Gas‐Phase Dehydrogenation of Methanol with Mononuclear Vanadium‐Oxide Cations

Engeser, Marianne; Schröder, Detlef; Schwarz, Helmut

doi:10.1002/chem.200401352

Cited by 58 publications

(68 citation statements)

References 74 publications

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“…[66] The B3LYP functional has been used previously for a range of vanadium oxide systems, and was shown to give reasonable agreement with available experimental data as well as with higher-level theoretical calculations. [19,20,23,24,27,31,32,[67][68][69][70] Calculations were carried out by using the 6-311 + + G** basis sets for H, C and O, and the SDD effective core potential (ECP) and associated basis sets were used for V. [71] The use of an ECP basis set for V was chosen to allow for direct comparison with the heavier Nb centres. Stationary points were characterized by frequency calculations, and unscaled zero-point energies are included for all species.…”

Section: Methodsmentioning

confidence: 99%

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Gas‐Phase Reactivity of Metavanadate [VO₃]⁻ towards Methanol and Ethanol: Experiment and Theory

Waters¹,

Wedd²,

O’Hair³

2007

Chemistry A European J

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The gas-phase reactivity of the metavanadate anion [VO3]- towards methanol and ethanol was examined by a combination of ion-molecule reaction and isotope labelling experiments in a quadrupole ion-trap mass spectrometer. The experimental data were interpreted with the aid of density functional theory calculations. [VO3]- dehydrated methanol to eliminate water and form [VO2(eta2-OCH2)]-, which features an [eta2-C,O-OCH2]2- ligand formed by formal removal of two protons from methanol and which is isoelectronic with peroxide. [VO3]- reacted with ethanol in an analogous manner to form [VO2(eta2-OCHCH3)]-, as well as by loss of ethene to form [VO2(OH)2]-. The calculations predicted that important intermediates in these reactions were the hydroxo alkoxo anions [VO2(OH)(OCH2R)]- (R: H, CH3). These were predicted to undergo intramolecular hydrogen-atom transfer to form [VO(OH)2(eta1-OCHR)]- followed by eta1-O-->eta2-C,O rearrangements to form [VO(OH)2(eta2-OCHR)]-. The latter reacted further to eliminate water and generate the product [VO2(eta2-OCHR)]-. This major product observed for [VO3]- is markedly different from that observed previously for [NbO3]- containing the heavier Group 5 congener niobium. In that case, the major product of the reaction was an ion of stoichiometry [Nb, O3, H2]- arising from the formal dehydrogenation of methanol to formaldehyde. The origin of this difference was examined theoretically and attributed to the intermediate alkoxo anion [NbO2(OH)(OCH3)]- preferring hydride transfer to form [HNbO2(OH)]- with loss of formaldehyde. This contrasts with the hydrogen-atom-transfer pathway observed for [VO2(OH)(OCH3)]-.

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Section: Methodsmentioning

confidence: 99%

“…[38,39] The majority of these gas-phase studies have been supported by theoretical calculations. [26,27,31,32,[40][41][42] We recently described the gas-phase catalytic oxidation of methanol to formaldehyde with the mononuclear metavanadate anion [VO 3 ]…”

Section: H T U N G T R E N N U N G (H 2 -Ochr)]mentioning

confidence: 99%

Gas‐Phase Reactivity of Metavanadate [VO₃]⁻ towards Methanol and Ethanol: Experiment and Theory

Waters¹,

Wedd²,

O’Hair³

2007

Chemistry A European J

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“…Proposals by Johansson et al [30] of participation of solvent molecules such as 2,2,2-trifluorethanol (TFE) in CH activation of alkyl and aryl ligands of Pt II [31,32] were challenged by Chen et al, [33,34] and this led to a discussion about the relevance of gas-phase versus solution chemistry. [35,36] The gas-phase activation of alcohols [37] is described for VO + [38] and Mn + , [39] but no gas-phase alcohol activation by Pt II is found so far. Recently Owen et al showed CH activation of alcohols by Pt II by NMR spectroscopy in solution.…”

Section: IVmentioning

confidence: 99%

The Gas‐Phase Chemistry of cis‐Diammineplatinum(II) Complexes: A Joint Experimental and Theoretical Study

Springer¹,

Bürgel²,

Böhrsch³

et al. 2006

ChemPhysChem

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Prior to reactions with DNA, the anticancer drug cisplatin [Pt(II)(NH(3))(2)Cl(2)] forms a series of solvolysis intermediates by successive replacement of the chloro ligands by water or hydroxyl groups. The bonding of water to Pt(II) is weak, and it is easily substituted by donor ligands present in the solution, for example, amines or alcohols. We studied such compounds using high-resolution electrospray mass spectrometry with a linear ion trap and DFT computations. This combination allows for the first time a detailed description of the reactions initiated by the central atom of the complexes. Positively charged cisplatin adducts with primary and secondary alcohols ([Pt(II)(NH(3))(2)(ROH)Cl](+)) show unexpected reactions when fragmented in a linear ion trap. Either water loss is accompanied by formation of the corresponding carbene complex, or loss of the corresponding aldehyde/ketone leads to the formation of the complex [Pt(NH(3))(2)(H(2))Cl](+). Complete loss of the alcohol ligand is not observed for kinetic reasons. A detailed investigation by DFT and molecular dynamics for the cisplatin/methanol complex [Pt(II)(NH(3))(2)(CH(3)OH)Cl](+) allowed identification of the reaction mechanisms leading to the observed fragmentation patterns. The initial step for both fragmentation pathways is activation of the alpha-CH bond and subsequent H transfer within the complex. Direct activation of the OH or CO bond is less favorable. Ligands bound to the Pt(II) center such as the chloro ligand can directly catalyze the reaction by intermediate binding of H atoms. Upon collision activation, adducts without an alpha-H atom such as [Pt(NH(3))(2){(CH(3))(3)COH}Cl](+) show loss of water or the corresponding alkene.

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“…[87] In [88] Interessant sind auch die theoretischen Arbeiten von Baerends und Mitarbeitern, [89] auch die berechneten Energiebarrieren von einer ¾nderung in der Mikroumgebung der Cluster stark beeinflusst. [89] Eine bemerkenswerte Metallabhängigkeit der konkurrierenden Aktivierung von C-H-und O-H-Bindungen von Methanol wurde auch bei der Elektrospray-Ionisierung von methanolischen Lçsungen von MX 2 (M = Fe, Co, Ni; X = Br, I) beobachtet.…”

Section: Der Erste Schritt: Spaltung Der Starken O-h-oder Der Schwächunclassified

Chemie mit Methan: Studieren geht über Probieren!

Schwarz

2011

Angewandte Chemie

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170

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Konzeptionelle Überlegungen zu und mechanistische Aspekte von vier scheinbar einfachen chemischen Umsetzungen, die in der Chemie von Methan von Bedeutung sind, werden in diesem Aufsatz behandelt: 1) die metallvermittelte Dehydrierung unter Bildung von Metallcarbenkomplexen, 2) die Wasserstoffabstraktion als Schlüsselschritt der oxidativen Dimerisierung von Methan, 3) der Mechanismus der CH4→CH3OH‐Umwandlung, und 4) die Reihenfolge der C‐H‐ und O‐H‐Bindungsaktivierung und die Frage nach dem geschwindigkeitsbestimmenden Schritt in der selektiven Oxidation von Methanol zu Formaldehyd. Moderne Gasphasenexperimente, in Verbindung mit Elektronenstrukturrechnungen, liefern Einblicke in elementare Reaktionsschritte auf molekularer Ebene und enthüllen reaktionsmechanistische Details. Die Ergebnisse dieser Untersuchungen werden, wo dies angebracht erscheint, mit Beobachtungen aus entsprechenden Studien in Lösung oder auf Oberflächen verglichen.

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Gas‐Phase Dehydrogenation of Methanol with Mononuclear Vanadium‐Oxide Cations

Cited by 58 publications

References 74 publications

Gas‐Phase Reactivity of Metavanadate [VO₃]⁻ towards Methanol and Ethanol: Experiment and Theory

Gas‐Phase Reactivity of Metavanadate [VO₃]⁻ towards Methanol and Ethanol: Experiment and Theory

The Gas‐Phase Chemistry of cis‐Diammineplatinum(II) Complexes: A Joint Experimental and Theoretical Study

Chemie mit Methan: Studieren geht über Probieren!

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Gas‐Phase Dehydrogenation of Methanol with Mononuclear Vanadium‐Oxide Cations

Cited by 58 publications

References 74 publications

Gas‐Phase Reactivity of Metavanadate [VO3]− towards Methanol and Ethanol: Experiment and Theory

Gas‐Phase Reactivity of Metavanadate [VO3]− towards Methanol and Ethanol: Experiment and Theory

The Gas‐Phase Chemistry of cis‐Diammineplatinum(II) Complexes: A Joint Experimental and Theoretical Study

Chemie mit Methan: Studieren geht über Probieren!

Contact Info

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Gas‐Phase Reactivity of Metavanadate [VO₃]⁻ towards Methanol and Ethanol: Experiment and Theory

Gas‐Phase Reactivity of Metavanadate [VO₃]⁻ towards Methanol and Ethanol: Experiment and Theory