Dioxomolybdenum(VI) Complexes of Tripodal Nitrogen-Donor Ligands: Syntheses and Spectroscopic, Structural, and Electrochemical Studies, Including the Generation of EPR-Active Molybdenum(V) Species in Solution

Xiao, Zhiguang; Bruck, Michael A.; Doyle, Colleen; Enemark, John H.; Grittini, Carina; Gable, Robert W.; Wedd, Anthony G.; Young, Charles G.

doi:10.1021/ic00128a005

Cited by 80 publications

(212 citation statements)

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“…1 H, 13 C and 15 N NMR spectra clearly reveal two sets of chelate ligand atoms due to the reduction of symmetry from C 2 (1) to C 1 (5a-5c). Exemplarily, characteristic 1 H and 15 N resonances of 5a-5c are considered: the resonance of the imine protons H 7 (δ = 7.93 ppm, 1) splits into two resonances (H 7 , H 7Ј ) at δ = 7.98, 7.50 ppm (5a), [16] [9] Coordination of the phosphane ligand to the molybdenum atom in 5a-5c is directly seen by the characteristic 31 P NMR chemical shifts at δ = 2.4 ppm (5a), [16] 13.7 ppm (5b) and 29.9 ppm (5c), respectively, and the cross peaks to the protons H 7 , H 7Ј and H…”

Section: Resultsmentioning

confidence: 99%

Oxidomolybdenum(IV), ‐(V), ‐(VI) Complexes with Relevance to Molybdenum Enzymes: Oxygen Atom Transfer, Redox Chemistry and EPR Spectroscopy

Heinze

Fischer

2010

Eur J Inorg Chem

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The cis‐dioxidomolybdenum(VI) complex Mo(NN′)2O2 (1) [(NN′) = N‐(4‐hydroxyphenyl)‐2‐pyrrolatocarbaldimine] transfers one oxygen atom to phosphanes PMenPh3–n (n = 0–3) to give quantitatively the respective phosphane oxides OPMenPh3–n (OAT, oxygen atom transfer). The kinetics of these OAT reactions has been investigated spectrophotometrically. When offering excess PMenPh3–n (n = 1–3), oxido(phoshane)molybdenum(IV) complexes Mo(NN′)2O(PMenPh3–n) 5a–5c are isolated and characterized by multinuclear NMR spectroscopy (1H, 13C, 31P, 15N), IR spectroscopy, UV/Vis spectroscopy and mass spectrometry. The redox chemistry of the molybdenum(IV) complexes 5a–5c and of molybdenum(VI) complex 1 has been probed by preparative one‐electron oxidation and reduction, respectively, in combination with EPR spectroscopy under strictly anhydrous conditions. The reactivity of the resulting MoV species (ligand substitution, protonation, silyation) has been investigated to shed further light onto the biomimetic catalytic cycle of OAT from water to substrates in combination with two coupled electron proton transfer reactions (CEPT).

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Section: Resultsmentioning

confidence: 99%

Oxidomolybdenum(IV), ‐(V), ‐(VI) Complexes with Relevance to Molybdenum Enzymes: Oxygen Atom Transfer, Redox Chemistry and EPR Spectroscopy

Heinze

Fischer

2010

Eur J Inorg Chem

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“…The MOS calculated for the experimental structure 1 is 1.55 (14). Corresponding values for the DFT optimized structures 1'-S and 1'-DR are 1.58(17) and 1.47(15), respectively.…”

Section: Theoretical Studiesmentioning

confidence: 88%

Heptacoordinated Molybdenum(VI) Complexes of Phenylenediamine Bis(phenolate): A Stable Molybdenum Amidophenoxide Radical

et al. 2013

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The syntheses, crystallographic structures, magnetic properties, and theoretical studies of two heptacoordinated molybdenum complexes with N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (H 4 N 2 O 2 ) are reported. A formally molybdenum(VI) complex [Mo(N 2 O 2 )Cl 2 (dmf)] (1) was synthesized by the reaction between [MoO 2 Cl 2 (dmf) 2 ] and H 4 N 2 O 2 , whereas the other molybdenum(VI) complex [Mo(N 2 O 2 )(HN 2 O 2 )] (2) was formed when [MoO 2 (acac) 2 ] was used as a molybdenum source. Both complexes represent a rare case of the Mo VI ion without any multiply bonded terminal ligands. In addition, molecular structures, magnetic measurements, ESR spectroscopy, and density functional theory calculations indicate that complex 2 is the first stable molybdenum(VI) amidophenoxide radical.

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“…Complexes 1, 2, 5, and 6 exhibit two successive cath-A C H T U N G T R E N N U N G odA C H T U N G T R E N N U N G ic waves as well as their corresponding anodic waves (Table 4 and Supporting Information, Figure S1), which are assigned to the Mo VI !Mo V and Mo V !Mo IV redox processes, respectively. [29,31,[47][48][49] However, complexes 3 and 4 show only one cathodic and one anodic wave (Table 4) ) plot into the Randles-Sevcik equation [50] are of the same order as those observed for metal complexes undergoing two consecutive one-electron reduction processes. [31,37,39,41] The E 1/2 values of the Mo VI /Mo V redox potentials of the complexes from CV vary in the order 6 > 5 > 1 > 2 > 3 > 4 (Table 4), suggesting a decrease in Lewis acidity (ten- (Figure 2).…”

Section: Molecular Structures Of 1-4mentioning

confidence: 96%

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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Dioxomolybdenum(VI) Complexes of Tripodal Nitrogen-Donor Ligands: Syntheses and Spectroscopic, Structural, and Electrochemical Studies, Including the Generation of EPR-Active Molybdenum(V) Species in Solution

Cited by 80 publications

References 0 publications

Oxidomolybdenum(IV), ‐(V), ‐(VI) Complexes with Relevance to Molybdenum Enzymes: Oxygen Atom Transfer, Redox Chemistry and EPR Spectroscopy

Oxidomolybdenum(IV), ‐(V), ‐(VI) Complexes with Relevance to Molybdenum Enzymes: Oxygen Atom Transfer, Redox Chemistry and EPR Spectroscopy

Heptacoordinated Molybdenum(VI) Complexes of Phenylenediamine Bis(phenolate): A Stable Molybdenum Amidophenoxide Radical

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

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