The Reaction Between MoO3 and Molten K2S2O7 Forming K2MoO2(SO4)2, Studied by Raman and IR Spectroscopy and X-Ray Crystal Structure Determination

Abstract

The reaction between molybdenum trioxide and molten potassium pyrosulfate was shown by Raman spectroscopy at 430 °C to be a 1:1 reaction. By tempering of the compound, colorless crystals could be formed. The structure was determined; crystal data: Space group = P21/c, Z = 4, a = 9.0144(3), b = 12.4540(4), c = 8.8874(3) Å, β = 112.194(1)°, wR2 = 0.0897 for 3491 independent reflections. The compound, K2MoO2(SO4)2, contains MoO22+ core ions in distorted octahedral coordination, with two short (~1.69 Å) terminal bonds in cis-configuration (the O-Mo-O angle is 103.1(2)°), and with two long (~2.18 Å) bonds in trans-position to the short ones, and with two bonds of intermediate (~2.01 Å) length, all four bridging oxygens belonging to different sulfato groups. The K+ ions are placed in between strands of MoO6 octahedra, connected along the c-axis by two different kinds of bridging sulfato groups. Bond distances and angles are compared with literature values. Empirical correlations between bond distances and bond orders and bond order sums (approximating oxidation states) are given for all atoms. IR and Raman spectra were obtained and tentatively assigned.