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BY-NC-ND 3.0 license Open Access Published by De Gruyter June 2, 2014

Kristallstrukturen und Schwingungsspektren zweier isomerer Oktadekawolframatodiarsenate, (NH4)6As2W18O62 ·nH2O/ Crystal Structures and Vibrational Spectra of Two Isomers of Octadecatungsto-diarsenate (NH4)6As2W18O62 · nH2O

Holger Neubert and Joachim Fuchs

Abstract

Six possible structures of As2W18O626- are discussed, and an exact nomenclature is proposed. The structures of the isomeric title compounds (I and II) were determined by X-ray diffraction. I crystallizes in space group P I with lattice parameters a = 12.965(4), b = 14.803(5), c = 18.515(6) Å; a = 96.280(23)°, β = 91.420(25)°, γ = 115.320(25)°. The anion has the configuration first observed in K6P2W18O62 · 14H2O (Dawson-structure). II was not known until now. It crystallizes in the trigonal space group R3 with lattice parameters a - b - 37.857(32). c = 13.108( 13) Å; α = β = 90°, γ = 120°. The structure of this anion differs from the Dawson-structure by the 60° rotation of both polar groups of three WO6-octahedra (β-type), followed by the 60° rotation of one of the two new AsW9O31-units. Both rotations are about the 3-fold axis. The anion is centrosymm etric. Vibrational spectra and preparation of the isomers are described.

Received: 1987-3-4
Revised: 1987-5-11
Published Online: 2014-6-2
Published in Print: 1987-8-1

© 1946 – 2014: Verlag der Zeitschrift für Naturforschung

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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