Hafnium(III) iodide
Ball-and-stick model of the unit cell of the crystal structure of hafnium(III) iodide
Names
IUPAC name
Hafnium triiodide
Identifiers
3D model (JSmol)
  • InChI=1S/Hf.3HI/h;3*1H/q+3;;;/p-3
    Key: VAFXHNPAMHBKMS-UHFFFAOYSA-K
  • [I-].[I-].[I-].[Hf+3]
Properties
HfI3
Molar mass 559.20 g·mol−1
Appearance black crystals[1]
Melting point decomposes
Related compounds
Other anions
 Hafnium(III) chloride
Hafnium(III) bromide
Other cations
 Titanium(III) iodide
Zirconium(III) iodide
Related compounds
 Hafnium(IV) iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Hafnium(III) iodide is an inorganic compound of hafnium and iodine with the formula Hf I3. It is a black solid.[2]

Preparation

Like other group 4 trihalides, hafnium(III) iodide can be prepared from hafnium(IV) iodide by high-temperature reduction with hafnium metal, although incomplete reaction and contamination of the product with excess metal often occurs.[2]

3 Hf I4 + Hf → 4 Hf I3

Other metals can be used as the reducing agent, for example aluminium. The product is often nonstoichiometric, with the compositions Hf I3.2–3.3 and Hf I3.0–3.5 reported.[3][4]

Structure and bonding

Hafnium(III) iodide adopts the same crystal structure as zirconium(III) iodide.[5] This is very similar to the β-TiCl3 structure.[2] The structure is based on hexagonal close packing of iodide ions with one third of the octahedral interstices occupied by Hf3+ ions.[2] It consists of parallel chains of face-sharing {HfI6} octahedra.[5]

Hafnium(III) iodide has a lower magnetic moment than is expected for the d1 metal ion Hf3+, indicating non-negligible Hf–Hf bonding.[2] The Hf–Hf separation was originally reported to be 3.295 Å,[6] but a subsequent study of nonstoichiometric hafnium(III) iodide indicated a lower symmetry structure.[3]

Reactivity

Like the chloride and bromide, hafnium(III) iodide is a powerful enough reducing agent to reduce water and therefore does not have any aqueous chemistry.[2]

References

  1. ^ William M. Haynes, ed. (2013). CRC Handbook of Chemistry and Physics (93rd ed.). CRC Press. p. 4–66. ISBN 978-1466571143.
  2. ^ a b c d e f Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 965. ISBN 978-0-08-037941-8.
  3. ^ a b Struss, Arthur W.; Corbett, John D. (1969). "Lower halides of hafnium. Nonstoichiometric hafnium triiodide phase". Inorg. Chem. 8 (2): 227–232. doi:10.1021/ic50072a009.
  4. ^ Clark, R. J. H.; Bradley, D. C.; Thornton, P. (2013). The Chemistry of Titanium, Zirconium and Hafnium Pergamon Texts in Inorganic Chemistry. Elsevier. p. 432. ISBN 978-1-4831-5921-8.
  5. ^ a b Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. pp. 418–419. ISBN 978-0-19-965763-6.
  6. ^ Dahl, Lawrence F.; Chiang, Tao-I; Seabaugh, Pyrtle W.; Larsen, Edwin M. (1964). "Structural Studies of Zirconium Trihalides and Hafnium Triiodide". Inorg. Chem. 3 (9): 1236–1242. doi:10.1021/ic50019a008.
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