Aluminium iodide (AlI3)

Structure and properties

Aluminium in these compounds typically has a +3 formal oxidation state while iodine is −1. AlI3 exhibits significant covalent character and can associate into dinuclear units under some conditions; it is hygroscopic and sensitive to moisture, hydrolyzing to give hydrogen iodide and aluminium oxides or hydroxides. Physical appearance varies with purity and preparation method.

Preparation

Two straightforward laboratory routes are the direct reaction of aluminium metal with iodine or the action of hydrogen iodide on aluminium. The elemental synthesis combines clean aluminium powder and iodine under controlled heating. Variants produce adducts by dissolving AlI3 in donor solvents to isolate complexes.

Reactivity and uses

• Acts as a Lewis acid and can promote or catalyze transformations in organic chemistry.
• Serves as a source of iodide for halide exchange and to prepare organoiodine reagents.
• Forms stable adducts with ethers and other Lewis bases useful in synthesis and characterization.

Handling and notable facts

Aluminium iodide reacts with water to release corrosive hydrogen iodide gas, so it is stored under inert atmosphere and handled with appropriate protective equipment. For further general information on the category of this substance see chemical compound, and for elemental context consult entries on aluminium and iodine.