Rhodium(III) iodide

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.

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.

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