quality:correction, information:filtering, structural:scholar_edition
Halogen compounds

Selenium reacts with fluorine to form selenium hexafluoride:

In comparison with its sulfur counterpart (sulfur hexafluoride), selenium hexafluoride (SeF) is more reactive and is a toxic pulmonary irritant. Selenium tetrafluoride is a laboratory-scale fluorinating agent.

The only stable chlorides are selenium tetrachloride (SeCl) and selenium monochloride (Se Cl), which might be better known as selenium(I) chloride and is structurally analogous to disulfur dichloride. Metastable solutions of selenium dichloride can be prepared from sulfuryl chloride and selenium (reaction of the elements generates the tetrachloride instead), and constitute an important reagent in the preparation of selenium compounds (e.g. Se). The corresponding bromides are all known, and recapitulate the same stability and structure as the chlorides.

The iodides of selenium are not well known, and for a long time were believed not to exist. There is limited spectroscopic evidence that the lower iodides may form in bi-elemental solutions with nonpolar solvents, such as carbon disulfide and carbon tetrachloride; but even these appear to decompose under illumination.

Some selenium oxyhalides— seleninyl fluoride (SeOF) and selenium oxychloride (SeOCl)—have been used as specialty solvents.