Struktur und Schwingungsspektrum des α-Undekawolframatophosphats Na₂[N(CH₃)₄]₄HPW₁₁O₃₉ · 7H₂O / Structure and Vibrational Spectrum of the α-Undecatungstophosphate Na₂[N(CH₃)₄]₄HPW₁₁O₃₉ · 7H₂O

Abstract

<jats:p>The crystal structure of the compound Na<jats:sub>2</jats:sub>[N(CH<jats:sub>3</jats:sub>)<jats:sub>4</jats:sub>]<jats:sub>4</jats:sub>HPW<jats:sub>11</jats:sub>O<jats:sub>39</jats:sub> · 7H<jats:sub>2</jats:sub>O was solved by X-ray diffraction. It crystallizes in the space group C2/m with lattice parameters a= 23.895 Å, b = 11.417 Å, c = 28.930 Å, β= 126.0°.</jats:p><jats:p>The distances between the tungsten atoms and the kind of bridging by oxygen atoms prove the α-isomer. The differences between the vibration spectra of α-undecatungsto-phosphate and α-dodecatungstophosphate are discussed</jats:p>

Structural Studies of Keggin‐Type Polyoxotungstates by Extended X‐ray Absorption Fine Structure Spectroscopy

“…Finally, the W-O distance to the oxygen of the central PO 4 group was found to be 2.412 Å. These values are comparable to those reported for [PW 11 O 39 ] 7- [30] and [SiW 11 O 39 ] 8-, [31] obtained by X-ray crystallography. In these studies the position of the vacancy could not be located with certainty.…”

“…[25,30] For the different anions EXAFS data allowed the determination of bond lengths and other interatomic distances in the vicinity of target atoms. The influence of the lacuna or of substituting metals on the W-O bond lengths was not, in general, very large, but could be noticed.…”

“…In these studies the position of the vacancy could not be located with certainty. [30,31] Figure 3 shows the W L III edge EXAFS spectrum and the Fourier transform for the solid samples of TBA salts of PW 11 Mn and PW 11 Fe. The results from the curve fitting are presented in Table 4.…”

Compared Behaviours of Dawson-Type Tungstodiarsenates and -diphosphates

“…As a matter of fact, it was pointed out that the vacancy in such species is statistically distributed over several or all of the equivalent positions. [26,27] Therefore, although the same kind of derivation as above could have been carried out using the crystallographic determinations on As 2 W 18 by Neubert and Fuchs, [28] we found that the following complementary qualitative observations might prove more useful. From a general point of view in the Dawson-type tungstodiphosphates and tungstodiarsenates, the physical behaviour of a vacancy depends on its location in the polyoxometalate frame.…”

Keggin-type polyoxotungstates as mushroom tyrosinase inhibitors - A speciation study

“…S2 and Table S1) were Na 3 [PW 12 O 40 ] 21 (abbreviated: [PW 12 ] 3− ), K 4 [SiW 12 O 40 ] 29 ( [SiW 12 ] 4− ), K 5 [BW 12 O 40 ] 30 ( [BW 12 ] 5− ), Na 5 [AlW 12 O 40 ] 31 ( [AlW 12 ] 5− ), Na 6 [H 2 W 12 O 40 ] 32 ( [H 2 W 12 ] 6− ), Na 6 [BeW 12 O 40 ] 33 ( [BeW 12 ] 6− ), K 5 [PW 11 O 39 {Ni(H 2 O)}] 34 ( [PW 11 Ni] 5− ). The lacunary anions K 7 [PW 11 O 39 ] 35 , K 8 [SiW 11 O 39 ] 36 and Na 9 [AlW 11 O 39 ] 31 were prepared as control compounds to account for the potential hydrolysis of the corresponding Keggin POTs. Metatungstate [H 2 W 12 ] 6− is the most common Keggin cluster with net charge 6−.…”