Raman spectroscopy evidence of 1:1:1 complex formation during dissolution of WO3 in a melt of K2S2O7:K2SO4

Highly inert yellow solid WO3 was found to be soluble in considerable amounts in molten K2S2O7 at elevated temperatures (∼650 °C), if only similar molar amounts of sulfates were also present. The dissolution reaction of WO3 into a melt consisting of a 1:1 molar mixture of K2S2O7 and K2SO4 was studied in detail, and Raman spectroscopy was used to characterize the products. In combination with single crystal X-ray crystal structure determination, it was shown that a new dimeric compound, K8[{WVIO2(SO4)2}2(μ-SO4)2], was formed and its assigned Raman spectrum at room temperature is given. The WO22+ cores of the dimeric complex have their symmetrical and antisymmetrical stretching modes ν1(WO22+) and ν3(WO22+) at around 1054 (strong) and 1042 (weak), and the bending mode ν2(WO22+) at around 292 (medium intensity), respectively (positions given in cm−1).