Yttrium Containing Dimeric and Tetrameric Keggin Type Phosphotungstates: Syntheses, Crystal Structure and Catalytic Activity for Alcohol Oxidation Using H2O2 as an Oxidant in Water

Author(s): Firasat Hussain , Mukesh K. Saini , Rakesh Gupta , Surendra Singh .

Journal Name: Current Catalysis

Volume 5 , Issue 1 , 2016

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Background: The aim of this paper is to introduce about the synthetic strategy of new polyoxometalate compounds using single step reaction procedure and their oxidative catalytic activity. In this context herein, we report green oxidation process for the oxidation of alcohols to carbonyl compounds, using yttrium containing dimeric K11[Y(PW11O39)2]·35H2O (1) and tetrameric K16Na6[(PY2W10O38)4 (W3O8)(OH)4(H2O)2]·56H2O (2) phosphotungstates compounds in the presence of H2O2 oxidant and reused up to five catalytic cycles.

Methods: The conventional aqueous solution method was used to synthesize a single crystalline solid material with good yields. The different parameters such as pH, temperature, time and nature of ligand were taken under consideration for the single step reaction procedure under mild conditions. The catalytic alcohol oxidation reactions were performed using very less catalyst loading and H2O2 co-oxidant in eco-friendly water as a solvent.

Results: The solid state characterization of compounds 1 and 2 was performed using single crystal X-ray diffraction, FT-IR spectroscopy, thermogravimetric analysis and solution stability was also checked by 31P NMR spectroscopy. The ICP-AES analysis was performed for the chemical composition of the compounds. A variety of primary and secondary alcohols were oxidized to corresponding carbonyl compounds with excellent yields in presence of very less catalyst loading and 2:1 H2O2/substrate ratio in water.

Conclusion: In conclusion, we have isolated two yttrium containing Keggin type dimeric and tetrameric phosphotungstate complexes by the single step reaction of K14[P2W19O69(H2O)]·24H2O POM ligand with Y(NO3)3·6H2O salt. The isolated compounds were further characterized with FT-IR spectroscopy, single crystal X-ray diffraction, 31P NMR, thermogravimetric and elemental analysis. The catalytic alcohol oxidation studies show good catalytic conversions, and finally FT-IR spectra of recovered catalysts after fifth cycle shows both catalysts retains their identity after fifth catalytic cycle.

Keywords: Polyoxometalates, yttrium, catalysis, alcohol oxidation.

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Article Details

Year: 2016
Page: [66 - 76]
Pages: 11
DOI: 10.2174/2211544705666160210231326

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