Hafnium tetraiodide

Hafnium tetraiodide

Identifiers
CAS Number	13777-23-6
Properties
Chemical formula	HfI4
Molar mass	686.11[1]
Appearance	red-orange[1]
Density	5.60 g/cm^3[1]
Melting point	449 °C (840 °F; 722 K)[1]
Boiling point	394 °C (741 °F; 667 K)[1] (sublimes)
Structure
Crystal structure	Monoclinic, mS40
Space group	C2/c, No. 15[2]
Lattice constant	a = 1.1787 nm, b = 1.1801 nm, c = 1.2905 nm
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Hafnium tetraiodide is the inorganic compound with the formula HfI₄. It is a red-orange, moisture sensitive, sublimable solid that is produced by heating a mixture of hafnium with excess iodine.^[3] It is an intermediate in the crystal bar process for producing hafnium metal.

In this compound, the hafnium centers adopt octahedral coordination geometry. Like most binary metal halides, the compound is a polymeric. It is one-dimensional polymer consisting of chains of edge-shared bioctahedral Hf₂I₈ subunits, similar to the motif adopted by HfCl₄. The nonbridging iodide ligands have shorter bonds to Hf than the bridging iodide ligands.^[3]

References

1. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.66. ISBN 1439855110.
2. Krebs, B.; Sinram, D. (1980). "Hafniumtetrajodid HfI₄: Struktur und eigenschaften. Ein neuer AB₄-strukturtyp". Journal of the Less Common Metals 76: 7. doi:10.1016/0022-5088(80)90005-3.
3. Krebs, B.; Sinram, D. (1980). "Hafniumtetrajodid HfI₄: Struktur und eigenschaften. Ein neuer AB₄-strukturtyp". Journal of the Less Common Metals 76: 7. doi:10.1016/0022-5088(80)90005-3.