Editing Titanium tetrachloride

{{short description|Inorganic chemical compound}}
{{Chembox
| Watchedfields = changed
| verifiedrevid = 470610882
| ImageFile= Sample of Titanium tetrachloride 01.jpg
| ImageSize = 250
| ImageFile1 = Titanium-tetrachloride-3D-vdW.png
| ImageFile1_Ref = {{chemboximage|correct|??}}
| ImageSize1 = 121
| ImageName1 = Spacefill model of titanium tetrachloride
| IUPACName = Titanium(IV) chloride
| OtherNames = Titanium tetrachloride <br/> Tetrachlorotitanium 
|Section1={{Chembox Identifiers
| CASNo = 7550-45-0
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 8O3PJE5T7Q
| PubChem = 24193
| ChEBI = 231499
| ChemSpiderID = 22615
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 231-441-9
| UNNumber = 1838
| MeSHName = Titanium+tetrachloride
| RTECS = XR1925000
| SMILES = Cl[Ti](Cl)(Cl)Cl
| StdInChI = 1S/4ClH.Ti/h4*1H;/q;;;;+4/p-4
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChI = 1/4ClH.Ti/h4*1H;/q;;;;+4/p-4/rCl4Ti/c1-5(2,3)4
| StdInChIKey = XJDNKRIXUMDJCW-UHFFFAOYSA-J
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| InChIKey = XJDNKRIXUMDJCW-FOGBWSKZAG
}}
|Section2={{Chembox Properties
| Formula = {{chem2|TiCl4}}
| MolarMass = 189.679 g/mol
| Appearance = Colourless liquid
| Odor = penetrating acid odor
| Density = 1.726 g/cm<sup>3</sup>
| Solubility = reacts (exothermic hydrolysis)<ref>{{cite journal|last1=Eremenko|first1=B. V.|last2=Bezuglaya|first2=T. N.|last3=Savitskaya|first3=A. N.|last4=Malysheva|first4=M. L.|last5=Kozlov|first5=I. S.|last6=Bogodist|first6=L. G.|title=Stability of Aqueous Dispersions of the Hydrated Titanium Dioxide Prepared by Titanium Tetrachloride Hydrolysis|journal=Colloid Journal|date=2001|volume=63|issue=2|pages=173–178|doi=10.1023/A:1016673605744|s2cid=93971747}}</ref>
| SolubleOther = soluble in [[dichloromethane]],<ref>{{cite web|title=titanium(IV) chloride, 1M soln. in dichloromethane|url=https://www.alfa.com/en/catalog/H31830/|website=Alfa Aesar|access-date=7 March 2018}}</ref> [[toluene]],<ref>{{cite web|title=Titanium(IV) chloride solution 1.0 M in toluene|url=https://www.sigmaaldrich.com/catalog/product/sigald/345695|website=Sigma-Aldrich|access-date=7 March 2018}}</ref> [[pentane]]<ref>{{cite web|last1=Butts|first1=Edward H De|title=patent US3021349A|url=https://patents.google.com/patent/US3021349}}</ref>
| MeltingPtC = -24.1
| BoilingPtC = 136.4
| VaporPressure = 1.3 kPa (20&nbsp;°C)
| Viscosity = 827 μPa s
| RefractIndex = 1.61 (10.5&nbsp;°C)
| MagSus = &minus;54.0·10<sup>−6</sup> cm<sup>3</sup>/mol
}}
|Section3={{Chembox Structure
| Coordination = Tetragonal
| MolShape = Tetrahedral
| Dipole = 0 D
}}
|Section4={{Chembox Thermochemistry
| DeltaHf = −763&nbsp;kJ·mol<sup>−1</sup><ref name=b1>{{cite book| last= Zumdahl |first=Steven S.|title =Chemical Principles |edition=6th | publisher = Houghton-Mifflin| year = 2009| isbn = 978-0-618-94690-7|page=A23}}</ref>
| Entropy = 355&nbsp;J·mol<sup>−1</sup>·K<sup>−1</sup><ref name=b1/>
 }}
|Section5={{Chembox Hazards
| MainHazards = Toxic, corrosive, reacts with water to release [[hydrochloric acid|HCl]]
| ExternalSDS = [http://www.sciencelab.com/msds.php?msdsId=9925270 MSDS]
| Hazards_ref=<ref>{{cite web |title=Classifications - CL Inventory |url=https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/details/3837 |website=echa.europa.eu}}</ref>
| GHSPictograms = {{GHS05}}{{GHS06}}{{GHS07}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314|317|330|335|370|372}}
| PPhrases = {{P-phrases|280|301+330+331|304+340|305+351+338|308+310}}
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 2
| NFPA-S = W
}}
|Section8={{Chembox Related
| OtherAnions = [[Titanium(IV) bromide]] <br/> [[Titanium(IV) fluoride]]<br/> [[Titanium(IV) iodide]]
| OtherCations = [[Hafnium(IV) chloride]] <br/> [[Zirconium(IV) chloride]]
| OtherCompounds = [[Titanium(II) chloride]] <br/> [[Titanium(III) chloride]]
}}
}}
[[File:Titanium tetrachloride phases.jpg|alt=clear crystals under a clear liquid at the bottom of a glass flask|right|thumb|Crystals of frozen titanium tetrachloride melting into the liquid]]
'''Titanium tetrachloride''' is the [[inorganic compound]] with the [[chemical formula|formula]] {{chem2|TiCl4}}. It is an important intermediate in the production of [[titanium]] metal and the pigment [[titanium dioxide]]. {{chem2|TiCl4}} is a [[Volatility (chemistry)|volatile]] liquid. Upon contact with humid air, it forms thick clouds of [[titanium dioxide]] ({{chem2|TiO2}}) and [[hydrochloric acid]], a reaction that was formerly exploited for use in smoke machines. It is sometimes referred to as "tickle" or "tickle 4", as a phonetic representation of the symbols of its molecular formula ({{chem2|TiCl4}}).<ref>[http://chlorine.americanchemistry.com/Science-Center/Chlorine-Compound-of-the-Month-Library/Titanium-Tetrachloride-Stepping-Stone-to-Amazing-Technology] {{Webarchive|url=https://web.archive.org/web/20130217024155/http://chlorine.americanchemistry.com/Science-Center/Chlorine-Compound-of-the-Month-Library/Titanium-Tetrachloride-Stepping-Stone-to-Amazing-Technology|date=2013-02-17}} [[American Chemistry Council]] – "Titanium Tetrachloride: Stepping Stone to Amazing Technology"</ref><ref>{{cite web |url=http://avogadro.chem.iastate.edu/MSDS/TiCl4.htm |title=Archived copy |access-date=2013-04-10 |url-status=dead |archive-url=https://web.archive.org/web/20140319063249/http://avogadro.chem.iastate.edu/MSDS/TiCl4.htm |archive-date=2014-03-19 }} [[Iowa State University]] – "Chemistry Material Safety Data Sheets"</ref>

==Properties and structure==
{{chem2|TiCl4}} is a dense, colourless liquid, although crude samples may be yellow or even red-brown. It is one of the rare transition metal halides that is a liquid at room temperature, [[vanadium tetrachloride|{{chem2|VCl4}}]] being another example. This property reflects the fact that molecules of {{chem2|TiCl4}} weakly self-associate. Most metal chlorides are [[polymer]]s, wherein the chloride atoms bridge between the metals. Its [[melting point]] is similar to that of [[Carbon tetrachloride|{{chem2|CCl4}}]].<ref name="Earnshaw1997">{{cite book|last1=Earnshaw|first1=A.|last2=Greenwood|first2=N.|year=1997|title=Chemistry of the Elements|edition=2nd|publisher=[[Butterworth-Heinemann]]}}</ref><ref name="ullmann" />

{{chem2|Ti(4+)}} has a "closed" electronic shell, with the same number of electrons as the noble gas [[argon]]. The [[tetrahedral]] structure for {{chem2|TiCl4}} is consistent with its description as a d<sup>0</sup> metal center ({{chem2|Ti(4+)}}) surrounded by four identical ligands. This configuration leads to highly [[symmetry|symmetrical]] structures, hence the tetrahedral shape of the molecule. {{chem2|TiCl4}} adopts similar structures to [[Titanium tetrabromide|{{chem2|TiBr4}}]] and [[Titanium tetraiodide|{{chem2|TiI4}}]]; the three compounds share many similarities. {{chem2|TiCl4}} and {{chem2|TiBr4}} react to give mixed halides {{chem2|TiCl_{4−''x''}Br_{''x''}|}}, where ''x'' = 0, 1, 2, 3, 4. Magnetic resonance measurements also indicate that halide exchange is also rapid between {{chem2|TiCl4}} and {{chem2|VCl4}}.<ref>{{cite journal|first1= S. P. |last1=Webb |first2=M. S. |last2=Gordon |title= Intermolecular Self-Interactions of the Titanium Tetrahalides TiX<sub>4</sub> (X = F, Cl, Br)|journal=[[J. Am. Chem. Soc.]]|year=1999|volume=121| pages=2552–2560 |doi=10.1021/ja983339i|issue= 11|bibcode=1999JAChS.121.2552W |url=https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1355&context=chem_pubs|url-access=subscription}}</ref>

{{chem2|TiCl4}} is soluble in [[toluene]] and [[chlorocarbon]]s. Certain [[arene]]s form complexes of the type {{chem2|[(C6R6)TiCl3]+}}.<ref name="TiCplx" /> {{chem2|TiCl4}} reacts [[exothermic]]ally with donor [[solvent]]s such as [[THF]] to give hexacoordinated [[adduct]]s.<ref>{{cite book|first1= L. E. |last1=Manzer|chapter=31. Tetragtdrfuran Complexes of Selected Early Transition Metals |title= Inorganic Syntheses|year=1982| volume=21| pages=135–40|doi=10.1002/9780470132524.ch31|isbn= 978-0-470-13252-4}}</ref> Bulkier [[ligand]]s (L) give pentacoordinated [[adduct]]s {{chem2|TiCl4L}}.

==Production==
{{chem2|TiCl4}} is produced by the [[chloride process]], which involves the [[redox|reduction]] of titanium oxide ores, typically [[ilmenite]] ({{chem2|FeTiO3}}), with [[carbon]] under flowing [[chlorine]] at 900&nbsp;°C. Impurities are removed by [[distillation]].<ref name="ullmann">{{cite encyclopedia|author1=Heinz Sibum |author2=Volker Güther |author3=Oskar Roidl |author4=Fathi Habashi |author5=Hans Uwe Wolf |author6=Carsten Siemers |title=Titanium, Titanium Alloys, and Titanium Compounds
|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |publisher=Wiley-VCH |location=Weinheim |date=2017 |pages=1–35 |doi=10.1002/14356007.a27_095.pub2|isbn=978-3-527-30673-2 }}</ref>

:{{chem2|2 FeTiO3 + 7 Cl2 + 6 C → 2 TiCl4 + 2 FeCl3 + 6 CO}}

The coproduction of [[Iron(III) chloride|{{chem2|FeCl3}}]] is undesirable, which has motivated the development of alternative technologies. Instead of directly using ilmenite, "rutile slag" is used. This material, an impure form of {{chem2|TiO2}}, is derived from ilmenite by removal of iron, either using carbon reduction or extraction with [[sulfuric acid]]. Crude {{chem2|TiCl4}} contains a variety of other volatile halides, including [[vanadyl chloride]] ({{chem2|VOCl3}}), [[silicon tetrachloride]] ({{chem2|SiCl4}}), and [[tin tetrachloride]] ({{chem2|SnCl4}}), which must be separated.<ref name="ullmann" />

==Applications==

===Production of titanium metal===
The world's supply of titanium metal, about 250,000 tons per year, is made from {{chem2|TiCl4}}. The conversion involves the reduction of the tetrachloride with [[magnesium]] metal. This procedure is known as the [[Kroll process]]:<ref name=Ull/>

:{{chem2|2 Mg + TiCl4 → 2 MgCl2 + Ti}}

In the [[Hunter process]], liquid [[sodium]] is the [[reducing agent]] instead of magnesium.<ref>{{Cite encyclopedia |entry=Hunter process |dictionary=A Dictionary of Chemical Engineering |date=2014 |url=http://www.oxfordreference.com/view/10.1093/acref/9780199651450.001.0001/acref-9780199651450-e-1447 |url-access=subscription |language=en|doi=10.1093/acref/9780199651450.001.0001|last1=Schaschke |first1=Carl |publisher=Oxford University Press |isbn=978-0-19-965145-0 }}</ref>

===Production of titanium dioxide===
Around 90% of the {{chem2|TiCl4}} production is used to make the pigment [[titanium dioxide]] ({{chem2|TiO2}}). The conversion involves [[hydrolysis]] of {{chem2|TiCl4}}, a process that forms [[hydrogen chloride]]:<ref name=Ull>{{cite encyclopedia|first=Hans G. |last=Völz |display-authors=etal |title=Inorganic Pigments|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |publisher=Wiley-VCH |location=Weinheim |date=2006 |doi=10.1002/14356007.n20_n04|chapter=Pigments, Inorganic |isbn=978-3-527-30673-2 }}</ref>

:{{chem2|TiCl4 + 2 H2O → TiO2 + 4 HCl}}

In some cases, {{chem2|TiCl4}} is oxidised directly with [[oxygen]]:

:{{chem2|TiCl4 + O2 → TiO2 + 2 Cl2}}

===Smoke screens===
It has been used to produce [[smoke screen]]s since it produces a heavy, white smoke that has little tendency to rise. "Tickle" was the standard means of producing on-set smoke effects for motion pictures, before being phased out in the 1980s due to concerns about [[Hydrochloric acid|hydrated HCl]]'s effects on the respiratory system.{{Citation needed|date=April 2025}}

==Chemical reactions==
Titanium tetrachloride is a versatile reagent that forms diverse derivatives including those illustrated below.<ref name="organoti">{{cite book |last1=Reetz |first1=Manfred T. |title=Organotitanium reagents in organic synthesis |date=1986 |publisher=Springer-Verl |location=Berlin Heidelberg New York Tokyo |isbn=0-387-15784-0 |edition=Reactivity and Structure Concepts in Organic Chemistry, Vol 24}}</ref>

[[Image:TiCl4cmpds.png|center|500px]]

===Alcoholysis and related reactions===
A characteristic reaction of {{chem2|TiCl4}} is its easy [[hydrolysis]], signaled by the release of [[hydrochloric acid|HCl]] vapors and [[titanium oxide]]s and [[oxychloride]]s. Titanium tetrachloride has been used to create naval [[smoke-screen|smokescreens]], as the hydrochloric acid aerosol and titanium dioxide that is formed scatter light very efficiently. This smoke is corrosive, however.<ref name="ullmann" />

Alcohols react with {{chem2|TiCl4}} to give alkoxides with the formula {{chem2|[Ti(OR)4]_{''n''}|}} (R = [[alkyl]], ''n'' = 1, 2, 4). As indicated by their formula, these [[alkoxide]]s can adopt complex structures ranging from monomers to tetramers. Such compounds are useful in [[materials science]] as well as [[organic synthesis]]. A well known derivative is [[titanium isopropoxide]], which is a monomer. [[Titanium bis(acetylacetonate)dichloride]] results from treatment of titanium tetrachloride with excess [[acetylacetone]]:<ref name=IS>{{cite journal|first1=C. A. |last1=Wilkie |first2=G. |last2=Lin |first3=D. T. |last3=Haworth |title=''Cis''-[Dihalobis(2,4-Pentaedionato)Titanium(IV)] Complexes |journal=[[Inorganic Syntheses|Inorg. Synth.]]|year= 1979 |volume=19 |pages=145–148 |doi=10.1002/9780470132500.ch33|isbn=978-0-470-13250-0 }}</ref>
:{{chem2|TiCl4 + 2 [[Acetylacetone|Hacac]] → Ti([[Acetylacetone|acac]])2Cl2 + 2 HCl}}

Organic [[amine]]s react with {{chem2|TiCl4}} to give complexes containing amido ({{chem2|R2N−}}-containing) and imido ({{chem2|RN(2−)}}-containing) complexes. With ammonia, [[titanium nitride]] is formed. An illustrative reaction is the synthesis of [[tetrakis(dimethylamido)titanium]] {{chem2|Ti(N(CH3)2)4}}, a yellow, benzene-soluble liquid:<ref>{{cite journal|first1= D. C. |last1=Bradey |first2=M. |last2=Thomas|title= Some Dialkylamino-derivatives of Titanium and Zirconium|journal=[[J. Chem. Soc.]]| year=1960| pages=3857–3861| doi= 10.1039/JR9600003857}}</ref> This molecule is tetrahedral, with planar nitrogen centers.<ref>{{cite journal|author1=M. E. Davie |author2=T. Foerster |author3=S. Parsons |author4=C. Pulham |author5=D. W. H. Rankin |author6=B. A. Smart |title= The Crystal Structure of Tetrakis(dimethylamino)titanium(IV)|journal=[[Polyhedron (journal)|Polyhedron]]| year=2006| volume=25| pages=923–929|doi= 10.1016/j.poly.2005.10.019|issue= 4}}</ref>
:{{chem2|4 LiN(CH3)2 + TiCl4 → 4 LiCl + Ti(N(CH3)2)4}}

===Complexes with simple ligands===
{{chem2|TiCl4}} is a [[Lewis acid]] as implicated by its tendency to [[hydrolysis|hydrolyze]]. With the [[ether]] [[tetrahydrofuran|THF]], {{chem2|TiCl4}} reacts to give yellow crystals of {{chem2|TiCl4(THF)2}}. With chloride salts, {{chem2|TiCl4}} reacts to form sequentially {{chem2|[Ti2Cl9]−}}, {{chem2|[Ti2Cl10](2−)}} (see figure above), and {{chem2|[TiCl6](2−)}}.<ref>{{cite journal|first1= C. S.|last1= Creaser |first2=J. A. |last2=Creighton|title= Pentachloro- and Pentabromotitanate(IV) ions|journal= [[Dalton Transactions|Dalton Trans.]]| year=1975| pages= 1402–1405|doi= 10.1039/DT9750001402|issue= 14 }}</ref> The reaction of chloride ions with {{chem2|TiCl4}} depends on the counterion. {{chem2|[N(CH2CH2CH2CH3)4]Cl}} and {{chem2|TiCl4}} gives the pentacoordinate complex {{chem2|[N(CH2CH2CH2CH3)4][TiCl5]}}, whereas smaller {{chem2|[N(CH2CH3)4]+}} gives {{chem2|[N(CH2CH3)4]2[Ti2Cl10]}}. These reactions highlight the influence of electrostatics on the structures of compounds with highly ionic bonding.

===Redox===
Reduction of {{chem2|TiCl4}} with [[aluminium]] results in one-electron reduction. The trichloride ([[Titanium(III) chloride|{{chem2|TiCl3}}]]) and tetrachloride have contrasting properties: the trichloride is a colored solid, being a [[coordination polymer]], and is [[paramagnetic]]. When the reduction is conducted in [[Tetrahydrofuran|THF]] solution, the Ti(III) product converts to the light-blue adduct {{chem2|TiCl3(THF)3}}.

===Organometallic chemistry===
{{Main|Organotitanium compound}}
The [[organometallic chemistry]] of titanium typically starts from {{chem2|TiCl4}}. An important reaction involves sodium [[cyclopentadiene|cyclopentadienyl]] to give [[titanocene dichloride]], {{chem2|TiCl2(C5H5)2}}. This compound and many of its derivatives are precursors to [[Ziegler–Natta catalyst]]s. [[Tebbe's reagent]], useful in organic chemistry, is an aluminium-containing derivative of titanocene that arises from the reaction of titanocene dichloride with [[trimethylaluminium]]. It is used for the "olefination" reactions.<ref name="organoti" />

[[Arene]]s, such as {{chem2|C6(CH3)6}} react to give the [[sandwich complex|piano-stool complex]]es {{chem2|[Ti(C6R6)Cl3]+}} (R = H, {{chem2|CH3}}; see figure above). This reaction illustrates the high Lewis acidity of the {{chem2|TiCl3+}} entity, which is generated by abstraction of [[chloride]] from {{chem2|TiCl4}} by [[aluminium trichloride|{{chem2|AlCl3}}]].<ref name="TiCplx">{{cite journal|first1=F. |last1=Calderazzo |first2=I. |last2=Ferri |first3=G. |last3=Pampaloni |first4=S. |last4=Troyanov |title= ''η''<sup>6</sup>-Arene Derivatives of Titanium(IV), Zirconium(IV) and Hafnium(IV)|journal=J. Organomet. Chem.| year=1996| volume=518|issue=1–2 | pages=189–196|doi= 10.1016/0022-328X(96)06194-3}}</ref>

===Reagent in organic synthesis===
{{chem2|TiCl4}} finds occasional use in [[organic synthesis]], capitalizing on its [[Lewis acid]]ity, its [[oxophilic]]ity, and the electron-transfer properties of its reduced titanium halides. It is used in the [[Lewis acid catalysis|Lewis acid catalysed]] [[aldol addition]]<ref>Mariappan Periasamy (2002): "New synthetic methods using the TiCl4-NR3  reagent system", ''[[Arkivoc]]'', p. 151-166.</ref> Key to this application is the tendency of {{chem2|TiCl4}} to activate [[aldehyde]]s (RCHO) by formation of [[adduct]]s such as {{chem2|(RCHO)TiCl4OC(H)R}}.<ref>{{cite encyclopedia|first1= L.-L. |last1=Gundersen |first2=F. |last2=Rise |first3=K. |last3=Undheim |encyclopedia=Encyclopedia of Reagents for Organic Synthesis| publisher = J. Wiley & Sons|year=2004 |title=Titanium(IV) chloride |editor-first =L. |editor-last=Paquette |location=New York, NY |doi=10.1002/047084289X.rt119.pub2}}</ref>

==Toxicity and safety considerations==
Hazards posed by titanium tetrachloride generally arise from its reaction with water that releases [[hydrochloric acid]], which is severely corrosive itself and whose vapors are also extremely irritating. {{chem2|TiCl4}} is a strong [[Lewis acid]], which exothermically forms adducts with even weak bases such as [[THF]] and water.

==References==
{{reflist|30em}}

==General reading==
*{{cite book|last1=Holleman |first1=A. F. |last2=Wiberg |first2=E. |title=Inorganic Chemistry |publisher=Academic Press |location=San Diego, CA |date=2001 |isbn=978-0-12-352651-9}}
*{{Greenwood&Earnshaw}}

==External links==
*[http://www.epa.gov/ttn/atw/hlthef/titanium.html Titanium tetrachloride: Health Hazard Information]
*[http://webbook.nist.gov/chemistry/ NIST Standard Reference Database]
*[http://chemsub.online.fr/name/titanium_tetrachloride ChemSub Online: Titanium tetrachloride]

{{Titanium compounds}}
{{Chlorides}}

[[Category:Titanium(IV) compounds]]
[[Category:Chlorides]]
[[Category:Titanium halides]]
[[Category:Reagents for organic chemistry]]