A comprehensive methodology for the study of sequential ion/molecule reactions using fourier transform ion cyclotron resonance the formation, isolation, and reactions of very large metal clusters

Forbes, Robert A.; Laukien, Frank H.; Wronka, John

doi:10.1016/0168-1176(88)80086-7

Cited by 116 publications

(57 citation statements)

References 17 publications

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“…[24,25] After transfer of the ions into the cell of a CMS 47X Fourier-transform ion-cyclotron-resonance mass spectrometer, [26] ; the latter two combinations of isotopomers are not resolved in the broadband detection-mode) was selected by means of the FERETS ion-ejection method. [27] After thermalization with pulsed-in Ar buffer gas, reactions with the leaked-in substrates were studied at variable reaction times. Bimolecular rate constants k (with estimated errors of AE 30 % for CH 4 and O 2 [28] and AE 50 % for NH 3 ) were derived from the decline of the reactant ion and the increase of the product ions on the basis of the pseudo-first-order approximation.…”

Section: Methodsmentioning

confidence: 99%

Coupling of Methane and Ammonia by Dinuclear Bimetallic Platinum–Coinage‐Metal Cations PtM⁺

2003

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The activation and functionalization of methane constitute continuing challenges for catalysis. One example of their industrial realization is given by the Degussa process for the large-scale production of hydrogen cyanide from methane and ammonia using platinum as heterogeneous catalyst [Eq. (1)].Our aim is the development of a gas-phase model for this process that may enhance the current mechanistic knowledge [1,2] and thus ultimately contribute to rational catalyst improvement. So far, atomic Pt + , homonuclear clusters Pt m + as well as small heteronuclear clusters Pt m Au n + ions have been studied. [3][4][5][6][7] Whereas all the homonuclear Pt m + clusters investigated achieve CH 4 activation in the first reaction step, [8,9] the C À N coupling of the resulting carbene species Pt m CH 2 + with NH 3 only works for m = 1. [3][4][5] In contrast, the dinuclear cluster mediates CÀN bond formation if one platinum atom is replaced by a gold atom.[6] This finding was ascribed to a particularly well-balanced binding situation in the PtAuCH 2 + species. The bonding is strong enough to afford spontaneous activation of CH 4 on the one hand but does not prevent the CH 2 fragment from coupling with NH 3 on the other.[6] Recent results have shown, however, that the larger bimetallic Pt m Au n + clusters do not mediate the coupling step between the CH 2 moiety and NH 3 , thus pointing to special features of PtAu + . [10] To further elucidate the remarkable role of the second metal in the dinuclear cluster, we have extended our studies to PtCu + and PtAg + . The change from gold to its lighter congeners copper and silver is straightforward in view of their electronic and chemical similarities (note, however, that gold is distinguished from both copper and silver by the operation of much stronger relativistic effects [11] ). As with PtAu + , the reactions with CH 4 , O 2 , and NH 3 are investigated; for comparison, the reactivities of Cu 2 + and Ag 2 + are included

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Section: Methodsmentioning

confidence: 99%

Coupling of Methane and Ammonia by Dinuclear Bimetallic Platinum–Coinage‐Metal Cations PtM⁺

2003

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“…The ions were extracted from the source, transferred into the analyzer cell by a system of electrostatic potentials and lenses, decelerated, and trapped in the field of a superconducting magnet (maximum field strength 7.05 T). Prior to ion ± molecule reactions, the 56 Fe isotope was mass-selected by using the FERETS technique, [28] a computerassisted protocol that combines frequency sweeps and single-frequency ion-ejection pulses to optimize ion isolation. FeO was generated by pulsing-in N 2 O, thermalized with pulsed-in argon, and subsequently massselected.…”

Section: Fticr-msmentioning

confidence: 99%

A Mechanistic Study of the FeO+-Mediated Decomposition Pathways of Phenol, Anisol, and Their Thio Analogues

Brönstrup

Schröder

Schwarz³

2000

Chem. Eur. J.

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The gas-phase oxidations of phenol, anisol, thiophenol, and thioanisol by 'bare' FeO+ are examined by using Fourier transform-ion cyclotron resonance (FT-ICR) and tandem mass-spectrometry. Reaction mechanisms are derived on the basis of isotope-labeling experiments, MS/MS studies, and comparison with structural isomers, that is ions formed by independent routes. The chemistry of all substrates is determined by the functional groups, whereas reactions typical of unsubstituted benzene with FeO+ are suppressed. For phenol and thiophenol, four-membered metallacycles are obtained concomitant with a regioselective loss of water, which involves the O atom from the FeO+ entity and hydrogen atoms originating from the functional group and from the ortho position of the ring. C-H bond cleavage of the methoxy group (kH/kD = 2.0) is rate-contributing for the degradation of metastable anisol/FeO+, which is featured by highly regioselective losses of H2O, HCO, H2CO, and [C,H2,O2]. In the oxidation of thioanisol, two different C-H bond activation mechanisms are operating, resulting in the elimination of [Fe,H,O,S] concomitant with the formation of the benzyl cation (kH/kD = 4.7), and loss of water (kH/kD = 2.5). The reactions of independently generated, formal S- and C-oxidation intermediates of thioanisol indicate the occurrence of extensive structural isomerizations prior to dissociation. For anisol and thioanisol, analogies and differences between oxidation reactions catalyzed by the enzyme cytochrome P-450 in the condensed phase and those observed for the gas-phase model FeO+ are discussed.

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“…Die [CuO] + -Kationen wurden durch Laserverdampfung [29] (Nd:YAG-Laser, 5 ns Laserpuls, Continuum Surelite II, 10 Hz, 5 mJ + zunächst mit der FERETS-Methode [30] massenselektiert und Methan über ein Leckventil bei konstantem Druck in der Größenordnung von 1. 5 10 À8 mbar in die Zelle geleitet.…”

Section: Experimentelles Und Methodenunclassified

Über die Rolle von [CuO]⁺ bei spinselektiven Wasserstoff‐ und Sauerstoff‐Übertragungen in der Aktivierung von Methan

et al. 2011

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Das fehlende Stück in einem fesselnden Puzzle: Mehr als zehn Jahre nach der theoretischen Vorhersage, dass kationisches [CuO]+ ein wirkungsvoller Kandidat für die Umwandlung von Methan zu Methanol sein müsste, konnte dieses Oxid in der Gasphase erzeugt werden. Eine Kombination aus Massenspektrometrie und DFT‐Rechnungen offenbart die entscheidende Rolle der Zweizustandsreaktivität sowie die Bedeutung von sauerstoffzentrierten Radikalen hinsichtlich der Selektivität in der Oxidation von Methan.

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A comprehensive methodology for the study of sequential ion/molecule reactions using fourier transform ion cyclotron resonance the formation, isolation, and reactions of very large metal clusters

Cited by 116 publications

References 17 publications

Coupling of Methane and Ammonia by Dinuclear Bimetallic Platinum–Coinage‐Metal Cations PtM⁺

Coupling of Methane and Ammonia by Dinuclear Bimetallic Platinum–Coinage‐Metal Cations PtM⁺

A Mechanistic Study of the FeO+-Mediated Decomposition Pathways of Phenol, Anisol, and Their Thio Analogues

Über die Rolle von [CuO]⁺ bei spinselektiven Wasserstoff‐ und Sauerstoff‐Übertragungen in der Aktivierung von Methan

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A comprehensive methodology for the study of sequential ion/molecule reactions using fourier transform ion cyclotron resonance the formation, isolation, and reactions of very large metal clusters

Cited by 116 publications

References 17 publications

Coupling of Methane and Ammonia by Dinuclear Bimetallic Platinum–Coinage‐Metal Cations PtM+

Coupling of Methane and Ammonia by Dinuclear Bimetallic Platinum–Coinage‐Metal Cations PtM+

A Mechanistic Study of the FeO+-Mediated Decomposition Pathways of Phenol, Anisol, and Their Thio Analogues

Über die Rolle von [CuO]+ bei spinselektiven Wasserstoff‐ und Sauerstoff‐Übertragungen in der Aktivierung von Methan

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Product

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About

Coupling of Methane and Ammonia by Dinuclear Bimetallic Platinum–Coinage‐Metal Cations PtM⁺

Coupling of Methane and Ammonia by Dinuclear Bimetallic Platinum–Coinage‐Metal Cations PtM⁺

Über die Rolle von [CuO]⁺ bei spinselektiven Wasserstoff‐ und Sauerstoff‐Übertragungen in der Aktivierung von Methan