Nickel(II) iodide is an inorganic compound with the formula NiI₂. This paramagnetic black solid dissolves readily in water to give bluish-green solutions, from which crystallizes the

aquo complex In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perchlorat ...

i(H₂O)₆₂ (image above). This bluish-green colour is typical of hydrated nickel(II) compounds. Nickel iodides find some applications in

homogeneous catalysis In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysi ...

Structure and synthesis

The anhydrous material crystallizes in the CdCl₂ motif, featuring octahedral coordination geometry at each Ni(II) center. NiI₂ is prepared by

dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...

of the pentahydrate. NiI₂ readily hydrates, and the hydrated form can be prepared by dissolution of nickel oxide, hydroxide, or carbonate in

hydroiodic acid Hydroiodic acid (or hydriodic acid) is an aqueous solution of hydrogen iodide (HI). It is a strong acid, one that is ionized completely in an aqueous solution. It is colorless. Concentrated solutions are usually 48% to 57% HI. Reactions Hy ...

. The anhydrous form can be produced by treating powdered nickel with iodine.

Applications in catalysis

NiI₂ has some industrial applications as a

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

carbonylation Carbonylation refers to reactions that introduce carbon monoxide into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemistry. The term carbony ...

reactions.W. Bertleff, M. Roeper, X. Sava, "Carbonylation" in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH: Weinheim, 2003. . It is also has niche uses as a reagent in organic synthesis, especially in conjunction with

samarium(II) iodide Samarium(II) iodide is an inorganic compound with the formula SmI2. When employed as a solution for organic synthesis, it is known as Kagan's reagent. SmI2 is a green solid and solutions are green as well. It is a strong one-electron reducing a ...

. Like many nickel complexes, those derived from hydrated nickel iodide have been used in cross coupling.

References

{{Iodides Inorganic compounds Iodides Metal halides Nickel compounds