Rhodium(III) iodideRhodium iodide is an inorganic compound with the formula RhI3. It is a black solid.PreparationRhodium iodide can be synthesised by the reaction of aqueous potassium iodide with rhodium(III) bromide.StructureRhI3 adopts same crystal structure motif as AlCl3 and YCl3. The structure consists of cubic close-packed iodide ions and rhodium ions filling a third of the octahedral interstices, forming a layers.ReactivityRhodium iodide is only known in the anhydrous form. Unlike the other rhodium halides, it does not form hydrates. The related anion 3− was previously thought not to form but has since been prepared by diffusion of RhCl3·3H2O through a layer of hydroiodic acid into piperazine.