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Activation of Methane by Os + : Guided‐Ion‐Beam and Theoretical Studies
Author(s) -
Armentrout P. B.,
Parke Laura,
Hinton Christopher,
Citir Murat
Publication year - 2013
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201300147
Subject(s) - endothermic process , chemistry , dehydrogenation , dissociation (chemistry) , exothermic reaction , bond dissociation energy , ground state , transition state , atomic physics , kinetic energy , ion , methane , computational chemistry , adsorption , organic chemistry , physics , quantum mechanics , catalysis
Activation of methane by the third‐row transition‐metal cation Os + is studied experimentally by examining the kinetic energy dependence of reactions of Os + with CH 4 and CD 4 using guided‐ion‐beam tandem mass spectrometry. A flow tube ion source produces Os + in its electronic ground state and primarily in the ground spin–orbit level. Dehydrogenation to form [Os,C,2 H] + +H 2 is exothermic, efficient, and the only process observed at low energies for reaction of Os + with methane, whereas OsH + dominates the product spectrum at higher energies. The kinetic energy dependences of the cross sections for several endothermic reactions are analyzed to give 0 K bond dissociation energies (in eV) of D 0 (Os + C)=6.20±0.21, D 0 (Os + CH)=6.77±0.15, and D 0 (Os + CH 3 )=3.00±0.17. Because it is formed exothermically, D 0 (Os + CH 2 ) must be greater than 4.71 eV, and a speculative interpretation suggests the exothermicity exceeds 0.6 eV. Quantum chemical calculations at the B3LYP/def2‐TZVPP level show reasonable agreement with the experimental bond energies and with previous theoretical values available. Theory also provides the electronic structures of the product species as well as intermediates and transition states along the reactive potential energy surfaces. Notably, the structure of the dehydrogenation product is predicted to be HOsCH + , rather than OsCH 2 + , in contrast to previous work.