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Zinc iodide
Names
	IUPAC name Zinc iodide
	Other names Zinc(II) iodide
Identifiers
CAS Number	10139-47-6 ;
3D model (JSmol)	Interactive image;
ChemSpider	59657 ;
ECHA InfoCard	100.030.347
PubChem CID	66278;
UNII	762R7A0O0B ;
CompTox Dashboard (EPA)	DTXSID5064968 ;
	InChI InChI=1S/2HI.Zn/h21H;/q;;+2/p-2 Key: UAYWVJHJZHQCIE-UHFFFAOYSA-L ; InChI=1/2HI.Zn/h21H;/q;;+2/p-2 Key: UAYWVJHJZHQCIE-NUQVWONBAB;
	SMILES I[Zn]I;
Properties
Chemical formula	ZnI2
Molar mass	319.19 g/mol
Appearance	white solid
Density	4.74 g/cm3
Melting point	446 °C (835 °F; 719 K)
Boiling point	1,150 °C (2,100 °F; 1,420 K) decomposes
Solubility in water	450 g/100mL (20 °C)
Magnetic susceptibility (χ)	−98.0·10−6 cm3/mol
Structure
Crystal structure	Tetragonal, tI96
Space group	I41/acd, No. 142
Hazards
Flash point	625 °C (1,157 °F; 898 K)
Safety data sheet (SDS)	External MSDS
Related compounds
Other anions	Zinc fluoride; Zinc chloride; Zinc bromide
Other cations	Cadmium iodide; Mercury(I) iodide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Zinc iodide is the inorganic compound with the formula ZnI₂. It exists both in anhydrous form and as a dihydrate. Both are white and readily absorb water from the atmosphere. It has no major application.

Preparation

It can be prepared by the direct reaction of zinc and iodine in water^[1] or in refluxing ether.^[2] or by treating zinc with iodine in aqueous solution:^[3]

Zn + I₂ → ZnI₂

Structure as solid, gas, and in solution

The structure of solid ZnI₂ is unusual relative to the dichloride. While zinc centers are tetrahedrally coordinated, as in ZnCl₂, groups of four of these tetrahedra share three vertices to form “super-tetrahedra” of composition {Zn₄I₁₀}, which are linked by their vertices to form a three-dimensional structure.^[4] These "super-tetrahedra" are similar to the P₄O₁₀ structure.^[4]^[5]

Molecular ZnI₂ is linear as predicted by VSEPR theory with a Zn-I bond length of 238 pm.^[4]

In aqueous solution the following have been detected: Zn(H₂O)₆²⁺, [ZnI(H₂O)₅]⁺, tetrahedral ZnI₂(H₂O)₂, ZnI₃(H₂O)⁻, and ZnI₄²⁻.^[6]

Applications

Zinc iodide is often used as an x-ray opaque penetrant in industrial radiography to improve the contrast between the damage and intact composite.^[7]^[8]
United States patent 4,109,065 ^[9] describes a rechargeable aqueous zinc-halogen cell that includes an aqueous electrolytic solution containing a zinc salt selected from the class consisting of zinc bromide, zinc iodide, and mixtures thereof, in both positive and negative electrode compartments.
In combination with osmium tetroxide, ZnI₂ is used as a stain in electron microscopy.^[10]
As a Lewis acid, zinc iodide catalyzes for the conversion of methanol to triptane and hexamethylbenzene.^[11]

References

^ F. Wagenknecht; R. Juza (1963). "Zinc iodide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY, NY: Academic Press. p. 1073.
^ Eagleson, M. (1994). Concise Encyclopedia Chemistry. Walter de Gruyter. ISBN 3-11-011451-8.
^ DeMeo, S. (1995). "Synthesis and Decomposition of Zinc Iodide: Model Reactions for Investigating Chemical Change in the Introductory Laboratory". Journal of Chemical Education. 72 (9): 836. Bibcode:1995JChEd..72..836D. doi:10.1021/ed072p836.
^ ^a ^b ^c Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford Science Publications. ISBN 0-19-855370-6.
^ Fourcroy, P. H.; Carré, D.; Rivet, J. (1978). "Structure Cristalline de l'Iodure de Zinc ZnI₂". Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry. 34 (11): 3160–3162. Bibcode:1978AcCrB..34.3160F. doi:10.1107/S0567740878010390.
^ Wakita, H.; Johansson, G.; Sandström, M.; Goggin, P. L.; Ohtaki, H. (1991). "Structure determination of zinc iodide complexes formed in aqueous solution". Journal of Solution Chemistry. 20 (7): 643–668. doi:10.1007/BF00650714. S2CID 97496242.
^ Baker, A.; Dutton, S.; Kelly, D., eds. (2004). Composite Materials for Aircraft Structures (2nd ed.). AIAA (American Institute of Aeronautics & Astronautics). ISBN 1-56347-540-5.
^ Ezrin, M. (1996). Plastics Failure Guide. Hanser Gardner Publications. ISBN 1-56990-184-8.
^ US patent 4109065, Will, F. G.; Secor, F. W., "Rechargeable aqueous zinc-halogen cell", issued 1978-08-22, assigned to General Electric
^ Hayat, M. A. (2000). Principles and Techniques of Electron Microscopy: Biological Applications (4th ed.). Cambridge University Press. ISBN 0-521-63287-0.
^ Bercaw, John E.; Diaconescu, Paula L.; Grubbs, Robert H.; Kay, Richard D.; Kitching, Sarah; Labinger, Jay A.; Li, Xingwei; Mehrkhodavandi, Parisa; Morris, George E. (2006-11-01). "On the Mechanism of the Conversion of Methanol to 2,2,3-Trimethylbutane (Triptane) over Zinc Iodide". The Journal of Organic Chemistry. 71 (23): 8907–8917. doi:10.1021/jo0617823. ISSN 0022-3263. PMID 17081022.