Issue 19, 2001

Synthesis and characterization of tri-titanium(iv)-1,2,3-substituted α-Keggin polyoxotungstates with heteroatoms P and Si. Crystal structure of the dimeric, Ti–O–Ti bridged anhydride form K10H2[α,α-P2W18Ti6O77]·17H2O and confirmation of dimeric forms in aqueous solution by ultracentrifugation molecular weight measurements

Abstract

The preparation and characterization of the α-Keggin-type, novel tri-TiIV-1,2,3-substituted polyoxotungstates with heteroatoms P and Si are described. The molecular structure of K10H2[α,α-P2W18Ti6O77]·17H2O 1, obtained as a main product (30.4% yield) from the 1 ∶ 3 molar ratio reaction of tri-lacunary precursor Na9[A-PW9O34]·19H2O with Ti(SO4)2·4H2O in aqueous solution, was determined by X-ray structure analysis. It had the dimeric, anhydride structure formed by three Ti–O–Ti bonds linking two Keggin [α-1,2,3-PW9Ti3O40]9− units. From the filtrate after 1 was filtered off, a different compound 2 was obtained as a minor product. A related α-Keggin tri-TiIV-1,2,3-substituted polyoxotungstate with heteroatom Si, the dimeric anhydride form K10H4[α,α-Si2W18Ti6O77]·15H2O 3, was obtained as a main product (31.1% yield) from a 1 ∶ 3 molar ratio reaction of Na10[A-α-SiW9O34]·15H2O with Ti(SO4)2. Ultracentrifugation molecular weight measurements under less acidic conditions revealed that 1 and 3 were present as dimers in aqueous solution. Characterization of 1 and 3 was also accomplished by complete elemental analyses, TG/DTA, FTIR and solution (31P and 183W) NMR spectroscopies.

Graphical abstract: Synthesis and characterization of tri-titanium(iv)-1,2,3-substituted α-Keggin polyoxotungstates with heteroatoms P and Si. Crystal structure of the dimeric, Ti–O–Ti bridged anhydride form K10H2[α,α-P2W18Ti6O77]·17H2O and confirmation of dimeric forms in aqueous solution by ultracentrifugation molecular weight measurements

Supplementary files

Article information

Article type
Paper
Submitted
02 Apr 2001
Accepted
19 Jun 2001
First published
06 Sep 2001

J. Chem. Soc., Dalton Trans., 2001, 2872-2878

Synthesis and characterization of tri-titanium(IV)-1,2,3-substituted α-Keggin polyoxotungstates with heteroatoms P and Si. Crystal structure of the dimeric, Ti–O–Ti bridged anhydride form K10H2[α,α-P2W18Ti6O77]·17H2O and confirmation of dimeric forms in aqueous solution by ultracentrifugation molecular weight measurements

K. Nomiya, M. Takahashi, K. Ohsawa and J. A. Widegren, J. Chem. Soc., Dalton Trans., 2001, 2872 DOI: 10.1039/B102942H

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