Hafnium(IV) iodide

Hafnium(IV) iodide 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.^[2] It is an intermediate in the crystal bar process for producing hafnium metal.

Hafnium(IV) iodide

Names
IUPAC name Hafnium(IV) iodide
Other names hafnium tetraiodide, tetraiodohafnium
Identifiers
CAS Number	13777-23-6
3D model (JSmol)	Interactive image
ChemSpider	75548
ECHA InfoCard	100.150.349
EC Number	621-502-1
PubChem CID	83726
CompTox Dashboard (EPA)	DTXSID7065629
InChI InChI=1S/Hf.4HI/h;4*1H/q+4;;;;/p-4 Key: YCJQNNVSZNFWAH-UHFFFAOYSA-J
SMILES I[Hf](I)(I)I
Properties
Chemical formula	HfI4
Molar mass	686.11[1]
Appearance	red-orange[1]
Density	5.60 g/cm3[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
Related compounds
Other anions	Hafnium(IV) fluoride Hafnium(IV) chloride Hafnium(IV) bromide
Other cations	Titanium(IV) iodide Zirconium(IV) iodide
Related compounds	Hafnium(III) iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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.^[2]

References

1. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, Florida: CRC Press. p. 4.66. ISBN 1-4398-5511-0.
2. Krebs, B.; Sinram, D. (1980). "Hafniumtetrajodid HfI₄: Struktur und eigenschaften. Ein neuer AB₄-strukturtyp". Journal of the Less Common Metals. 76 (1–2): 7–16. doi:10.1016/0022-5088(80)90005-3.