Tungsten Oxytetrachloride and Several Tungstate Salts

Tungsten oxytetrachloride is a good starting material to prepare other oxotungsten (VI) complexes and to incorporate tungsten species into silica-based materials. The usual preparations of tungsten oxytetrachloride, which are based on tungstic acid, are somewhat tedious and require prolonged heating times. The preparation of WOCl4 from anhydrous sodium tungstate, reported in this chapter, is an improved and simplified method. The preparation of (n-Bu4N)2W6O19 reported here is a simplification of the procedure given in this series by Fournier and Fuchs. Phosphoric, phosphinic, and phosphonic acids form complexes with both peroxotungstates and peroxomolybdates. In particular, phenylphosphonic acid forms a complex that is a very convenient alkene epoxidation catalyst. The chapter discusses the procedures and properties of tungsten oxytetrachloride, tetrabutylammonium hexapolytungstate, di(cetylpyridinium) peroxoditungstate, and bis(tetrabutylammonium) phenylphosphonatodiperoxotungstate .