Zinc iodide is the inorganic compound with the formula ZnI<sub>2</sub>. 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.
It can be prepared by the direct reaction of zinc and iodine in water or refluxing ether:
Absent a solvent, the elements do not combine directly at room temperature.
The structure of solid ZnI<sub>2</sub> is unusual relative to the dichloride. While zinc centers are tetrahedrally coordinated, as in ZnCl<sub>2</sub>, groups of four of these tetrahedra share three vertices to form âÂÂsuper-tetrahedraâ of composition {Zn<sub>4</sub>I<sub>10</sub>}, which are linked by their vertices to form a three-dimensional structure. These "super-tetrahedra" are similar to the P<sub>4</sub>O<sub>10</sub> structure.
Molecular ZnI<sub>2</sub> is linear as predicted by VSEPR theory with a Zn-I bond length of 238 pm.
In aqueous solution the following have been detected: Zn(H<sub>2</sub>O)<sub>6</sub><sup>2+</sup>, [ZnI(H<sub>2</sub>O)<sub>5</sub>]<sup>+</sup>, tetrahedral ZnI<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>, ZnI<sub>3</sub>(H<sub>2</sub>O)<sup>âÂÂ</sup>, and ZnI<sub>4</sub><sup>2âÂÂ</sup>.