Study of the Heteropolyacid H21B3W39O 132 · nH2O
Russian Journal of Inorganic Chemistry
, E-ISSN: 1531-8613
Boreskov Institute of Catalysis SB RAS
The heteropolyacid H(21)B(3)W(39)O(132)center dot nH(2)O (B3W39) was studied by solid-state IR spectroscopy and differential thermal analysis and by W-183, O-17, and B-11 NMR in solution. The NMR spectra of the B3W39 anion, which consists, according to structural data, of three equivalent BW13 fragments, confirmed the integrity of the HPA in solutions but revealed the deviation from the C-s and C-3h symmetry determined previously, which results in structure chirality. Potentiometric titration showed the nonequivalence of the HPA protons, only 11 of which are strongly acidic. Concentrated (>= 0.05 M) solutions of HPA are unstable; after several days, H5BW12O40 and tungstic acid can be isolated from the solutions. On heating, solid B3W39 starts to decompose into the same products below 200 degrees C.