Zinc iodide

Zinc iodide is a chemical compound of zinc and iodine, ZnI₂. The anhydrous form is white and readily absorbs water from the atmosphere. It can be prepared by the direct reaction of zinc and iodine in refluxing ether. or by reacting zinc with iodine in aqueous solution:

Zn + I₂→ ZnI₂

At 1150 °C, zinc iodide vapour dissociates into zinc and iodine.
In aqueous solution the following have been detected, octahedral Zn(H₂O)₆²⁺, [ZnI(H₂O)₅]⁺ and tetrahedral ZnI₂(H₂O)₂, ZnI₃(H₂O)⁻ and ZnI₄²⁻.

The structure of crystalline ZnI₂ is unusual, and while zinc atoms 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. These "super-tetrahedra" are similar to the P₄O₁₀ structure. Molecular ZnI₂ is linear as predicted by VSEPR theory with a Zn-I bond length of 238 pm.