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Title: Dioxidomolybdenum(VI) Complexes of Tripodal Tetradentate Ligands for Catalytic Oxygen Atom Transfer between Benzoin and Dimethyl Sulfoxide and for Oxidation of Pyrogallol
Authors: Maurya, Mannar Ram
Uprety B.
Avecilla F.
Published in: European Journal of Inorganic Chemistry
Abstract: 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 and13C 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 Nmorpholineatoms. 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–1h–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 H2O2to give purpurogallin as the final product. This process follows Michaelis–Menten-type kinetics with respect to pyrogallol; the kcatvalues obtained were 394, 300 and 247 h–1for [MoVIO2(L1)], [MoVIO2(L2)] and [MoVIO2(L3)], respectively. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Citation: European Journal of Inorganic Chemistry, 2016(29): 4802-4813
Issue Date: 2016
Publisher: Wiley-VCH Verlag
Keywords: Kinetics
Oxido ligands
Tripodal ligands
ISSN: 14341948
Author Scopus IDs: 7005255411
Author Affiliations: Maurya, M.R., Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, 247667, India
Uprety, B., Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, 247667, India
Avecilla, F., Departamento de Química Fundamental, Universidade da Coruña, Campus de A Zapateira, A Coruña, 15071, Spain
Funding Details: 
Corresponding Author: Maurya, M.R.; Department of Chemistry, India; email:
Appears in Collections:Journal Publications [CY]

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