Tin(IV) iodide, also called stannic iodide or tin tetraiodide, is the binary tin–iodine compound with the formula SnI4. It is a covalent molecular halide in which tin is in the +4 oxidation state; this central fact distinguishes it from tin(II) iodide and influences its chemistry. In bulk it forms colored crystalline solids that are noticeably different from the analogous lighter halides.

Structure and physical properties

SnI4 consists of discrete tetrahedral molecules, each containing one tin atom bonded to four iodide ligands. The large, polarizable iodide atoms give the compound significant van der Waals character and relatively low lattice energy compared with tin chlorides or bromides. It is soluble in many nonpolar or weakly polar organic solvents and tends to be volatile for a heavy metal halide. Its appearance, vapor behavior and molecular nature are important when handling or characterizing the substance.

Preparation and reactions

Typical laboratory preparation involves direct combination of elemental tin and iodine under controlled heating, or halide exchange reactions starting from other tin halides. SnI4 can undergo hydrolysis on contact with water and may react with excess iodide to form complex anions in salt form (for example hexaiodostannate(IV) salts). It also participates in halide-exchange and coordination reactions common to tin(IV) chemistry.

Uses, distinctions and notable facts

While not a major industrial commodity, tin(IV) iodide is used as a reagent and synthetic intermediate in research laboratories, particularly when a soluble or molecular tin(IV) source is required. It should be distinguished from tin(II) iodide (SnI2), which has a different structure, oxidation state and reactivity. SnI4 is related to other stannic halides and helps illustrate trends across the halogen series.

Handling and safety

  • SnI4 should be handled in a fume hood to avoid inhalation of vapors and any liberated iodine vapors.
  • It may hydrolyze or decompose to produce corrosive or irritating hydrogen iodide and should be kept dry and stored in appropriate containers.
  • Consult material safety resources and databases for detailed hazard and disposal guidance: see chemical datasheets and supplier recommendations.

For further background on iodide ligands, tin oxidation states and halide complexes consult textbooks on inorganic chemistry or specialized reviews; useful starting points include general references and databases listed under iodide chemistry, oxidation-state conventions, and compound data.