Hafnium(III) iodide

Names
IUPAC name

Hafnium triiodide

Identifiers

CAS Number

* 13779-73-2 Y

3D model (JSmol)

* Interactive image

PubChem CID

* 161242838 charge error

InChI

* InChI=1S/Hf.3HI/h;3*1H/q+3;;;/p-3

Key: VAFXHNPAMHBKMS-UHFFFAOYSA-K

SMILES

* [I-].[I-].[I-].[Hf+3]

Properties

Chemical formula

| 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).

Infobox references

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

## Contents

* 1 Preparation
* 2 Structure and bonding
* 3 Reactivity
* 4 References

## 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. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 965. ISBN 978-0-08-037941-8.
3. ↑ 3.0 3.1 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. ↑ 5.0 5.1 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.

* v
* t
* e

Hafnium compounds

Hf(II)|

* HfB2

Hf(IV)|

* HfC
* HfBr4
* HfCl4
* HfF4
* HfI4
* Hf(C5H7O2)4
* HfO2
* HfSiO4
* HfS2
* Ta4HfC5

HI |  |  |  | He

|
|
|
|

LiI | BeI2 | BI3 | CI4 | NI3 | I2O4,
I2O5,
I4O9 | IF,
IF3,
IF5,
IF7 | Ne
NaI | MgI2 | AlI3 | SiI4 | PI3,
P2I4 | S  | ICl,
ICl3 | Ar
KI | CaI2 | Sc  | TiI4 | VI3 | CrI3 | MnI2 | FeI2 | CoI2 | NiI2 | CuI | ZnI2 | Ga2I6 | GeI2,
GeI4 | AsI3 | Se  | IBr | Kr
RbI | SrI2 | YI3 | ZrI4 | NbI5 | Mo  | Tc  | Ru  | Rh  | Pd  | AgI | CdI2 | InI3 | SnI4,
SnI2 | SbI3 | TeI4 | I  | Xe
CsI | BaI2 |  | HfI4 | TaI5 | W  | Re  | Os  | Ir  | Pt  | AuI | Hg2I2,
HgI2 | TlI | PbI2 | BiI3 | Po  | AtI | Rn
Fr  | RaI2 |  | Rf  | Db  | Sg  | Bh  | Hs  | Mt  | Ds  | Rg  | Cn  | Nh  | Fl  | Mc  | Lv  | Ts  | Og
| ↓  |  |
La  | Ce  | Pr  | Nd  | Pm  | SmI2 | Eu  | Gd  | TbI3 | Dy  | Ho  | Er  | Tm  | Yb  | Lu
Ac  | ThI4 | Pa  | UI3,
UI4 | Np  | Pu  | Am  | Cm  | Bk  | Cf  | EsI3 | Fm  | Md  | No  | Lr

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