Iodomethylzinc iodide is the active reagent in the Simmons-Smith reaction.[1] For example, iodomethylzinc iodide, formed in situ from diiodomethane and a zinc-copper couple reacts with cyclohexene to give norcarane (bicyclo[4.1.0]heptane).[1]
Iodomethylzinc iodide may also be generated by the reaction of diazomethane with zinc iodide, or by the reaction of methylene iodide with diethylzinc.[1]