The standard molar enthalpy of formation of tungsten diiodide is -8.37 kJ/mol. The standard molar enthalpy of formation of tungsten diiodide, Δ_fH_m^θ(WI₂, g, 298 K), is defined as the standard molar enthalpy of formation for the reaction to produce the substance tungsten diiodide (ν_B=+1) from the monomers of the reference state at 298 K. The standard molar enthalpy of formation is -8.37 kJ/mol.

The indirect preparation method of tungsten diiodide does not aim at obtaining the product directly but is a method of preparing other tungsten iodide compounds before preparing the final product. The indirect preparation method develops based on the direct preparation method and chooses tungsten iodide compounds that are easier to prepare relative to tungsten diiodides, such as tungsten triiodide (WI₃) and tetraiodide (WI₄), as intermediate products, to reduce the requirements and uncontrollable factors of the reaction conditions and to improve the yield of tungsten diiodide.

The type of crystal structure of tungsten diiodide is an orthorhombic crystal system, space group Bbem (No. 64), with lattice parameters a = 1258 pm, b = 1259 pm, and c = 1584 pm, and is a crystal cell with hexahedra. Each hexahedron has a tungsten atom in the center surrounded by six iodine atoms, forming a tungsten-iodine octahedron. The tungsten and iodine atoms are located at positions (0,0,0) and (0.5,0.5,0.5), respectively. The crystal has a layered structure with each layer consisting of tungsten-iodine octahedra, with neighboring layers interacting with each other through weak van der Waals forces.

In tungsten diiodide, the tungsten element has a valence of +2, and the iodine element has a valence of -1. Therefore, the quantity ratio of iodine to tungsten in tungsten diiodide is 2:1, which is determined according to the principle of electroneutrality.