Iron tetracarbonyl diiodide is the inorganic compound with the formula FeI<sub>2</sub>(CO)<sub>4</sub>. The molecule features four carbonyl ligands and two iodides. It is a low-spin complex of ferrous iron. As confirmed by X-ray crystallography, the compound has cis stereochemistry. It is a black solid that is soluble in dichloromethane and related organic solvents.
It is prepared by the reaction of molecular iodine with iron pentacarbonyl, following a procedure first reported by Hieber and Wirschung in 1940:
Iron tetracarbonyl diiodide reacts with a variety of Lewis bases with displacement of one or two CO ligands. The corresponding dibromide is even more reactive toward Lewis bases.