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Sequential activation of methane by Ir^+: An IRMPD and theoretical investigation

Wheeler, Oscar W. and Salem, Michelle and Gao, Amanda and Bakker, Joost M. and Armentrout, P. B. (2019) Sequential activation of methane by Ir^+: An IRMPD and theoretical investigation. International Journal of Mass Spectrometry, 435 . pp. 78-92. ISSN 1387-3806.

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The sequential activation of up to 4 CH_4 molecules by Ir^+ is investigated through a gas-phase infrared multiple photon dissociation (IRMPD) experiment and theoretical calculations. A molecular beam apparatus was used to generate Ir^+ by laser ablation and expose it to controlled amounts of CH_4. Product ions were irradiated with IR light from a free electron laser over the 500–1800 cm^(−1) spectral range and photodissociation was monitored using a time-of-flight mass spectrometer. Experimental spectra were obtained for five distinct species: [Ir,3C,8 H]^+, [Ir,3C,10 H]^+, [Ir,4C,10 H]^+, [Ir,4C,12 H]^+, and [Ir,O,3C,12 H]^+. To identify these species, B3LYP/def2-TZVPPD geometry optimizations were performed on a variety of possible structures, with computed IR spectra compared to the experimental IRMPD spectra. This has led to the following assignments: [Ir,3C,8 H]^+ = IrCH_2(CH_3)_2^+, [Ir,3C,10 H]^+= HIr(CH_3)_3^+, [Ir,4C,10 H]^+ = Ir(CH_3)_2(C_2H_4)^+, [Ir,4C,12 H]^+ = a mixture of HIr(CH_3)(C_2H_4)^+(CH_4), HIr(CH_3)_2(C_2H_5)^+, Ir(CH_3)_4^+, and (H_2)Ir(CH_3)_2(C_2H_4)^+, and [Ir,O,3C,12 H]^+ = (H_2O)HIr(CH_3)_3^+. Notably, evidence for C-C coupling is observed upon reaction with a fourth methane. Mechanisms for the formation of the observed products were also explored computationally by examining the reaction coordinate pathways for the reactions of methane with HIrCH^+, IrCH_2^+, Ir(CH_3)_2^+, HIrCH_2(CH_3)^+, HIr(CH_3)_3^+, and IrCH_2(CH_3)_2^+.

Item Type:Article
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URLURL TypeDescription
Wheeler, Oscar W.0000-0002-6269-5587
Gao, Amanda0000-0003-0950-5067
Additional Information:© 2018 Elsevier B.V. Received 12 July 2018, Revised 22 September 2018, Accepted 2 October 2018, Available online 4 October 2018. Financial assistance was provided by the National Science Foundation, Grants No. CHE-1664618 and OISE-1357887. We gratefully acknowledge the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) for the support of the FELIX Laboratory. Finally, the Center for High Performance Computing (CHPC) at the University of Utah is acknowledged for their generous allocation of computing time.
Funding AgencyGrant Number
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Subject Keywords:Methane activation; Infrared multiple photon dissociation; Iridium; Carbon-carbon coupling; Dehydrogenation; Reaction coordinate pathway
Record Number:CaltechAUTHORS:20190109-152937031
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Official Citation:Oscar W. Wheeler, Michelle Salem, Amanda Gao, Joost M. Bakker, P.B. Armentrout, Sequential activation of methane by Ir+: An IRMPD and theoretical investigation, International Journal of Mass Spectrometry, Volume 435, 2019, Pages 78-92, ISSN 1387-3806, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92181
Deposited By: Tony Diaz
Deposited On:10 Jan 2019 12:57
Last Modified:10 Jan 2019 12:57

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