Studies on transition metal peroxo complexes. Part 8. The nature of peroxomolybdates and peroxotungstates in aqueous solution

Campbell, N. J.; Dengel, Andrew C.; Edwards, Catherine J.; Griffith, William P.

doi:10.1039/dt9890001203

Cited by 147 publications

(80 citation statements)

References 3 publications

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“…2-predominates at pH # 5 [4,31,32]. Thus in the present study, the strategically maintained pH of ca.…”

Section: Discussionmentioning

confidence: 92%

“…Tungsten has strong affinity for peroxide and the composition of peroxo-tungsten species has been known to be sensitive to pH [4,31,32]. In a solution of tungstate and excess H 2 O 2 at a pH $ 5 diperoxotungstate species is readily formed, whereas the dimeric species, […”

Section: Discussionmentioning

confidence: 99%

“…530 cm 21 , respectively. The spectra enabled clear identification of n(WvO) near 960 cm 21 arising from terminally bonded WvO group [31,32].…”

Section: Synthesis and Characterizationmentioning

confidence: 99%

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Mononuclear and dinuclear peroxotungsten complexes with co-ordinated dipeptides as potent inhibitors of alkaline phosphatase activity

Hazarika

Kalita

Islam

2008

Journal of Enzyme Inhibition and Medicinal Chemistry

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New molecular peroxotungstate(VI) complexes with dipeptides as ancillary ligands of the type, [WO(O 2 ) 2 (dipeptide) (H 2 O)].3H 2 O, dipeptide ¼ glycyl-glycine or glycyl-leucine, have been synthesized and characterized by elemental analysis, spectral and physico-chemical methods including thermal analysis. The complexes contain side-on bound peroxo groups and a peptide zwitterion bonded to the metal centre unidentately through an O(carboxylate) atom. Investigations on certain biologically important key properties of these compounds and a set of dimeric compounds in analogous co-ligand environment, Na 2 [W 2 O 3 (O 2 ) 4 (dipeptide) 2 ].3H 2 O, dipeptide ¼ glycyl-glycine and glycyl-leucine, reported previously by us revealed interesting features of the compounds. Each of the compounds despite having a 7 co-ordinated metal centre exerts a strong inhibitory effect on alkaline phosphatase activity with a potency higher than that of the free dipeptide, tungstate or peroxotungstate. The compounds exhibit remarkable stability in solutions of acidic as well as physiological pH and are weaker as substrate to the enzyme catalase, compared to H 2 O 2 . The mononuclear and dinuclear peroxotungsten compounds are efficient oxidants of reduced glutathione (GSH), a reaction in which only one of the peroxo groups of a diperoxotungsten moiety of the complexes was found to be active.

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“…2-predominates at pH # 5 [4,31,32]. Thus in the present study, the strategically maintained pH of ca.…”

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

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Mononuclear and dinuclear peroxotungsten complexes with co-ordinated dipeptides as potent inhibitors of alkaline phosphatase activity

Hazarika

Kalita

Islam

2008

Journal of Enzyme Inhibition and Medicinal Chemistry

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“…Molecular structure of the anion part of I is depicted in Figure 1. The method [45] for the preparation of the tetrahexylammonium derivative of [{W(=O)(O 2 ) 2 Allylic alcohols 7 a, 9 a, and 10 a were synthesized and confirmed by GC analysis in combination with mass and 1 H and 13 C NMR spectroscopy as reported previously. [46][47][48][49] All epoxy alcohols are known and have been identified by comparison of their 1 H and 13 C NMR signals with the literature data.…”

Section: Methodsmentioning

confidence: 99%

Highly Selective, Recyclable Epoxidation of Allylic Alcohols with Hydrogen Peroxide in Water Catalyzed by Dinuclear Peroxotungstate

Kamata

Yamaguchi

Mizuno

2004

Chemistry A European J

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The highly chemo-, regio-, and diastereoselective and stereospecific epoxidation of various allylic alcohols with only one equivalent of hydrogen peroxide in water can be efficiently catalyzed by the dinuclear peroxotungstate, K2[[W(=O)(O2)2(H2O)]2(mu-O)].2H2O (I). The catalyst is easily recycled while maintaining its catalytic performance. The catalytic reaction mechanism including the exchange of the water ligand to form the tungsten-alcoholate species followed by the insertion of oxygen to the carbon-carbon double bond, and the regeneration of the dinuclear peroxotungstate with hydrogen peroxide is proposed. The reaction rate shows first-order dependence on the concentrations of allylic alcohol and dinuclear peroxotungstate and zero-order dependence on the concentration of hydrogen peroxide. These results, the kinetic data, the comparison of the catalytic rates with those for the stoichiometric reactions, and kinetic isotope effects indicate that the oxygen transfer from a dinuclear peroxotungstate to the double bond is the rate-limiting step for terminal allylic alcohols such as 2-propen-1-ol (1a).

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“…[4,6] However, this picture was later modified and refined by coupling kinetic data and spectroscopic experiments. Whereas Raman, IR, and UV/Vis spectroscopy failed to distinguish unequivocally among the various peroxomolybdates, [7,8] several peroxomolybdates (such as mono-, di-, tri-, and tetraperoxomolybdate) were identified unambiguously by 95 Mo NMR spectroscopy. [9] Comparison of the 95 4 2À do not contribute significantly to the formation of 1 O 2 .…”

Section: Introductionmentioning

confidence: 99%

Kinetic and Spectroscopic Study of¹O₂Generation from H₂O₂Catalyzed by LDH–MoO₄²⁻(LDH=Layered Double Hydroxide)

Sels

Vos

Grobet

et al. 2001

Chemistry A European J

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Layered double hydroxides (LDHs), exchanged with molybdate, decompose H2O2 to form one molecule of singlet-state dioxygen (1O2) from two molecules of H2O2. The dependence of the kinetics of H2O2 decomposition on Mo and H2O2 concentrations and on temperature has been related to structural characteristics of the material (X-ray diffraction (XRD), scanning electron microscopy (SEM), IR spectroscopy, N2 adsorption, thermogravimetry) and to molybdate speciation as revealed by in-situ studies in the presence of peroxide (FT Raman, diffuse reflectance UV/visible spectroscopy). The H2O2 decomposition rate is linearly correlated with the amount of LDH-exchanged molybdate, except when a considerable fraction of the molybdate occupies less accessible interlayer positions. A maximum in the H2O2 decomposition rate as the H2O2 concentration is increased is due to the successive formation of mono-, di-, tri-, and tetraperoxomolybdates. This behavior was modeled successfully by using the equilibrium constants for formation of the Mo-peroxo complexes, and the rate constants for decay of the peroxomolybdates with 1O2 liberation. Time-resolved diffuse reflectance and Raman observations of the various MoO4(2-)-peroxide adducts are in line with the proposed kinetic scheme. Of all the Mo-peroxo species on the LDH, the triperoxomolybdate has the highest rate for decay to 1O2. Comparison with the kinetics of dissolved molybdate shows that the monomolecular decay of all peroxomolybdate species proceeds much faster at the LDH surface than in solution. Consequently, maximal rates per Mo atom are at least twice as high for the heterogeneous LDH catalyst as for the homogeneous systems.

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Studies on transition metal peroxo complexes. Part 8. The nature of peroxomolybdates and peroxotungstates in aqueous solution

Cited by 147 publications

References 3 publications

Mononuclear and dinuclear peroxotungsten complexes with co-ordinated dipeptides as potent inhibitors of alkaline phosphatase activity

Mononuclear and dinuclear peroxotungsten complexes with co-ordinated dipeptides as potent inhibitors of alkaline phosphatase activity

Highly Selective, Recyclable Epoxidation of Allylic Alcohols with Hydrogen Peroxide in Water Catalyzed by Dinuclear Peroxotungstate

Kinetic and Spectroscopic Study of¹O₂Generation from H₂O₂Catalyzed by LDH–MoO₄²⁻(LDH=Layered Double Hydroxide)

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Studies on transition metal peroxo complexes. Part 8. The nature of peroxomolybdates and peroxotungstates in aqueous solution

Cited by 147 publications

References 3 publications

Mononuclear and dinuclear peroxotungsten complexes with co-ordinated dipeptides as potent inhibitors of alkaline phosphatase activity

Mononuclear and dinuclear peroxotungsten complexes with co-ordinated dipeptides as potent inhibitors of alkaline phosphatase activity

Highly Selective, Recyclable Epoxidation of Allylic Alcohols with Hydrogen Peroxide in Water Catalyzed by Dinuclear Peroxotungstate

Kinetic and Spectroscopic Study of1O2Generation from H2O2Catalyzed by LDH–MoO42−(LDH=Layered Double Hydroxide)

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Kinetic and Spectroscopic Study of¹O₂Generation from H₂O₂Catalyzed by LDH–MoO₄²⁻(LDH=Layered Double Hydroxide)