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Updated: Jun 2, 2026
09:56
High Resolution Physical Characterization of Single Metallic Nanoparticles
Published on: June 28, 2019
Borotungstate polyoxometalates: multinuclear NMR structural characterization and conversions in solutions
Raisa I Maksimovskaya1, Gennadii M Maksimov
1Boreskov Institute of Catalysis, Lavrentiev av. 5, Novosibirsk 630090, Russia. rimax@catalysis.ru
Inorganic Chemistry
|April 30, 2011
Summary
This study identifies novel heteropolyanions, protonated lacunary heteropolyanion [HBW(11)O(39)](8-) (BW(11)) and [H(3)BW(13)O(46)](8-) (BW(13)), in aqueous solutions using NMR. It details their structures and pH-dependent transformations, revealing insights into polyoxotungstate chemistry.
Area of Science:
- Inorganic Chemistry
- Solution Chemistry
- Spectroscopy
Background:
- Heteropolyanions are complex inorganic species with diverse applications.
- The existence and structure of specific protonated heteropolyanions like BW(11) and BW(13) were previously inferred but not directly confirmed.
- Understanding the speciation and transformations of these polyoxotungstates in aqueous solution is crucial for their controlled synthesis and application.
Purpose of the Study:
- To definitively identify and characterize the heteropolyanions [H(3)BW(13)O(46)](8-) (BW(13)) and protonated lacunary heteropolyanion [HBW(11)O(39)](8-) (BW(11)) in aqueous solutions.
- To elucidate the structural details, including isomeric form and protonation sites, of BW(11) and BW(13) using advanced NMR techniques.
- To investigate and map the pH-dependent interconversion pathways between BW(11), BW(13), and other related polyoxotungstates (BW(12), B(3)W(39)) in solution.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy, specifically (183)W and (17)O NMR, was employed to identify and characterize the heteropolyanions.
- Analysis of (183)W NMR spectra included examining coupling satellites ((2)J(W-O-W)) to determine tungsten-tungsten connectivities and isomeric forms.
- (17)O NMR spectra were utilized to confirm the protonation state and delocalization of protons within the polyanions.
Main Results:
- The heteropolyanions BW(13) and BW(11) were unambiguously identified in aqueous solutions within the pH range of 5-7.5.
- NMR data confirmed BW(11) as the α isomer and elucidated the specific proton delocalization sites on BW(11) and BW(13).
- The study mapped the pH-dependent conversions: BW(11) transforms to BW(13) (pH 7.5-6), which further converts to BW(12) and B(3)W(39), with BW(12) being stable across a broad pH range (0-7.5).
Conclusions:
- This work provides direct spectroscopic evidence for the existence and structures of BW(13) and BW(11) in solution.
- The detailed understanding of their protonation and interconversion mechanisms offers critical insights into polyoxotungstate solution chemistry.
- The findings are essential for the rational design and application of these unique inorganic compounds.
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