Rhodium(III) iodide explained

Rhodium(III) iodide is an inorganic compound with the formula RhI₃. It is a black solid.

Preparation

Rhodium(III) iodide can be synthesised by the reaction of aqueous potassium iodide with rhodium(III) bromide.

RhBr₃ + 3KI → RhI₃ + 3KBr

Structure

RhI₃ 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.^[1]

Reactivity

Rhodium(III) iodide is only known in the anhydrous form. Unlike the other rhodium(III) halides, it does not form hydrates. The related anion [RhI₆]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.^[2]

Notes and References

1. Strukturuntersuchungen an Rhodiumhalogeniden . K. . Brodersen . G. . Thiele . I. . Recke . . 14 . 1 . 1968 . 151–152 . 10.1016/0022-5088(68)90214-2 .
2. Efficient Diffusion-Controlled Ligand Exchange Crystal Growth of Isostructural Inorganic–Organic Halogenidorhodates(III): The Missing Hexaiodidorhodate(III) Anion . Maciej . Bujak . . 2015 . 15 . 3 . 1295–1302 . 10.1021/cg501694d .