The most reactive third-row transition metal: Guided ion beam and theoretical studies of the activation of methane by Ir+

Li, Feng Xia; Zhang, Xiao Guang; Armentrout, P. B.

doi:10.1016/j.ijms.2006.02.021

Cited by 76 publications

(82 citation statements)

References 72 publications

(185 reference statements)

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“…This pathway is also the lowest energy channel for the third-row transition metal ions, Hf + and Ta + . 34,36 For other third-row transition metal ions, W + , 32 Re + , 31 Ir + , 57 and Pt + , 30 a different reaction mechanism involving a dihydride methylene intermediate has been confirmed by calculations. )TaCH 2 2+ ( 4 A′′), which easily loses dihydrogen to form TaCH 2 2+ ( 4 B 2 ) + H 2 products.…”

Section: Discussionmentioning

confidence: 88%

Energetics and Mechanisms of C−H Bond Activation by a Doubly Charged Metal Ion: Guided Ion Beam and Theoretical Studies of Ta²⁺+ CH₄

2008

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A guided ion beam tandem mass spectrometer is used to study the kinetic-energy dependence of doubly charged atomic tantalum cations (Ta(2+)) reacting with CH4 and CD4. As for the analogous singly charged system, the dehydrogenation reaction to form TaCH2(2+) + H2 is exothermic. The charge-transfer reaction to form Ta(+) + CH4(+) and the charge-separation reaction to form TaH(+) + CH3(+) are also observed at low energies in exothermic processes, as is a secondary reaction of TaCH2(2+) to form TaCH3(+) + CH3(+). At higher energies, other doubly charged products, TaC(2+) and TaCH3(2+), are observed, although no formation of TaH(2+) was observed. Modeling of the endothermic cross sections provides 0 K bond dissociation energies (in electronvolts) of D0(Ta(2+)-C) = 5.42 +/- 0.19 and D0(Ta(2+)-CH3) = 3.40 +/- 0.16. These experimental bond energies are in poor agreement with density functional calculations at the B3LYP/HW+/6-311++G(3df,3p) level of theory. However, the Ta(2+)-C bond energy is in good agreement with calculations at the QCISD(T) level of theory, and the Ta(2+)-CH3 bond energy is in good agreement with density functional calculations at the BHLYP level of theory. Theoretical calculations reveal the geometric and electronic structures of all product ions and are used to map the potential energy surface, which describes the mechanism of the reaction and key intermediates. Both experimental and theoretical results suggest that TaH(+), TaCH2(2+), and TaCH3(2+) are formed through a H-Ta(2+)-CH3 intermediate.

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Section: Discussionmentioning

confidence: 88%

Energetics and Mechanisms of C−H Bond Activation by a Doubly Charged Metal Ion: Guided Ion Beam and Theoretical Studies of Ta²⁺+ CH₄

2008

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“…22,23,25,27,28,30,53,69,70,86 In all cases, the difference is attributed to competition with the formation of the metal carbene because of a shared, common intermediate. Because reactions of M + with H 2 produce only one product, no competition exists that may delay the onset of reaction.…”

Section: Inorganic Chemistrymentioning

confidence: 99%

“…Thus, the relative BDEs are Ti + ≈ Hf + < Zr + ≈ Th + . Typically, BDEs increase moving down the periodic table because of the lanthanide contraction, 22,23,26,27,89 leading to an expected trend in BDEs of Ti + < Zr + < Hf + < Th + . The lower BDEs of Hf + ( 2 D, 5d6s 2 ) have previously been explained by the filled 6s orbital, which inhibits bond formation, 25 compared to the open d-shell configurations of Ti + ( 4 F, 3d 2 4s) and Zr + ( 4 F, 4d 2 5s).…”

Section: Inorganic Chemistrymentioning

confidence: 99%

Activation of CH₄ by Th⁺ as Studied by Guided Ion Beam Mass Spectrometry and Quantum Chemistry

2015

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The reaction of atomic thorium cations with CH4 (CD4) and the collision-induced dissociation (CID) of ThCH4(+) with Xe are studied using guided ion beam tandem mass spectrometry. In the methane reactions at low energies, ThCH2(+) (ThCD2(+)) is the only product; however, the energy dependence of the cross-section is inconsistent with a barrierless exothermic reaction as previously assumed on the basis of ion cyclotron resonance mass spectrometry results. The dominant product at higher energies is ThH(+) (ThD(+)), with ThCH3(+) (ThCD3(+)) having a similar threshold energy. The latter product subsequently decomposes at still higher energies to ThCH(+) (ThCD(+)). CID of ThCH4(+) yields atomic Th(+) as the exclusive product. The cross-sections of all product ions are modeled to provide 0 K bond dissociation energies (in eV) of D0(Th(+)-H) ≥ 2.25 ± 0.18, D0(Th(+)-CH) = 6.19 ± 0.16, D0(Th(+)-CH2) ≥ 4.54 ± 0.09, D0(Th(+)-CH3) = 2.60 ± 0.30, and D0(Th(+)-CH4) = 0.47 ± 0.05. Quantum chemical calculations at several levels of theory are used to explore the potential energy surfaces for activation of methane by Th(+), and the effects of spin-orbit coupling are carefully considered. When spin-orbit coupling is explicitly considered, a barrier for C-H bond activation that is consistent with the threshold measured for ThCH2(+) formation (0.17 ± 0.02 eV) is found at all levels of theory, whereas this barrier is observed only at the BHLYP and CCSD(T) levels otherwise. The observation that the CID of the ThCH4(+) complex produces Th(+) as the only product with a threshold of 0.47 eV indicates that this species has a Th(+)(CH4) structure, which is also consistent with a barrier for C-H bond activation. This barrier is thought to exist as a result of the mixed ((4)F,(2)D) electronic character of the Th(+) J = (3)/2 ground level combined with extensive spin-orbit effects.

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“…Ir (16), and Au (17). Several metal dications were also found to activate methane in analogy to Reaction 1 (18).…”

mentioning

confidence: 93%

Gas-phase activation of methane by ligated transition-metal cations

Schröder

Schwarz²

2008

Proc. Natl. Acad. Sci. U.S.A.

237

135

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Motivated by the search for ways of a more efficient usage of the large, unexploited resources of methane, recent progress in the gas-phase activation of methane by ligated transition-metal ions is discussed. Mass spectrometric experiments demonstrate that the ligands can crucially influence both reactivity and selectivity of transition-metal cations in bond-activation processes, and the most reactive species derive from combinations of transition metals with the electronegative elements fluorine, oxygen, and chlorine. Furthermore, the collected knowledge about intramolecular kinetic isotope effects associated with the activation of C-H(D) bonds of methane can be used to distinguish the nature of the bond activation as a mere hydrogen-abstraction, a metal-assisted mechanism or more complex reactions such as formation of insertion intermediates or -bond metathesis.bond activation ͉ kinetic isotope effects ͉ mass spectrometry

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The most reactive third-row transition metal: Guided ion beam and theoretical studies of the activation of methane by Ir+

Cited by 76 publications

References 72 publications

Energetics and Mechanisms of C−H Bond Activation by a Doubly Charged Metal Ion: Guided Ion Beam and Theoretical Studies of Ta²⁺+ CH₄

Energetics and Mechanisms of C−H Bond Activation by a Doubly Charged Metal Ion: Guided Ion Beam and Theoretical Studies of Ta²⁺+ CH₄

Activation of CH₄ by Th⁺ as Studied by Guided Ion Beam Mass Spectrometry and Quantum Chemistry

Gas-phase activation of methane by ligated transition-metal cations

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The most reactive third-row transition metal: Guided ion beam and theoretical studies of the activation of methane by Ir+

Cited by 76 publications

References 72 publications

Energetics and Mechanisms of C−H Bond Activation by a Doubly Charged Metal Ion: Guided Ion Beam and Theoretical Studies of Ta2++ CH4

Energetics and Mechanisms of C−H Bond Activation by a Doubly Charged Metal Ion: Guided Ion Beam and Theoretical Studies of Ta2++ CH4

Activation of CH4 by Th+ as Studied by Guided Ion Beam Mass Spectrometry and Quantum Chemistry

Gas-phase activation of methane by ligated transition-metal cations

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Energetics and Mechanisms of C−H Bond Activation by a Doubly Charged Metal Ion: Guided Ion Beam and Theoretical Studies of Ta²⁺+ CH₄

Energetics and Mechanisms of C−H Bond Activation by a Doubly Charged Metal Ion: Guided Ion Beam and Theoretical Studies of Ta²⁺+ CH₄

Activation of CH₄ by Th⁺ as Studied by Guided Ion Beam Mass Spectrometry and Quantum Chemistry