Synthesis, characterization and catalytic activity of dioxidomolybdenum(VI) complexes of tribasic pentadentate ligands

Maurya, Mannar R.; Dhaka, Sarita; Avecilla, Fernando

doi:10.1016/j.poly.2013.08.050

Cited by 63 publications

(44 citation statements)

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“…We have recently explored the catalytic role of cis ‐[Mo VI O 2 ] 2+ complexes with ONO/ONS donor ligands in the oxidation and oxidative bromination of various organic substrates mediated by H 2 O 2 /NaHCO 3 . Most of these reactions are thought to proceed via an oxidoperoxido intermediate, the formation of which has been substantiated by UV/Vis spectroscopic evidence as well as single‐crystal X‐ray structures in some cases . In the present study, we have performed a detailed kinetic study and deduced the rate equation for oxygen atom transfer between DMSO and benzoin catalyzed by cis ‐[MoO 2 ] 2+ complexes of tripodal tetradentate ligands through high‐performance liquid chromatography.…”

Section: Introductionmentioning

confidence: 72%

Dioxidomolybdenum(VI) Complexes of Tripodal Tetradentate Ligands for Catalytic Oxygen Atom Transfer between Benzoin and Dimethyl Sulfoxide and for Oxidation of Pyrogallol

2016

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The reactions of the tripodal tetradentate ONNO donor ligands 6,6′‐{[(2‐morpholinoethyl)azanediyl]bis(methylene)}bis(2,4‐di‐tert‐butylphenol) (H2L1), 6,6′‐{[(2‐morpholinoethyl)azanediyl]bis(methylene)}bis(2,4‐dimethylphenol) (H2L2) and 6,6′‐{[(2‐morpholinoethyl)azanediyl]bis(methylene)}bis[2‐(tert‐butyl)‐4‐methylphenol] (H2L3) with [MoVIO2(acac)2] (acac = acetylacetonato) in a 1:1 molar ratio in MeOH gave the corresponding cis‐dioxidomolybdenum(VI) complexes [MoO2(L1)], [MoO2(L2)] and [MoO2(L3)], respectively, in excellent yields. These complexes were characterized by various spectroscopic (IR, UV/Vis, 1H and 13C NMR), electrochemical, thermogravimetric, single‐crystal XRD, and powder XRD (PXRD) studies. In these complexes, the geometry around the cis‐[MoO2]2+ core is distorted octahedral, and the ligands are tetradentate and coordinate through two Ophenolate, one Ntripodal, and one Nmorpholine atoms. One of the oxido groups and the morpholine nitrogen atom occupy the axial sites. These complexes were used for catalytic oxygen atom transfer between benzoin and dimethyl sulfoxide (DMSO) in acetonitrile at 80 °C, and the formation of benzil was followed by HPLC. Detailed kinetic studies revealed a first‐order rate in benzoin and catalyst, and the rate constant for the second‐order oxygen atom transfer reaction was 0.0162 m–1 h–1. The formation of the dinuclear intermediates [LMoV–µ‐O‐MoVL] was established by MALDI‐TOF MS and UV/Vis spectroscopy. Its reversible nature was further supplemented by UV/Vis spectroscopy. These complexes also catalyze the oxidation of pyrogallol in a fashion similar to that of transhydroxylases. Under aerobic conditions, the initially formed oxidation product phloroglucinol undergoes further oxidative coupling in the presence of H2O2 to give purpurogallin as the final product. This process follows Michaelis–Menten‐type kinetics with respect to pyrogallol; the kcat values obtained were 394, 300 and 247 h–1 for [MoVIO2(L1)], [MoVIO2(L2)] and [MoVIO2(L3)], respectively.

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Section: Introductionmentioning

confidence: 72%

Dioxidomolybdenum(VI) Complexes of Tripodal Tetradentate Ligands for Catalytic Oxygen Atom Transfer between Benzoin and Dimethyl Sulfoxide and for Oxidation of Pyrogallol

2016

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“…8,9 All new molybdenum complexes reported here have ability to catalyze secondary alcohols viz. Oxidation of alcohols catalyzed by molybdenum(VI) complexes has been studied using TBHP as well as H 2 O 2 as an oxidant.…”

Section: Catalytic Activity Studiesmentioning

confidence: 99%

“…[1][2][3] Recently, considerable efforts have been made towards investigating highly efficient catalytic processes for oxidation of alcohols. 8,9 A number of soluble molybdenum complexes bearing different ligands have been synthesized and employed as homogeneous catalysts for the epoxidation of alkenes; 10,11 molybdenum complexes catalyzing the oxidation of alcohols are also reported in the literature. To minimize harmful wastes, the development of catalytic oxidation procedures that involve green oxidants, e.g.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of secondary alcohols by conventional and microwave-assisted methods using molybdenum complexes of ONO donor ligands

2015

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New dioxidomolybdenum(VI) complexes, [Mo VI O 2 {Hdfmp(bhz) 2 }(MeOH)] 1, [Mo VI O 2 {Hdfmp(inh) 2 }(MeOH)] 2 and [Mo VI O 2 {Hdfmp(nah) 2 }(MeOH)] 3 of ligand H 3 dfmp(L) 2 I, are obtained by the condensation of 2,6diformyl-4-methylphenol (dfmp) and hydrazides (L) [L = benzoylhydrazide (bhz), isonicotinoylhydrazide (inh), and nicotinoylhydrazide (nah)], respectively. All these complexes are characterized in the solid state and in solution namely by elemental analyses, spectroscopic techniques (IR, electronic, 1 H and 13 C NMR) and thermogravimetric analyses. Single crystal X-ray analysis of complexes 1 and 3 confirms the coordination of the ligand in the dianionic (ONO 2À ) enolate-tautomeric form and one of the hydrazido moieties remains non-coordinated. Oxidation of secondary alcohols: 1-phenyl ethanol, 2-propanol and 2-butanol, catalyzed by these molybdenum complexes, using conventional liquid phase and microwaveassisted methods in the presence of 30% H 2 O 2 as an oxidant has been tested. The effects of various factors, such as temperature and amounts of catalyst, H 2 O 2 and solvent have been investigated. These alcohols under the optimized reaction conditions gave high yields of the respective ketone. Addition of an N-based additive reduces the reaction time considerably. Amongst the two methods studied, the microwave technique proves to be a time efficient system.

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“…A variety of physicochemical investigation of these compounds provides a clear explanation for their stereochemical and electronic properties. In spite of the important role of molybdenum in biological processes, its high potential as catalyst has made it even more attractive [7].…”

Section: Introductionmentioning

confidence: 99%

cis-Dioxido-molybdenum(VI) complexes of tridentate ONO hydrazone Schiff base: Synthesis, characterization, X-ray crystal structure, DFT calculation and catalytic activity

Ebrahimipour

Khabazadeh

Castro

et al. 2015

Inorganica Chimica Acta

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C NMR and electronic spectra. The structure of complexes has been accomplished by single crystal X-ray diffraction. All experimental results confirmed that both complexes have an octahedral geometry around the Mo(VI) central atom, which is coordinated by the donor atoms of the dianionic hydrazone ligand, two oxido groups and oxygen/nitrogen atoms of solvent molecules. Computational studies were also performed using DFT calculations at B3LYP/DGDZVP level of theory. Furthermore, their catalytic activities were investigated on the electrophilic reaction of indole with aldehydes in molten tetrabutyl ammonium bromide (TBAB) to obtain bis(indolyl)methane derivatives.

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Synthesis, characterization and catalytic activity of dioxidomolybdenum(VI) complexes of tribasic pentadentate ligands

Cited by 63 publications

References 63 publications

Dioxidomolybdenum(VI) Complexes of Tripodal Tetradentate Ligands for Catalytic Oxygen Atom Transfer between Benzoin and Dimethyl Sulfoxide and for Oxidation of Pyrogallol

Dioxidomolybdenum(VI) Complexes of Tripodal Tetradentate Ligands for Catalytic Oxygen Atom Transfer between Benzoin and Dimethyl Sulfoxide and for Oxidation of Pyrogallol

Oxidation of secondary alcohols by conventional and microwave-assisted methods using molybdenum complexes of ONO donor ligands

cis-Dioxido-molybdenum(VI) complexes of tridentate ONO hydrazone Schiff base: Synthesis, characterization, X-ray crystal structure, DFT calculation and catalytic activity

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