Rhodium(III) iodide is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula RhI₃. It is a black solid.

Preparation

Rhodium(III) iodide can be synthesised by the reaction of aqueous

potassium iodide Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are u ...

with rhodium(III) bromide. :RhBr₃ + 3KI → RhI₃ + 3KBr

Structure

RhI₃ adopts same

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

motif as AlCl₃ and YCl₃. The structure consists of

cubic Cubic may refer to: Science and mathematics * Cube (algebra), "cubic" measurement * Cube, a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex ** Cubic crystal system, a crystal system w ...

close-packed In geometry, close-packing of equal spheres is a dense arrangement of congruent spheres in an infinite, regular arrangement (or lattice). Carl Friedrich Gauss proved that the highest average density – that is, the greatest fraction of space occ ...

iodide ions and rhodium ions filling a third of the

octahedral In geometry, an octahedron (: octahedra or octahedrons) is any polyhedron with eight faces. One special case is the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex. Many types of i ...

interstices, forming a layers.

Reactivity

Rhodium(III) iodide is only known in the

anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...

form. Unlike the other rhodium(III) halides, it does not form

hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

s. The related anion hI₆sup>3− was previously thought not to form but has since been prepared by diffusion of RhCl₃·3H₂O through a layer of

hydroiodic acid Hydroiodic acid (or hydriodic acid) is a colorless liquid. It is an aqueous solution of hydrogen iodide with the chemical formula . It is a strong acid, in which hydrogen iodide is ionized completely in an aqueous solution. Concentrated aqueous ...

into

piperazine Piperazine () is an organic compound with the formula . In term of its structure, it can be described as cyclohexane with the 1- and 4-CH2 groups replaced by NH. Piperazine exists as deliquescent solid with a saline taste. Piperazine is freely sol ...

References

{{iodides Rhodium(III) compounds Iodides Platinum group halides