Hydrido methylidene, hydrido vinylidene, hydrido oxo, and hydrido formaldehyde derivatives of bis(pentamethylcyclopentadienyl)tantalum

Asselt, A. Van; Burger, Barbara J.; Gibson, Vernon C.; Bercaw, John E.

doi:10.1021/ja00277a051

Cited by 144 publications

(77 citation statements)

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“…Common routes to alkenyl complexes: (A) RCϵCR; [2,3] (B) Nu -, nucleophile is β to metal; [4] (C) E + , electrophile is β to metal; [5] (D) Nu -, nucleophile is α to metal; [6] (E) rearrangement yields alkenyl; [7] (F) H 2 C=C(X)R, X = halide; [8] (G) loss of H + to produce α-alkoxyalkenyls. [9] groups exploring the effect of polydentate donors on the structure and reactivity of alkenyl complexes.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic, Structural and Theoretical Investigation of Alkenyl Ruthenium Complexes Supported by Sulfur–Nitrogen Mixed‐Donor Ligands

et al. 2006

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Section: Introductionmentioning

confidence: 99%

Spectroscopic, Structural and Theoretical Investigation of Alkenyl Ruthenium Complexes Supported by Sulfur–Nitrogen Mixed‐Donor Ligands

et al. 2006

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“…[54] For example, the complex Cp 2 V(h 2 -O,C-OCH 2 ) (Cp: h 5 -C 5 H 5 ) was prepared by reaction of paraformaldehyde with vanadocene Cp 2 V. [55,56] Equivalent ligands have been observed for the heavier congeners niobium and tantalum, [57,58] as well as for siloxide-supported centres, for example, [(tBu 3 SiO) 3 Ta(h 2 -O,C-OCH 2 )]. [59][60][61] Such complexes are relevant to the catalytic reduction of carbon monoxide, for which coordinated h 2 -O,C-OCH 2 ligands are possible intermediates.…”

Section: )]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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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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“…Recent studies of propane metathesis in a continuous flow reactor showed by varying the contact time, that olefins and hydrogen were primary products of this reaction. On the basis of the product selectivities and the properties of tantalum complexes to undergo a-H [8,9] or b-H [9,10] transfer processes, it was then inferred [11,12] that alkane metathesis should involve the same carbene and metallacyclobutane intermediates as olefin metathesis [13]. Thus the reaction is believed to begin by the C-H bond activation of the alkane by the tantalum hydride leading to a surface tantalum alkyl complex [4,14,15]; a carbene hydride and an olefin hydride species can then result from a-H and b-H abstractions on this complex; classically, the interaction of the carbene and the olefin can lead to a tantallacyclobutane [16,17] which by decomposition will afford a new carbene and a new olefin; hydrogenation of these latter produces the new alkanes.…”

Section: Introductionmentioning

confidence: 99%

Alumina supported tungsten hydrides, new efficient catalysts for alkane metathesis

et al. 2006

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Silica and alumina supported tantalum and tungsten hydrides were tested in alkane metathesis, for comparison of their catalytic properties. In propane metathesis [W]-H/Al 2 O 3 proves to be twice more efficient than the usual [Ta]-H/SiO 2 catalyst which is still better than [Ta]-H/Al 2 O 3 and [W]-H/SiO 2 . Tungsten based catalysts lead to a narrower distribution in the products selectivity and to a higher amount of linear products than [Ta]-H/SiO 2 . [W]-H/Al 2 O 3 is also a better catalyst than [Ta]-H/SiO 2 for butane metathesis but is less efficient with ethane. Whereas the results in the case of propane or butane can involve the higher initial activity and a lower deactivation of the tungsten catalyst, in the case of ethane, mechanistic or kinetic aspects can be envisaged in particular concerning the difficulty to dehydrogenate ethane into ethylene.

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Hydrido methylidene, hydrido vinylidene, hydrido oxo, and hydrido formaldehyde derivatives of bis(pentamethylcyclopentadienyl)tantalum

Cited by 144 publications

References 1 publication

Spectroscopic, Structural and Theoretical Investigation of Alkenyl Ruthenium Complexes Supported by Sulfur–Nitrogen Mixed‐Donor Ligands

Spectroscopic, Structural and Theoretical Investigation of Alkenyl Ruthenium Complexes Supported by Sulfur–Nitrogen Mixed‐Donor Ligands

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

Alumina supported tungsten hydrides, new efficient catalysts for alkane metathesis

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Hydrido methylidene, hydrido vinylidene, hydrido oxo, and hydrido formaldehyde derivatives of bis(pentamethylcyclopentadienyl)tantalum

Cited by 144 publications

References 1 publication

Spectroscopic, Structural and Theoretical Investigation of Alkenyl Ruthenium Complexes Supported by Sulfur–Nitrogen Mixed‐Donor Ligands

Spectroscopic, Structural and Theoretical Investigation of Alkenyl Ruthenium Complexes Supported by Sulfur–Nitrogen Mixed‐Donor Ligands

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

Alumina supported tungsten hydrides, new efficient catalysts for alkane metathesis

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