Tungsten(IV) iodide is a binary inorganic compound of tungsten metal and iodine with the chemical formula .
Reaction of tungsten(VI) chloride with gaseous hydrogen iodide or concentrated hydroiodic acid:
Reaction of tungsten(IV) chloride with hydroiodic acid:
Tungsten(IV) iodide forms black crystals of the triclinic crystal system. Insoluble in cold water, diethyl ether, and chloroform. It dissolves in ethanol.
The compound decomposes when heated in vacuum:
It hydrolyzes in hot water:
Reacts with chlorine and bromine: