Rhodium(III) iodide
# Rhodium(III) iodide

Rhodium(III) iodide is an inorganic compound with the formula $RhI_3.$ It is a black solid.

## Preparation

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

    $RhBr_3$ + 3KI → $RhI_3$ + 3KBr

## Structure

$RhI_3$ adopts same crystal structure motif as $AlCl_3$ and $YCl_3.$ 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 $[RhI_6]^{3−}$ was previously thought not to form but has since been prepared by diffusion of $RhCl_3·3H_2O$ through a layer of hydroiodic acid into piperazine.

