Osmium iodides

Osmium(I) iodide is the iodide of osmium with the formula OsI. It is a metallic grey solid produced by the reaction of osmium tetroxide and hydroiodic acid heated in a water bath for 48 hours in a carbon dioxide atmosphere. This compound is amorphous.^[2]

Osmium(II) iodide is the iodide of osmium with the formula OsI₂. It is a black solid^[3] produced by the reaction of osmium tetroxide and hydroiodic acid at 250 °C in nitrogen:^[2]

${\displaystyle {\ce {OsO4 + HI -> OsI2 + H2O}}}$

This compound decomposes in contact with water.^[3]

Osmium(III) iodide is the iodide of osmium with the formula OsI₃. This black solid is produced by heating hexaiodoosmic acid(H₂OsI₆).^[2] This compound is insoluble in water.^[3]

What was claimed to be osmium(IV) iodide was produced by the reaction of osmium dioxide and hydroiodic acid.^[4] However on attempted reproduction, this substance was found to be hexaiodoosmic acid H₂OsI₆. When heated this did not form a tetraiodo compound, and instead formed mono, di, and tri-iodo osmium compounds. The ammonium salt, (NH₄)₂OsI₆, is known.^[2]

When potassium iodide is added to a solution containing osmium tetroxide and hydrochloric acid, a green solution of H[OsI₅(H₂O)] is obtained, which also contains potassium hexaiodoosmate K₂OsI₆ and a mixed halidoosmate of the type K₂OsCl_xI_x.^[5]