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.

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.

Tungsten hexachloride (WCl₆), as one of the reactants, can be reacted with hydrogen iodide (HI) to prepare tungsten diiodide, but attention should be paid to the temperature of the reaction to reduce the chances of the formation of other products.

There can be two methods of preparing tungsten diiodide using tungsten hexacarbonyl, the main difference between the two being in the choice of temperature.

The high-temperature chemical method of tungsten diiodide is legally produced by the reaction of elemental tungsten and elemental iodine at temperatures between 600 and 800°C: W+I₂→WI₂. Generally, the temperature selected for the reaction is 800°C, and tungsten diiodide is produced using the reaction of tungsten powder with iodine.

There are three direct preparation methods for tungsten diiodide, which are obtained by high-temperature chemotaxis, halide exchange reaction, and reaction of tungsten hexacarbonyl with elemental iodine. Meanwhile, tungsten diiodide can also be obtained by indirect method.

Tungsten diiodide (WI₂) has good stability at room temperature but readily reacts chemically at high temperatures and in the presence of oxygen. Tungsten diiodide is an inorganic compound with the following chemical properties.

Tungsten diiodide is a transition crystal. Transitional crystals are different from many substances in nature with regular geometrical shapes, such as ionic crystals, molecular crystals, atomic crystals, and metal crystals. The inter-particle role of the lattice junctions of the transitional crystals has changed, and the interactions between particles of the crystalline structure and the nature of the crystal between the different types of crystalline forms, which is difficult to be classified as any of the above-mentioned typical crystals, and there are a lot of actual crystals belonging to the transitional crystals.

Tungsten Diiodide is an inorganic compound with the molecular formula WI₂ and a relative molecular mass of 437.7. It is a metal salt of tungsten and hydroiodic acid, characterized by black or dark brown crystals, usually in powder or lump form. Tungsten diiodide has good solubility in alkalis but is insoluble in cold water, ethanol, and carbon disulfide. It has a density of 6.79 g/cm³ and a melting point of about 300°C, which allows it to remain stable at everyday ambient temperatures.

The solubility of tungsten diiodide has no specific pattern. For inorganic solvents, tungsten diiodide is soluble in alkali but insoluble in water at room temperature; for organic solvents, tungsten diiodide is insoluble in ethanol and carbon disulfide (CS₂).