Hafnium(III) iodide
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| ImageFile1 = HfI3 unit cell.png
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| ImageName1 = Ball-and-stick model of the unit cell of the crystal structure of hafnium(III) iodide
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| Name = Hafnium(III) iodide
| IUPACName = Hafnium triiodide
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|Section1={{Chembox Identifiers
| CASNo = 13779-73-2
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| SMILES = [I-].[I-].[I-].[Hf+3]
| PubChem = 161242838
| PubChem_Comment=charge error
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| StdInChI=1S/Hf.3HI/h;3*1H/q+3;;;/p-3
| StdInChIKey = VAFXHNPAMHBKMS-UHFFFAOYSA-K
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|Section2={{Chembox Properties
| Hf=1 | I=3
| Appearance = black crystals{{ cite book | title = CRC Handbook of Chemistry and Physics | edition = 93rd | publisher = CRC Press | year = 2013 | editor = William M. Haynes | page = 4–66 | isbn = 978-1466571143 }}
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| MeltingPt_notes = decomposes
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|Section3={{Chembox Structure
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|Section4={{Chembox Thermochemistry
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|Section7={{Chembox Hazards
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|Section8={{Chembox Related
| OtherCompounds = Hafnium(IV) iodide
| OtherAnions = Hafnium(III) chloride
Hafnium(III) bromide
| OtherCations = Titanium(III) iodide
Zirconium(III) iodide
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Hafnium(III) iodide is an inorganic compound of hafnium and iodine with the formula Hf I3. It is a black solid.{{Greenwood&Earnshaw2nd|page=965}}
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.
: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.{{ cite journal | title = Lower halides of hafnium. Nonstoichiometric hafnium triiodide phase | first1 = Arthur W. | last1 = Struss | first2 = John D. | last2 = Corbett | journal = Inorg. Chem. | year = 1969 | volume = 8 | issue = 2 | pages = 227–232 | doi = 10.1021/ic50072a009 }}{{ cite book | first1 = R. J. H. | last1 = Clark | first2 = D. C. | last2 = Bradley | first3 = P. | last3 = Thornton | title = The Chemistry of Titanium, Zirconium and Hafnium Pergamon Texts in Inorganic Chemistry | publisher = Elsevier | isbn = 978-1-4831-5921-8 | year = 2013 | page = 432 }}
Structure and bonding
Hafnium(III) iodide adopts the same crystal structure as zirconium(III) iodide.{{ cite book | first1 = A. F. | last1 = Wells | title = Structural Inorganic Chemistry | edition = 5th | year = 1984 | publisher = Oxford University Press | isbn = 978-0-19-965763-6 | pages = 418–419 }} This is very similar to the β-TiCl3 structure. The structure is based on hexagonal close packing of iodide ions with one third of the octahedral interstices occupied by Hf3+ ions. It consists of parallel chains of face-sharing {HfI6} octahedra.
Hafnium(III) iodide has a lower magnetic moment than is expected for the d1 metal ion Hf3+, indicating non-negligible Hf–Hf bonding. The Hf–Hf separation was originally reported to be 3.295 Å,{{ cite journal | title = Structural Studies of Zirconium Trihalides and Hafnium Triiodide | first1 = Lawrence F. | last1 = Dahl | first2 = Tao-I | last2 = Chiang | first3 = Pyrtle W. | last3 = Seabaugh | first4 = Edwin M. | last4 = Larsen | journal = Inorg. Chem. | year = 1964 | volume = 3 | issue = 9 | pages = 1236–1242 | doi = 10.1021/ic50019a008 }} but a subsequent study of nonstoichiometric hafnium(III) iodide indicated a lower symmetry structure.
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.
References
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{{Hafnium compounds}}
{{Iodides}}
{{DEFAULTSORT:Hafnium(Iii) Iodide}}