CRYSTAL STRUCTURE OF SODIUM-STRONTIUM PARATUNGSTATE B, Na6Sr2[W12O40(OH)2]в€™24H2O
S. V. Radio, N. I. Gumerova, V. N. Baumer
Keywords: paratungstate B anion, isopolytungstate, crystal structure, FTIR spectroscopy, single crystal X-ray analysis
Abstract
From the acidified solution of the Na2WO4–HNO3–Sr(NO3)2–H2O system, the white crystals of sodium-strontium paratungstate B Na6Sr2[W12O40(OH)2]∙24H2O (I) are isolated. By FTIR spectroscopy, the isopoly anion is shown to belong to the structural type of paratungstate B. Using single crystal X‑ray analysis the structure of I is solved: monoclinic, space group P21/n, a = 12.5435(3) Å, b = 12.1544(3) Å, c = 18.8080(4) Å, β = 93.440(2)°, V = 2862.28(12) Å3 at T = 293 K, Z = 2, ρcalc = 4.207 g/cm3. Found that [W12O40(OH)2]10– paratungstate B anions are cross-linked in a layer via the SrO9 and NaO6 polyhedra, and cross-linking in a three-dimensional structure occurs via the NaO6 and NaO7 polyhedra. By DTA, the thermal properties of the salt are studied. By FTIR spectroscopy, it is found that under annealing of I the [W12O40(OH)2]10– paratungstate B anion exists in the structure up to 200 °C.
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