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Issue 10, 2018
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Combined HPLC-ICP-AES technique as an informative tool for the study of heteropolyniobates

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Abstract

The combined HPLC-ICP-AES technique was applied to study formation of tungstoniobates and phosphomolybdoniobates. Reaction of potassium hexaniobate with tungstic acid results in the formation of mixed Nb/W Lindqvist hexametalates. The metal ratio depends on the relative amount of H2WO4 and reaction time. The most favored species are [Nb4W2O19]6− and [Nb3W3O19]5− which equilibrate with hexaniobate. Formation of [Nb2W4O19]4− was also observed; its share gradually increases with increasing amount of tungstic acid and decreasing pH. Reaction of tungstic acid with telluropentaniobate [TeNb5O19]7− results only in substitution of W for Te producing the same mixed Nb/W Lindqvist anions, but with different distribution of the individual species. The reaction of phosphomolybdic acid (H3PMo12O40) with a niobium oxalate complex, [NbO(C2O4)2(H2O)2], leads to the formation of mixed P/Nb/Mo Keggin anions, unambiguously detected for the first time. Only [PMo11NbO40]4− and [PMo10Nb2O40]5− were observed over the whole concentration range. No trisubstituted [PMo9Nb3O40]6− was detected in the substitution reaction, but is accessible from the self-assembly reaction of the niobium oxalate complex, phosphoric acid, and molybdate.

Graphical abstract: Combined HPLC-ICP-AES technique as an informative tool for the study of heteropolyniobates

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Supplementary files

Article information


Submitted
11 Oct 2017
Accepted
19 Mar 2018
First published
20 Mar 2018

New J. Chem., 2018,42, 7949-7955
Article type
Paper

Combined HPLC-ICP-AES technique as an informative tool for the study of heteropolyniobates

P. A. Abramov, T. E. Romanova, V. V. Volchek, A. A. Mukhacheva, N. B. Kompankov and M. N. Sokolov, New J. Chem., 2018, 42, 7949
DOI: 10.1039/C7NJ03917D

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