Osmium iodide refers to compounds of osmium with the formula OsIn. Several have been mentioned in the literature, but only the triiodide has been verified by X-ray crystallography.[1][2]
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]
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 osmic acid (OsO2•2H2O) and hydroiodic acid.[4] However on attempted reproduction, this substance was found to be dihydroxonium hexaiodoosmate ((H3O+)2OsI62–). When heated this did not form a tetraiodo compound, and instead formed mono, di, and tri-iodo osmium compounds.[2]