Molybdenum(VI)-dioxo complexes with linear and tripodal tetradentate ligands: models for the molybdenum(VI/V) centers of the molybdenum hydroxylases and related enzymes. 1. Syntheses and structures

Hinshaw, Carol J.; Peng, Gang; Singh, Raghuvir; Spence, J. T.; Enemark, John H.; Bruck, Michael A.; Kristofzski, J.G.; Merbs, Shannath L.; Ortega, Richard; Wexler, Pamela A.

doi:10.1021/ic00324a012

Cited by 103 publications

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“…[14] Bio-inspired dioxomolybdenum(VI) complexes have been prepared in great variety in recent years. [15] Close structural models represent dithiolene-based ligands, [16][17][18][19][20][21] but several oxomolybdenum complexes of non-dithiolene ligands, including pyridine dithiolates, [22,23] tris(pyrazolyl)borate lig-A C H T U N G T R E N N U N G ands, [24] 3,5-tert-butyl-pyrazolate ligands, [25,26] b-ketiminates, [27,28] and bis(phenolate) ligands, [29][30][31][32] were also investigated. Furthermore, biomimetic models have been developed in order to investigate the influence of the spectator oxo effect on the OAT reaction.…”

Section: Introductionmentioning

confidence: 99%

“…[37,38] In contrast, ligand H 2 (L7) with a 1,2-ethylenediamine linker leads to a cis-a molybdenum dioxo complex. [29] Several molybdenum dioxo complexes with bis(phenolate) ligands of the salan type have been reported and found to be catalysts for various OAT reactions. [29][30][31][32]39] Recently, Britovsek, Gibson, and co-workers studied the electronic effects on oxygen atom transfer reactions between DMSO and PPh 3 at 130 8C using cis-dioxomolybdenum(VI) complexes of ethylenediamine-based bis(phenolate) ligands.…”

Section: Introductionmentioning

confidence: 99%

“…[29] Several molybdenum dioxo complexes with bis(phenolate) ligands of the salan type have been reported and found to be catalysts for various OAT reactions. [29][30][31][32]39] Recently, Britovsek, Gibson, and co-workers studied the electronic effects on oxygen atom transfer reactions between DMSO and PPh 3 at 130 8C using cis-dioxomolybdenum(VI) complexes of ethylenediamine-based bis(phenolate) ligands. [39] All reported systems were found to exhibit a symmetric coordination sphere about the metal center with two identical oxo groups (cis-a).…”

Section: Introductionmentioning

confidence: 99%

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Mechanistic Insight into the Reactivity of Oxotransferases by Novel Asymmetric Dioxomolybdenum(VI) Model Complexes

Mayilmurugan

Harum

Volpe

et al. 2010

Chemistry A European J

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The asymmetric molybdenum(VI) dioxo complexes of the bis(phenolate) ligands 1,4-bis(2-hydroxybenzyl)-1,4-diazepane, 1,4-bis(2-hydroxy-4-methylbenzyl)-1,4-diazepane, 1,4-bis(2-hydroxy-3,5-dimethylbenzyl)-1,4-diazepane, 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)-1,4-diazepane, 1,4-bis(2-hydroxy-4-flurobenzyl)-1,4-diazepane, and 1,4-bis(2-hydroxy-4-chlorobenzyl)-1,4-diazepane (H(2)(L1)-H(2)(L6), respectively) have been isolated and studied as functional models for molybdenum oxotransferase enzymes. These complexes have been characterized as asymmetric complexes of type [MoO(2)(L)] 1-6 by using NMR spectroscopy, mass spectrometry, elemental analysis, and electrochemical methods. The molecular structures of [MoO(2)(L)] 1-4 have been successfully determined by single-crystal X-ray diffraction analyses, which show them to exhibit a distorted octahedral coordination geometry around molybdenum(VI) in an asymmetrical cis-β configuration. The Mo-O(oxo) bond lengths differ only by ≈0.01 Å. Complexes 1, 2, 5, and 6 exhibit two successive Mo(VI)/Mo(V) (E(1/2), -1.141 to -1.848 V) and Mo(V)/Mo(IV) (E(1/2), -1.531 to -2.114 V) redox processes. However, only the Mo(VI)/Mo(V) redox couple was observed for 3 and 4, suggesting that the subsequent reduction of the molybdenum(V) species is difficult. Complexes 1, 2, 5, and 6 elicit efficient catalytic oxygen-atom transfer (OAT) from dimethylsulfoxide (DMSO) to PMe(3) at 65 °C at a significantly faster rate than the symmetric molybdenum(VI) complexes of the analogous linear bis(phenolate) ligands known so far to exhibit OAT reactions at a higher temperature (130 °C). However, complexes 3 and 4 fail to perform the OAT reaction from DMSO to PMe(3) at 65 °C. DFT/B3LYP calculations on the OAT mechanism reveal a strong trans effect.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanistic Insight into the Reactivity of Oxotransferases by Novel Asymmetric Dioxomolybdenum(VI) Model Complexes

Mayilmurugan

Harum

Volpe

et al. 2010

Chemistry A European J

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“…For example, W can replace Mo in sulphite oxidase or nitrate reductase at the same coordination site but with remarkable differences in their behaviour, as these enzymes are less active or completely inactive upon the substitution of Mo by W [16][17][18]. Dioxomolybdenum(VI) complexes with amine bisphenol ligands have generally been prepared from stable and easily available MoO2(acac)2 or MoO2Cl2 and relevant ligand precursors in high yields using simple ligand displacement reactions [19][20][21][22][23][24][25][26], whereas occasional examples employ the use of an acidic solution of (NH4)6Mo7O24•4H2O [27][28][29]. Corresponding W compounds are made under dry conditions using [WO2Cl2(dme)] and ligands as free bases or sodium salts [30,31] or mixing free ligands and [W(eg)3] (eg = ethylene glycol) in alcohol solutions in the presence of ambient moisture [19,32].…”

Section: Introductionmentioning

confidence: 99%

Dioxomolybdenum(VI) and -Tungsten(VI) Amino Bisphenolates as Epoxidation Catalysts

Peuronen

Lehtonen

2016

Top Catal

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Low-cost metallate salts Na2MO4·2H2O (M = molybdenum, tungsten) react with a tridentate amine bisphenol bis(2-hydroxy-3-tert-butyl-5-methylbenzyl)methylamine (H2ONO tBu ) under ambient conditions in acidic methanol solutions. The reactions lead to the formation of isostructural dioxo complexes [MO2(ONO tBu )(MeOH)]·MeOH in convenient yields. Spectral data as well as X-ray analyses reveal these complexes to be isostructural. Both compounds were tested as catalysts for epoxidation of olefins using ciscyclooctene, cyclohexene, norbornene and styrene as substrates and tert-butyl hydroperoxide and hydrogen peroxide as oxidants. The molybdenum complex catalyses selectively the oxidation of cis-cyclooctene and norbornene to corresponding epoxides, whereas oxidation of cyclohexene and styrene lead low yields as the epoxidations were associated with the formation of other oxidation products. Corresponding tungsten complex shows lower activity for epoxidation of norbornene and practically no activity for other olefins. Both complexes can also catalyse the conversion of benzoin to benzil using dimethyl sulphoxide as an oxidant, while the molybdenum complex shows higher activity.

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“…6 A number of discrete dioxo-Mo VI complexes react with oxygen atom abstractors like phosphines, and a common occurrence in the process is the formation of dimeric complexes (equation 1, where Tp* = hydrotris(3,5-dimethyl-pyrazol-1-yl)borate). 7,8,9,10,11,12,13,14,15 Unless the dinuclear compounds are in rapid equilibrium with the mononuclear compounds, formation of dinuclear compounds terminates the catalytic process. Two general approaches have been used to prevent the dinucleation.…”

Section: Introductionmentioning

confidence: 99%

Design, synthesis, and characterization of a sterically encumbered dioxo molybdenum (VI) core

Sengar¹,

Basu²

2007

Inorganica Chimica Acta

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Dioxo-Mo VI complexes of general formula Tp*MoO 2 (p-SC 6 H 4 Dn) (6a-6c) (where Tp* = hydrotris (3,5-dimethyl-pyrazol-1-yl)borate and Dn= dendritic unit) have been synthesized and characterized by spectroscopy and mass spectrometry. 1 H NMR spectra of the metal complexes indicate that the C s local symmetry about the metal core does not change by the incorporation of dendritic functionality at the thiophenolato ring. Electrochemical data show ∼20 mV change in the redox potential in the complexes with dendritic ligands suggesting a very small perturbation in the redox orbital, which is also supported by small changes in the electronic spectra. The peak-to peak separation (ΔE p ) increases from 125 mV in 6(a) to 240 mV in 6(c), suggesting sluggish electron transfer in molecules with larger dendritic ligands.

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Molybdenum(VI)-dioxo complexes with linear and tripodal tetradentate ligands: models for the molybdenum(VI/V) centers of the molybdenum hydroxylases and related enzymes. 1. Syntheses and structures

Cited by 103 publications

References 1 publication

Mechanistic Insight into the Reactivity of Oxotransferases by Novel Asymmetric Dioxomolybdenum(VI) Model Complexes

Mechanistic Insight into the Reactivity of Oxotransferases by Novel Asymmetric Dioxomolybdenum(VI) Model Complexes

Dioxomolybdenum(VI) and -Tungsten(VI) Amino Bisphenolates as Epoxidation Catalysts

Design, synthesis, and characterization of a sterically encumbered dioxo molybdenum (VI) core

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