The reaction between ZnO and Molten K2S2O7 forming K2Zn(SO4)2, studied by Raman and IR Spectroscopy and X-ray Diffraction

The reaction between zinc oxide and molten potassium pyrosulfate at 500 °C was shown by Raman spectroscopy to be a 1:1 reaction. By lovering the temperature, colorless crystals could be formed. The crystal structure was determined: Space group = P21/c, Z = 4, a = 5.3582(11), b = 8.7653(18), c = 16.153(3) Å, b = 91.78(3)o, wR2 = 0.0758 for all 1930 ? independent reflections.

The compound, K2Zn(SO4)2, contained trigonally bipyramidal zinc coordinated to five oxygen atoms, with Zn-O bonds of normal length (~ 2.04 ± 0.05 Å), equitorial bonds being slightly shorter on the average. The O-Zn-O angles were approximately 90o and 120o. The oxygens were all bridging to the two sulfur atoms forming nearly perfect tetrahedral SO42- groups.

The K+ ions were placed in between these ZnO5 hexahedra, which formed a three-dimensional network. Bond distances and angles are compared with literature values. Empirical correlations between S-O bond distances and average O-S-O bond angles followed a previously found trend. IR and Raman spectra were obtained and tentatively assigned.