Selenium Oxyfluoride, SeOF₂

When dry hydrogen fluoride vapour is passed over selenium dioxide, the former is rapidly absorbed, the product liquefying and becoming warm. From this liquid Prideaux has isolated a product approximating to the composition SeO₂.5HF, but a definite oxyfluoride does not appear to be obtainable by this method. The Selenium Oxyfluoride, SeOF₂, may be prepared by passing selenium oxychloride vapour over silver fluoride at 140° to 200° C.; the reaction begins suddenly, and copious fumes are evolved which may be condensed to a colourless liquid of density 2.67 and boiling-point 124° C. This solidifies to an ice-like mass which melts at 4.6° C. Glass is readily attacked by the liquid or vapour, a white deposit of selenium dioxide being formed:

2SeOF₂ + SiO₂ = 2SeO₂ + SiF₄.

The reaction with red phosphorus is violent and accompanied by inflammation, the products being similar to those described with the tetrafluoride. The oxyfluoride is hydrolysed by water with evolution of heat.