethene

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Species formed in the reactions of Ta+ and TaO+ with ethene are examined spectroscopically using infrared multiple photon dissociation (IRMPD) action spectroscopy. Ta+, TaC2H2+, and TaO+ are all observed to dehydrogenate ethene yielding [Ta,2C,2H]+, [Ta,4C,4H]+, and [Ta,O,2C,2H]+, respectively. For these species, IR action spectra are obtained in the 225–3400 cm−1 range by monitoring fragmentation into the [Ta,2C]+, [Ta,4C,nH]+ (n = 2, 3), and [Ta,O]+ mass channels, respectively. The spectra are assigned to TaC2H2+, Ta(C2H2)2+, and OTaC2H2+ metallacyclopropene species on the basis of comparisons with scaled vibrational spectra from B3LYP/def2-TZVPPD geometry optimized structures. To further elucidate the chemistry observed, complete reaction coordinate pathways having quintet, triplet, and singlet spin for all three dehydrogenation reactions have also been examined.