Nickel(II) iodide

Nickel(II) iodide is an inorganic compound with the chemical formula NiI₂. It is a black solid that is used in various chemical reactions, particularly in organic synthesis and materials science. Nickel(II) iodide is one of the several nickel halides, being composed of nickel in the +2 oxidation state and iodine.

Properties

Nickel(II) iodide is a black, crystalline solid at room temperature. It is soluble in water, forming a yellow solution, and it can also dissolve in other polar solvents. The compound has a high melting point, indicative of its ionic nature. In terms of its structure, NiI₂ adopts a similar lattice structure to other nickel halides, where nickel is coordinated by six iodide ions in an octahedral geometry.

Synthesis

Nickel(II) iodide can be synthesized by the direct reaction of nickel metal with iodine. The reaction is typically carried out at elevated temperatures:

\[ \text{Ni} + \text{I}_2 \rightarrow \text{NiI}_2 \]

Alternatively, it can be prepared by the reaction of nickel(II) compounds, such as nickel(II) oxide, with hydroiodic acid (HI):

\[ \text{NiO} + 2\text{HI} \rightarrow \text{NiI}_2 + \text{H}_2\text{O} \]

Applications

Nickel(II) iodide finds applications in organic synthesis, where it is used as a catalyst or a reagent in various coupling reactions. It is particularly useful in cross-coupling reactions, which are pivotal in the synthesis of complex organic molecules. Additionally, its use in materials science has been explored, especially in the preparation of nickel-containing materials with specific electronic or magnetic properties.

Safety

Handling nickel(II) iodide requires caution due to its toxic and potentially carcinogenic nature. Inhalation, ingestion, or skin contact should be avoided, and appropriate personal protective equipment (PPE) should be worn when handling the compound. It is also important to work with nickel(II) iodide in a well-ventilated area or under a fume hood to minimize exposure to dust or vapors.

See Also

• Nickel compounds
• Halide
• Organic synthesis
• Catalysis