The Dynamics of the Reaction of FeO<sup>+</sup> and H<sub>2</sub>: A Model for Inorganic Oxidation

Essafi, Stéphanie; Tew, David P.; Harvey, Jeremy N.

doi:10.1002/ange.201702009

Cited by 16 publications

(7 citation statements)

References 26 publications

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“…This interplay between sextet and quartet surfaces has been observed in reactions of FeO + with both H 2 and CH 4 . ,, Interestingly, in both cases it was determined that the initial crossing behaves adiabatically, having little kinetic effect. The second crossing was found to have both adiabatic (spin-crossing) and diabatic (spin-conserving) components leading to production of both ground and excited state products. , In the present experiments at thermal energies, any diabatic component is significantly hindered energetically and thus likely to lower reaction efficiency as the complex dissociates back to reactants. Armentrout has observed an increase in diabatic behavior with increased translational energy for several systems. , If that were the case here, the increased reactivity with increasing energy would be mitigated by the increased diabaticity of the spin crossings, manifesting as apparent activation energies smaller than expected from Arrhenius behavior with a known endothermic barrier, such as observed here.…”

Section: Resultsmentioning

confidence: 52%

Kinetics of First-Row Transition Metal Cations (V⁺, Fe⁺, Co⁺) with OCS at Thermal Energies

et al. 2018

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The temperature-dependent kinetics for reactions of V, Fe, and Co with OCS are measured using a selected ion flow tube apparatus heated to 300-600 K. All three reactions proceed solely by C-S activation at thermal energies, resulting in metal sulfide cation formation. Previously calculated reaction pathways were employed to inform statistical modeling of these reactions for comparison to the data. As surmised previously, all three reactions at thermal energies require spin crossing, with the Fe reaction crossing once circumventing a prohibitive transition state, before crossing again to form ground state products. The Fe and Co reaction efficiencies increase with energy. For the Co reaction, and to a lesser extent the Fe reaction, the apparent activation energies are less than the reaction endothermicities, possibly indicating increasing diabatic behavior of the spin crossings with energy. The V reaction was well modeled assuming an entirely adiabatic spin crossing, such that the resultant avoided crossing behaves similarly to a tight transition state. The subsequent reaction of VS with OCS producing VS is also investigated; the rate-limiting transition state energy derived from statistical modeling is poorly reproduced by quantum calculations using a variety of methods, highlighting the large (1-2 eV) uncertainty in calculated energetics of transition-metal containing species.

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Section: Resultsmentioning

confidence: 52%

Kinetics of First-Row Transition Metal Cations (V⁺, Fe⁺, Co⁺) with OCS at Thermal Energies

et al. 2018

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“… a Multiplicity indicated in parentheses where relevant b Reference CCSD(T)/aug-cc-PV(T,Q)Z//B3LYP/6-311++G(d,p). c Reference BP86. d Reference . Diffusion Monte Carlo (DMC). e Reference .…”

Section: Statistical Modeling Of Ion–molecule Reactionsmentioning

confidence: 99%

Old School Techniques with Modern Capabilities: Kinetics Determination of Dynamical Information Such as Barriers, Multiple Entrance Channel Complexes, Product States, Spin Crossings, and Size Effects in Metallic Ion–Molecule Reactions

2021

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We show how the powerful combination of temperature-dependent kinetics coupled with detailed statistical modeling can be used to derive dynamical information about transition state barrier heights, the importance of multiple entrance channel complexes, crossings between spin surfaces, energetics, product states, and other information for metal-ion reactions. The methods are not new, but with improved computers, ion sources, ion transport, and better detection techniques, the ability to derive such parameters from the combination of methods has improved greatly. Temperature-dependent kinetics is very sensitive to the above list of parameters because the energy is varied in a controlled way that can be easily modeled. The present measurements, performed in our variable-ion source temperature-adjustable selected-ion flow tube (VISTA-SIFT), have been enabled by advances in ion transport and injection improvements so that dim sources can be used. Replacing the quadrupole mass spectrometer detector with a time-of-flight mass spectrometer solved additional problems. Quantum chemical calculations have improved greatly and provide details about the surfaces, as well as frequencies, to use as starting points for the statistical modeling. For ion–molecule reactions, incorporation of both energy and angular momentum effects are important and we have developed an in-house computer program, based on the work of Juergen Troe, to rapidly compare statistical modeling predictions to the experimental data. As we show, modeling the kinetics data can often determine the most important parameters controlling the reactivity and deriving them is much simpler and usually more accurate than detailed ab initio calculations or dynamical modeling. Additionally, we show that even without statistical modeling, temperature-dependent rate constants as a function of metal anion cluster size can be used to show that such species react by the same mechanism as surfaces. In this review, we discuss reactions of metallic atomic ions, small metal oxide ions, mixed metal oxide ions, and a series of metallic anionic cluster reactions with small molecules such as CO, O2, CO2, N2O, CH4, and several other species. Particular attention was paid to reactions involving bond activation pertinent to catalysis.

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“…One such mechanism pervasive in many transition metal mediated reactions, including the title reaction, is the role of multiple spin states in enhancing reactivity . Numerous transition metal mediated reactions have been shown to be facilitated by the reaction complex changing spin state along the reaction coordinate, as evidenced by the observation of spin-forbidden products, or by the circumvention of inhibitive barriers at thermal energies. − Quantitative evaluation of this spin crossing is daunting, as it requires significant calculation of the multidimensional potential surface in the vicinity of the crossing. − Qualitative assessments, typically based on spin–orbit coupling ⟨SOC⟩, have been shown to be at times misleading . The reaction of NiO + + CH 4 offers a system with which to probe spin crossing, as the spin allowed reaction is not accessible at thermal energies.…”

Section: Introductionmentioning

confidence: 99%

Temperature and Isotope Dependent Kinetics of Nickel-Catalyzed Oxidation of Methane by Ozone

et al. 2018

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The temperature dependent kinetics of Ni + O and of NiO + CH/CD are measured from 300 to 600 K using a selected-ion flow tube apparatus. Together, these reactions comprise a catalytic cycle converting CH to CHOH. The reaction of Ni + O proceeds at the collisional limit, faster than previously reported at 300 K. The NiO product reacts further with O, also at the collisional limit, yielding both higher oxides (up to NiO is observed) as well as undergoing an apparent reduction back to Ni. This apparent reduction channel is due to the oxidation channel yielding NiO* with sufficient energy to dissociate. NiO + CH (CD) (whereas NiO refers to the quartet state of NiO) proceeds with a rate constant of (2.6 ± 0.4) × 10 cm s [(1.8 ± 0.5) × 10 cm s] at 300 K and a temperature dependence of ∼ T (∼ T), producing only the Ni + CHOH channel up to 600 K. Statistical modeling of the reaction based on calculated stationary points along the reaction coordinate reproduces the experimental rate constant as a function of temperature but underpredicts the kinetic isotope shift. The modeling was found to better represent the data when the crossing from quartet to doublet surface was incomplete, suggesting a possible kinetic effect in crossing from quartet to doublet surfaces. Additionally, the modeling predicts a competing NiOH + CH channel to become increasingly important at higher temperatures.

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The Dynamics of the Reaction of FeO⁺ and H₂: A Model for Inorganic Oxidation

Cited by 16 publications

References 26 publications

Kinetics of First-Row Transition Metal Cations (V⁺, Fe⁺, Co⁺) with OCS at Thermal Energies

Kinetics of First-Row Transition Metal Cations (V⁺, Fe⁺, Co⁺) with OCS at Thermal Energies

Old School Techniques with Modern Capabilities: Kinetics Determination of Dynamical Information Such as Barriers, Multiple Entrance Channel Complexes, Product States, Spin Crossings, and Size Effects in Metallic Ion–Molecule Reactions

Temperature and Isotope Dependent Kinetics of Nickel-Catalyzed Oxidation of Methane by Ozone

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The Dynamics of the Reaction of FeO+ and H2: A Model for Inorganic Oxidation

Cited by 16 publications

References 26 publications

Kinetics of First-Row Transition Metal Cations (V+, Fe+, Co+) with OCS at Thermal Energies

Kinetics of First-Row Transition Metal Cations (V+, Fe+, Co+) with OCS at Thermal Energies

Old School Techniques with Modern Capabilities: Kinetics Determination of Dynamical Information Such as Barriers, Multiple Entrance Channel Complexes, Product States, Spin Crossings, and Size Effects in Metallic Ion–Molecule Reactions

Temperature and Isotope Dependent Kinetics of Nickel-Catalyzed Oxidation of Methane by Ozone

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The Dynamics of the Reaction of FeO⁺ and H₂: A Model for Inorganic Oxidation

Kinetics of First-Row Transition Metal Cations (V⁺, Fe⁺, Co⁺) with OCS at Thermal Energies

Kinetics of First-Row Transition Metal Cations (V⁺, Fe⁺, Co⁺) with OCS at Thermal Energies