Electronic structure considerations for methane activation by third-row transition-metal ions

Irikura, Karl K.; Beauchamp, J. L.

doi:10.1021/j100174a057

Cited by 268 publications

(318 citation statements)

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“…There is better agreement on the higher-order chemistry as both experiments show further reaction of HfO + to form HfO 2 H + (HfO 2 D + ) and then its hydrate, but our rate coefficient of 6.4 × 10 -10 cm 3 molecule -1 s -1 for the reaction of HfO + is again larger than that of 1.6 × 10 -10 cm 3 molecule -1 s -1 reported by Beauchamp and Irikura. 30 Figure 5 displays the dependence of the efficiency of O-atom transfer on the known O-atom affinity of the metal cation. It is interesting to note in Figure 5 Apparently, the rates of these reactions are constrained by the change in spin required to proceed from the reactant to the product potential energy surfaces, as has been proposed previously by Armentrout et al 10,18 for the reactions of Sc + , Ti + , and V + .…”

Section: Sixth-row Atomicmentioning

confidence: 99%

Heavy Water Reactions with Atomic Transition-Metal and Main-Group Cations: Gas Phase Room-Temperature Kinetics and Periodicities in Reactivity

2007

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Reactions of heavy water, D 2 O, have been measured with 46 atomic metal cations at room temperature in a helium bath gas at 0.35 Torr using an inductively coupled plasma/selected ion flow tube tandem mass spectrometer. The atomic cations were produced at ca. 5500 K in an ICP source and were allowed to decay radiatively and thermalize by collisions with Ar and He atoms prior to reaction. Rate coefficients and product distributions are reported for the reactions of fourth-row atomic cations from K + to Se + , of fifth-row atomic cations from Rb + to Te + (excluding Tc + ), and of sixth-row atomic cations from Cs + to Bi + . Primary reaction channels were observed leading to O-atom transfer, OD transfer, and D 2 O addition. O-Atom transfer occurs almost exclusively (g90%) in the reactions with most early transition-metal cations (Sc + , Ti

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Section: Sixth-row Atomicmentioning

confidence: 99%

Heavy Water Reactions with Atomic Transition-Metal and Main-Group Cations: Gas Phase Room-Temperature Kinetics and Periodicities in Reactivity

2007

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“…There is a growing body of experimental information regarding the interactions of small neutral 1 and cationic [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] clusters of transition metals with compounds containing prototypical bonds ͑e.g., C-H, C-C, N-H, O-H, Si-H, Si-C͒ of importance in catalytic processes. Transition metal-main group complexes have been the focus of intense computational effort.…”

Section: Introductionmentioning

confidence: 99%

“…Blomberg and co-workers 56 performed complete active space self-consistent field ͑CASSCF͒ plus CI calculations on the reactions of Fe, Co, Ni, Rh, and Pd with CH 4 and C 2 H 6 , and concluded that the second row transition metals have higher barriers to insertion than do their first row analogs. Gordon and co-workers 60 have examined the PES's for reaction of Co ϩ with CH 4 , while Morokuma et al 61 have performed the analogous calculations for Rh In this paper, we study the reaction mechanism of Co ϩ ϩNH 3 , as a prototype for N-H bond activation by transition metal ions. For this reaction, Clemmer and Armentrout 2 proposed the following mechanism based on experimental analyses using guided ion beam mass spectrometry.…”

Section: Introductionmentioning

confidence: 99%

An ab initio study of the reaction mechanism of Co++NH3

Taketsugu

Gordon

1997

The Journal of Chemical Physics

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To investigate the mechanism for N-H bond activation by a transition metal, the reactions of Co+(3F,5F) with NH3 have been studied with complete active space self-consistent field (CASSCF), multireference configuration interaction (MR-SDCI), and multireference many body perturbation theory (MRMP) wave functions, using both effective core potential and all-electron methods. Upon their initial approach, the reactants yield an ion-molecule complex, CoNH+3(3E,5A2,5A1), with retention of C3ν symmetry. The Co+=NH3 binding energies are estimated to be 49 (triplet) and 45 (quintet) kcal/mol. Subsequently, the N-H bond is activated, leading to an intermediate complex H-Co-NH+2 (C2ν symmetry), through a threecenter transition state with an energy barrier of 56-60 (triplet) and 70-73 (quintet) kcal/mol. The energy of H-Co-NH+2, relative to that of CoNH+3, is estimated to be 60 to 61 (triplet) and 44 (quintet) kcal/mol. However, the highest levels of theory employed here (including dynamic correlation corrections) suggest that the triplet intermediate HCoNH+2 may not exist as a minimum on the potential energy surface. Following Co-N or H-Co bond cleavage, the complexH-Co-NH+2 leads to HCo++NH2 or H+CoNH+2. Both channels (triplet and quintet) are found to be endothermic by 54-64 kcal/mol. Theoretical study of the water activation by a cobalt cation: Ab initio multireference theory versus density functional theory

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“…Heterolysis of a C-H bond by either deprotonation (route a in Scheme 1) or hydride transfer (route b in Scheme 1) leads to methyl anion and cation, respectively, concomitant with the corresponding metal-hydride fragments. C-H bond homolysis, usually occurring as H-atom abstraction (route c in Scheme 1), leads to the production of a methyl radical, which constitutes the first step in the oxidative coupling of methane to ethane via recombination of two CH 3 • radicals. Transition metals capable to easily change their valence state are also able to undergo oxidative insertion into the C-H bond (route d in Scheme 1).…”

mentioning

confidence: 99%

“…A landmark discovery was made by Irikura and Beauchamp (2,3), who detected thermal reactions of methane with 5d transitionmetal cations; Reaction 1 with M ϭ Ta, W, Os, Ir, and Pt.…”

mentioning

confidence: 99%

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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Electronic structure considerations for methane activation by third-row transition-metal ions

Cited by 268 publications

References 0 publications

Heavy Water Reactions with Atomic Transition-Metal and Main-Group Cations: Gas Phase Room-Temperature Kinetics and Periodicities in Reactivity

Heavy Water Reactions with Atomic Transition-Metal and Main-Group Cations: Gas Phase Room-Temperature Kinetics and Periodicities in Reactivity

An ab initio study of the reaction mechanism of Co++NH3

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

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