Titanium tetraiodide
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 435047424
| Name = Titanium tetraiodide
| ImageFile = Titanium-tetraiodide-3D-balls.png
| ImageName = Titanium tetraiodide
| ImageFile1 = Titanium tetraiodide.png
| ImageName1 = Titanium tetraiodide
| IUPACName = Titanium(IV) iodide
| OtherNames = Titanium tetraiodide
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 7720-83-4
| PubChem = 111328
| RTECS =
| EINECS = 231-754-0
| SMILES = [Ti](I)(I)(I)I
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 99888
| InChI = 1/4HI.Ti/h4*1H;/q;;;;+4/p-4/rI4Ti/c1-5(2,3)4
| InChIKey = NLLZTRMHNHVXJJ-CDYINDSBAY
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/4HI.Ti/h4*1H;/q;;;;+4/p-4
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = NLLZTRMHNHVXJJ-UHFFFAOYSA-J
}}
|Section2={{Chembox Properties
| Formula = TiI4
| MolarMass = 555.485 g/mol
| Appearance = red-brown crystals
| Density = 4.3 g/cm3
| Solubility = hydrolysis
| Solvent = other solvents
| SolubleOther = soluble in CH2Cl2
CHCl3
CS2
| MeltingPtC = 150
| BoilingPtC = 377
}}
|Section3={{Chembox Structure
| Coordination = tetrahedral
| CrystalStruct = cubic (a = 12.21 Å)
| Dipole = 0 D
}}
|Section7={{Chembox Hazards
| ExternalSDS =
| MainHazards = violent hydrolysis
corrosive
| GHSPictograms = {{GHS05}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314}}
| PPhrases = {{P-phrases|260|264|280|301+330+331|303+361+353|304+340|305+351+338|310|321|363|405|501}}
}}
|Section8={{Chembox Related
| OtherAnions = Titanium(IV) bromide
Titanium(IV) chloride
Titanium(IV) fluoride
| OtherCations = Silicon tetraiodide
Zirconium(IV) iodide
Hafnium(IV) iodide
| OtherCompounds = Titanium(III) iodide
}}
}}
Titanium tetraiodide is an inorganic compound with the formula TiI4. It is a black volatile solid, first reported by Rudolph Weber in 1863.
{{cite journal
| last =Weber |first=R.
| year =1863
| title =Ueber die isomeren Modificationen der Titansäure und über einige Titanverbindungen
| url =http://gallica.bnf.fr/ark:/12148/bpt6k15205n/f305.image.r=poggendorff.langFR
| journal =Annalen der Physik
| volume =120 |issue=10 |pages=287–294
| bibcode =1863AnP...196..287W
| doi =10.1002/andp.18631961003
}} It is an intermediate in the van Arkel–de Boer process for the purification of titanium.
Physical properties
TiI4 is a rare molecular binary metal iodide, consisting of isolated molecules of tetrahedral Ti(IV) centers. The Ti-I distances are 261 pm.
{{cite journal
| last1 =Tornqvist |first1=E. G. M.
| last2 =Libby |first2=W. F.
| year =1979
| title = Crystal Structure, Solubility, and Electronic Spectrum of Titanium Tetraiodide
| journal =Inorganic Chemistry
| volume =18 |issue= 7 |pages= 1792–1796
| doi =10.1021/ic50197a013
}} Reflecting its molecular character, TiI4 can be distilled without decomposition at one atmosphere; this property is the basis of its use in the van Arkel–de Boer process. The difference in melting point between TiCl4 (m.p. -24 °C) and TiI4 (m.p. 150 °C) is comparable to the difference between the melting points of CCl4 (m.p. -23 °C) and CI4 (m.p. 168 °C), reflecting the stronger intermolecular van der Waals bonding in the iodides.
Two polymorphs of TiI4 exist, one of which is highly soluble in organic solvents. In the less soluble cubic form, the Ti-I distances are 261 pm.
Production
Three methods are well known:
1) From the elements, typically using a tube furnace at 425 °C:
{{cite book
| last1 =Lowry |first1=R. N.
| last2 =Fay |first2=R. C.
|chapter=Titanium(IV) Iodide
| year =1967
| title =Inorganic Syntheses
| volume = 10|pages=1–6
| doi =10.1002/9780470132418.ch1
| isbn = 978-0-470-13241-8
}}
::Ti + 2 I2 → TiI4
This reaction can be reversed to produce highly pure films of Ti metal.
{{cite journal
| last1 =Blumenthal |first1=W. B.
| last2 =Smith|first2=H.
| year =1950
| title =Titanium tetraiodide, Preparation and Refining
| journal =Industrial and Engineering Chemistry
| volume =42 |issue=2 |pages=249
| doi =10.1021/ie50482a016
}}
2) Exchange reaction from titanium tetrachloride and HI.
::TiCl4 + 4 HI → TiI4 + 4 HCl
3) Oxide-iodide exchange from aluminium iodide.
::3 TiO2 + 4 AlI3 → 3 TiI4 + 2 Al2O3
Reactions
Like TiCl4 and TiBr4, TiI4 forms adducts with Lewis bases, and it can also be reduced. When the reduction is conducted in the presence of Ti metal, one obtains polymeric Ti(III) and Ti(II) derivatives such as CsTi2I7 and the chain CsTiI3, respectively.
{{cite journal
| last1 =Jongen |first1=L.
| last2 =Gloger |first2=T.
| last3 =Beekhuizen |first3=J.
| last4 =Meyer |first4=G.
| year =2005
| title =Divalent Titanium: The Halides ATiX3 (A = K, Rb, Cs; X = Cl, Br, I)
| journal =Zeitschrift für anorganische und allgemeine Chemie
| volume =631 |issue=2–3 |pages=582
| doi =10.1002/zaac.200400464
}}
TiI4 exhibits extensive reactivity toward alkenes and alkynes resulting in organoiodine derivatives. It also effects pinacol couplings and other C-C bond-forming reactions.
{{cite journal
| last1 =Shimizu |first1=M.
| last2 = Hachiya |first2=I.
| year =2014
| title =Chemoselective Reductions and Iodinations using Titanium Tetraiodide
| journal =Tetrahedron Letters
|volume=55
| issue =17 |pages=2781–2788
| doi =10.1016/j.tetlet.2014.03.052
| doi-access =free
}}
References
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{{Titanium compounds}}
{{Iodides}}
{{DEFAULTSORT:Titanium Tetraiodide}}