Why is hafnium so unreactive?

Parke, Laura G.; Hinton, Christopher; Armentrout, P. B.

doi:10.1016/j.ijms.2006.05.025

Cited by 29 publications

(57 citation statements)

References 38 publications

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“…This agostic structure has been found to be characteristic of the early transition metals. 25,28,30,85 Geometrical parameters found here are similar to the structures reported by Di Santo et al 41 and de Almeida and Duarte, 42 who also found a 2 A′ ground state. The CH 2 wagging motion passes through the symmetric 2 A 1 state (a transition state having C 2v symmetry) lying only 0.05 eV higher in energy.…”

Section: ■ Thermochemical and Theoretical Resultssupporting

confidence: 89%

“…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%

“…The high barrier of Hf + has been ascribed to the filled 6s orbital of its 2 D (5d6s 2 ) ground state. 25 Zr + has a 4 F (4d 2 5s) ground state and does not experience the same repulsive forces because of the half-filled 5s orbital. 15 The barrier height at TS1/2 calculated using B3LYP for Th + is 18 kJ/mol, when using the similarly sized SDD basis set after accounting for spin−orbit energy.…”

Section: Inorganic Chemistrymentioning

confidence: 99%

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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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Section: ■ Thermochemical and Theoretical Resultssupporting

confidence: 89%

Section: Inorganic Chemistrymentioning

confidence: 99%

Section: Inorganic Chemistrymentioning

confidence: 99%

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

2015

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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: 87%

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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“…[3] Dagegen reagiert Hf + aus zwei Gründen nicht mit CH 4 -d ie im Grundzustand [4] doppelte Besetzung des 6s-Orbitals führt zu einer hohen Barriere für die oxidative Insertion von Hf + in eine C-H-Bindung,und eine relativ kleine Bindungsenergie BDE(Hf + -CH 2 ) = 435 kJ mol À1 macht die Reaktion endotherm. [3] Dagegen reagiert Hf + aus zwei Gründen nicht mit CH 4 -d ie im Grundzustand [4] doppelte Besetzung des 6s-Orbitals führt zu einer hohen Barriere für die oxidative Insertion von Hf + in eine C-H-Bindung,und eine relativ kleine Bindungsenergie BDE(Hf + -CH 2 ) = 435 kJ mol À1 macht die Reaktion endotherm.…”

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Thermische Aktivierung von Methan durch [HfO]^.+ und [XHfO]⁺ (X=F, Cl, Br, I): ein außergewöhnlicher Ligandeneffekt und dessen Ursache

Zhou

Schlangen

et al. 2016

Angewandte Chemie

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Die thermischen Reaktionen von Methan mit [HfO]C + und [XHfO] + (X = F, Cl, Br,I )w urden mittels FT-ICR-Massenspektrometrie und modernen quantenchemischen Rechnungen untersucht. Während [HfO]C + gegenüber Methan inert ist, ermçglichen die geschlossenschaligen Ionen [XHfO] + (X = F, Cl, Br) überraschenderweise die Aktivierung der H 3 C-H-Bindung unter Bildung des Insertionsproduktes [Hf(X)-(OH)(CH 3 )] + .M çgliche Ursachen dieses außergewçhnlichen Ligandeneffekts werden diskutiert. Die meisten Kationen der Übergangsmetalle der dritten Reihe,wie atomares Ta + ,W + ,Os + ,Ir + und Pt + ,sind aufgrund beachtlicher relativistischer Effekte [1] in der Lage,C H 4 [2]Hintergrundinformationen zu diesem Beitrag sind unter: http://dx.doi.org/10.1002/ange.201602312 zu finden.

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Why is hafnium so unreactive?

Cited by 29 publications

References 38 publications

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

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

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

Thermische Aktivierung von Methan durch [HfO]^.+ und [XHfO]⁺ (X=F, Cl, Br, I): ein außergewöhnlicher Ligandeneffekt und dessen Ursache

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Why is hafnium so unreactive?

Cited by 29 publications

References 38 publications

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

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

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

Thermische Aktivierung von Methan durch [HfO].+ und [XHfO]+ (X=F, Cl, Br, I): ein außergewöhnlicher Ligandeneffekt und dessen Ursache

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

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

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

Thermische Aktivierung von Methan durch [HfO]^.+ und [XHfO]⁺ (X=F, Cl, Br, I): ein außergewöhnlicher Ligandeneffekt und dessen Ursache