Hydrogen Pentafluorooxoselenate VI

Hydrogen pentafluorooxoselenate (VI) is the main source of the extremely electronegative ligand [SeOFs]. This ligand and [TeOFs] are, for example, the only groups that form stable covalent derivatives of the types Xe(SeOFs)2, Xe(TeOFs)4, U(TeOFs)6, and others. In contrast, the chemistry of the SOFs 

During the synthesis of HSeOF, contact with glass or oxidizable materials must be avoided. The best materials for these substances are Kel-F [poly(tri-fluorochloroethylene)], FEP [poly(perfluoroethylenepropylene)], and stainless steel. To prepare HSeOFs completely free from HF, an all-Kel-F distillation column is necessary. 

The procedure is based on a typical equilibrium reaction, and the equilibrium is slowly shifted by separating the volatiles HF, Se02F2, and HSeOFs from the nonvolatile H2Se04, 

KSeOFs, Xe(SeOFs)2) and Br(SeOFs)3. The yield is never better than 70 g 

For a complete separation of the H2Se04 free mixture, fractional distillation through a 75-cm long, all-Kel-F column is necessary. This must be manufactured in a machine shop from Kel-F tubes and pieces, as it is not commercially available. A drawing of such a distillation column is given in Fig. 1. The coils of the distillation head must be cooled with a -40° methanol or acetone solution. 

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