Dehydrogenation of Methane by Gas-Phase Os⁺:  A Density Functional Study

Abstract

Density functional calculations have been performed to explore the sextet, quartet, and doublet potential energy surfaces of methane dehydrogenation by gas-phase Os+ for understanding the reaction mechanism. The minimum energy reaction path is found to involve the spin inversion three times in the different reaction steps. Totally, three spin states (sextet, quartet, and doublet) are involved in the whole reaction. Specifically, the reaction is most likely to proceed through the following steps: 6 Os+ + CH4 → OsCH4 + ( 6 1) → HOsCH3 ( 4 2) → HOsH(CH2)+ ( 2 3) → (H2)Os(CH2)+ ( 4 4) → Os(CH2)+ ( 4 5) + H2. The overall reaction is calculated to be exothermic by 4.2 kcal/mol, which is in good agreement with the available experimental results. The first spin inversion, from the sextet state to the quartet state, makes the activation of the first C−H bond energetically spontaneous. The second transition from the quartet state to the doublet state facilitates the cleavage of the second C−H bond, lowering the barrier from 25.9 kcal/mol to 16.1 kcal/mol. The third spin inversion occurs from the doublet state to the quartet state in the reductive elimination step of H2, and this spin inversion leads to a decrease in the barrier height from 41.0 to 30.4 kcal/mol.

Thermodynamic and kinetic properties of scandium (I) ion reacting with SCO in gas phase

“…So far, it is well known that a number of reactions in organic, inorganic and organometallic chemistry, in which two states of different multiplicities are involved on the reaction path, have been verified experimentally [15][16][17]. Dai et al found that the spin inversion might occur in this reaction system, where the spin multiplicity should change from the triplet state to the singlet state in the crossing region and then move to the singlet potential energy surface as the reaction proceeds [10].…”

Carbon dioxide activation by La atom and La+ cation in the gas phase: A density functional theoretical study

“…Actually, the reactions cata- lyzed by metallic systems may often involve a change in the spin states and proceed via a non-adiabatic way on two or more potential energy surfaces [49][50][51], denoted as ''two state reactivity" (TSR) [52], which has been confirmed by experimental studies. In previous theoretical researches about CO 2 activation by Nb + and Zr + cations, Toscano et al have ascertained the presence of some spin inversion during the reaction process, CO 2 activation mediated by metal cations was found to be an exothermic spin-forbidden process resulting from a crossing between different energetic profiles.…”

Theoretical study on the reactions of Nb and Nb+ with CO2 in gas phase

“…Actually, the reactions catalyzed by metallic systems may often involve a change in the spin states and proceed via a nonadiabatic way on two or more potential energy surfaces, denoted as ''two state reactivity'' [51][52][53][54], which has been confirmed by experimental studies. In previous theoretical researches about CO 2 activation by Nb þ and Zr þ cations, Toscano and coworkers [2,3] have ascertained the presence of some spin inversion during the reaction process, CO 2 activation mediated by metal cations was found to be an exothermic spin-forbidden process, which resulted from a crossing between different energetic profiles.…”