Titanium tetrachloride

Last updated
Titanium tetrachloride
Titanium-tetrachloride-3D-vdW.png
Sample of Titanium tetrachloride 01.jpg
Names
IUPAC name
Titanium(IV) chloride
Other names
Titanium tetrachloride
Tetrachlorotitanium
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.028.584 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-441-9
MeSH Titanium+tetrachloride
PubChem CID
RTECS number
  • XR1925000
UNII
UN number 1838
  • InChI=1S/4ClH.Ti/h4*1H;/q;;;;+4/p-4 Yes check.svgY
    Key: XJDNKRIXUMDJCW-UHFFFAOYSA-J Yes check.svgY
  • InChI=1/4ClH.Ti/h4*1H;/q;;;;+4/p-4/rCl4Ti/c1-5(2,3)4
    Key: XJDNKRIXUMDJCW-FOGBWSKZAG
  • Cl[Ti](Cl)(Cl)Cl
Properties
TiCl4
Molar mass 189.679 g/mol
AppearanceColourless liquid
Odor penetrating acid odor
Density 1.726 g/cm3
Melting point −24.1 °C (−11.4 °F; 249.1 K)
Boiling point 136.4 °C (277.5 °F; 409.5 K)
reacts (exothermic hydrolysis) [1]
Solubility soluble in dichloromethane, [2] toluene, [3] pentane [4]
Vapor pressure 1.3 kPa (20 °C)
−54.0·10−6 cm3/mol
1.61 (10.5 °C)
Viscosity 827 μPa s
Structure
Tetragonal
Tetrahedral
0 D
Thermochemistry
Std molar
entropy (S⦵298)
355 J·mol−1·K−1 [5]
−763 kJ·mol−1 [5]
Hazards [6]
Occupational safety and health (OHS/OSH):
Main hazards
Toxic, corrosive, reacts with water to release HCl
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-skull.svg GHS-pictogram-exclam.svg
Danger
H314, H317, H330, H335, H370, H372
P280, P301+P330+P331, P304+P340, P305+P351+P338, P308+P310
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
3
0
2
W
Safety data sheet (SDS) MSDS
Related compounds
Other anions
Titanium(IV) bromide
Titanium(IV) fluoride
Titanium(IV) iodide
Other cations
Hafnium(IV) chloride
Zirconium(IV) chloride
Related compounds
 Titanium(II) chloride
Titanium(III) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)
Crystals of frozen titanium tetrachloride melting into the liquid Titanium tetrachloride phases.jpg
Crystals of frozen titanium tetrachloride melting into the liquid

Titanium tetrachloride is the inorganic compound with the formula TiCl4. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl4 is a volatile liquid. Upon contact with humid air, it forms thick clouds of titanium dioxide (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 (TiCl4). [7] [8]

Contents

Properties and structure

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, VCl4 being another example. This property reflects the fact that molecules of TiCl4 weakly self-associate. Most metal chlorides are polymers, wherein the chloride atoms bridge between the metals. Its melting point is similar to that of CCl4. [9] [10]

Ti4+ has a "closed" electronic shell, with the same number of electrons as the noble gas argon. The tetrahedral structure for TiCl4 is consistent with its description as a d0 metal center (Ti4+) surrounded by four identical ligands. This configuration leads to highly symmetrical structures, hence the tetrahedral shape of the molecule. TiCl4 adopts similar structures to TiBr4 and TiI4; the three compounds share many similarities. TiCl4 and TiBr4 react to give mixed halides TiCl4−xBrx, where x = 0, 1, 2, 3, 4. Magnetic resonance measurements also indicate that halide exchange is also rapid between TiCl4 and VCl4. [11]

TiCl4 is soluble in toluene and chlorocarbons. Certain arenes form complexes of the type [(C6R6)TiCl3]+. [12] TiCl4 reacts exothermically with donor solvents such as THF to give hexacoordinated adducts. [13] Bulkier ligands (L) give pentacoordinated adducts TiCl4L.

Production

TiCl4 is produced by the chloride process, which involves the reduction of titanium oxide ores, typically ilmenite (FeTiO3), with carbon under flowing chlorine at 900 °C. Impurities are removed by distillation. [10]

2 FeTiO3 + 7 Cl2 + 6 C → 2 TiCl4 + 2 FeCl3 + 6 CO

The coproduction of 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 TiO2, is derived from ilmenite by removal of iron, either using carbon reduction or extraction with sulfuric acid. Crude TiCl4 contains a variety of other volatile halides, including vanadyl chloride (VOCl3), silicon tetrachloride (SiCl4), and tin tetrachloride (SnCl4), which must be separated. [10]

Applications

Production of titanium metal

The world's supply of titanium metal, about 250,000 tons per year, is made from TiCl4. The conversion involves the reduction of the tetrachloride with magnesium metal. This procedure is known as the Kroll process: [14]

2 Mg + TiCl4 → 2 MgCl2 + Ti

In the Hunter process, liquid sodium is the reducing agent instead of magnesium. [15]

Production of titanium dioxide

Around 90% of the TiCl4 production is used to make the pigment titanium dioxide (TiO2). The conversion involves hydrolysis of TiCl4, a process that forms hydrogen chloride: [14]

TiCl4 + 2 H2O → TiO2 + 4 HCl

In some cases, TiCl4 is oxidised directly with oxygen:

TiCl4 + O2 → TiO2 + 2 Cl2

Smoke screens

It has been used to produce smoke screens 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 hydrated HCl's effects on the respiratory system. [16]

Chemical reactions

Titanium tetrachloride is a versatile reagent that forms diverse derivatives including those illustrated below. [17]

TiCl4cmpds.png

A characteristic reaction of TiCl4 is its easy hydrolysis, signaled by the release of HCl vapors and titanium oxides and oxychlorides. Titanium tetrachloride has been used to create naval smokescreens, as the hydrochloric acid aerosol and titanium dioxide that is formed scatter light very efficiently. This smoke is corrosive, however. [10]

Alcohols react with TiCl4 to give alkoxides with the formula [Ti(OR)4]n (R = alkyl, n = 1, 2, 4). As indicated by their formula, these alkoxides 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: [18]

TiCl4 + 2 Hacac → Ti(acac)2Cl2 + 2 HCl

Organic amines react with TiCl4 to give complexes containing amido (R2N−-containing) and imido (RN2−-containing) complexes. With ammonia, titanium nitride is formed. An illustrative reaction is the synthesis of tetrakis(dimethylamido)titanium Ti(N(CH3)2)4, a yellow, benzene-soluble liquid: [19] This molecule is tetrahedral, with planar nitrogen centers. [20]

4 LiN(CH3)2 + TiCl4 → 4 LiCl + Ti(N(CH3)2)4

Complexes with simple ligands

TiCl4 is a Lewis acid as implicated by its tendency to hydrolyze. With the ether THF, TiCl4 reacts to give yellow crystals of TiCl4(THF)2. With chloride salts, TiCl4 reacts to form sequentially [Ti2Cl9]−, [Ti2Cl10]2− (see figure above), and [TiCl6]2−. [21] The reaction of chloride ions with TiCl4 depends on the counterion. [N(CH2CH2CH2CH3)4]Cl and TiCl4 gives the pentacoordinate complex [N(CH2CH2CH2CH3)4][TiCl5], whereas smaller [N(CH2CH3)4]+ gives [N(CH2CH3)4]2[Ti2Cl10]. These reactions highlight the influence of electrostatics on the structures of compounds with highly ionic bonding.

Redox

Reduction of TiCl4 with aluminium results in one-electron reduction. The trichloride (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 THF solution, the Ti(III) product converts to the light-blue adduct TiCl3(THF)3.

Organometallic chemistry

The organometallic chemistry of titanium typically starts from TiCl4. An important reaction involves sodium cyclopentadienyl to give titanocene dichloride, TiCl2(C5H5)2. This compound and many of its derivatives are precursors to Ziegler–Natta catalysts. 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. [17]

Arenes, such as C6(CH3)6 react to give the piano-stool complexes [Ti(C6R6)Cl3]+ (R = H, CH3; see figure above). This reaction illustrates the high Lewis acidity of the TiCl+3 entity, which is generated by abstraction of chloride from TiCl4 by AlCl3. [12]

Reagent in organic synthesis

TiCl4 finds occasional use in organic synthesis, capitalizing on its Lewis acidity, its oxophilicity, and the electron-transfer properties of its reduced titanium halides. It is used in the Lewis acid catalysed aldol addition [22] Key to this application is the tendency of TiCl4 to activate aldehydes (RCHO) by formation of adducts such as (RCHO)TiCl4OC(H)R. [23]

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. TiCl4 is a strong Lewis acid, which exothermically forms adducts with even weak bases such as THF and water.

Related Research Articles

A Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, is a catalyst used in the synthesis of polymers of 1-alkenes (alpha-olefins). Two broad classes of Ziegler–Natta catalysts are employed, distinguished by their solubility:

Iron(III) chloride describes the inorganic compounds with the formula FeCl3(H2O)x. Also called ferric chloride, these compounds are some of the most important and commonplace compounds of iron. They are available both in anhydrous and in hydrated forms which are both hygroscopic. They feature iron in its +3 oxidation state. The anhydrous derivative is a Lewis acid, while all forms are mild oxidizing agents. It is used as a water cleaner and as an etchant for metals.

In inorganic chemistry, chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. Each such chemical has at least one silicon-chlorine bond. Trichlorosilane is produced on the largest scale. The parent chlorosilane is silicon tetrachloride.

<span class="mw-page-title-main">Hafnium tetrachloride</span> Chemical compound

Hafnium(IV) chloride is the inorganic compound with the formula HfCl4. This colourless solid is the precursor to most hafnium organometallic compounds. It has a variety of highly specialized applications, mainly in materials science and as a catalyst.

Boron trichloride is the inorganic compound with the formula BCl3. This colorless gas is a reagent in organic synthesis. It is highly reactive towards water.

<span class="mw-page-title-main">Vanadium oxytrichloride</span> Chemical compound

Vanadium oxytrichloride is the inorganic compound with the formula VOCl3. This yellow distillable liquid hydrolyzes readily in air. It is an oxidizing agent. It is used as a reagent in organic synthesis. Samples often appear red or orange owing to an impurity of vanadium tetrachloride.

<span class="mw-page-title-main">Titanocene dichloride</span> Chemical compound

Titanocene dichloride is the organotitanium compound with the formula (η5-C5H5)2TiCl2, commonly abbreviated as Cp2TiCl2. This metallocene is a common reagent in organometallic and organic synthesis. It exists as a bright red solid that slowly hydrolyzes in air. It shows antitumour activity and was the first non-platinum complex to undergo clinical trials as a chemotherapy drug.

<span class="mw-page-title-main">Zirconium(IV) chloride</span> Chemical compound

Zirconium(IV) chloride, also known as zirconium tetrachloride, is an inorganic compound frequently used as a precursor to other compounds of zirconium. This white high-melting solid hydrolyzes rapidly in humid air.

Titanium(III) chloride is the inorganic compound with the formula TiCl3. At least four distinct species have this formula; additionally hydrated derivatives are known. TiCl3 is one of the most common halides of titanium and is an important catalyst for the manufacture of polyolefins.

Vanadium tetrachloride is the inorganic compound with the formula VCl4. This reddish-brown liquid serves as a useful reagent for the preparation of other vanadium compounds.

<span class="mw-page-title-main">Titanium(II) chloride</span> Chemical compound

Titanium(II) chloride is the chemical compound with the formula TiCl2. The black solid has been studied only moderately, probably because of its high reactivity. Ti(II) is a strong reducing agent: it has a high affinity for oxygen and reacts irreversibly with water to produce H2. The usual preparation is the thermal disproportionation of TiCl3 at 500 °C. The reaction is driven by the loss of volatile TiCl4:

<span class="mw-page-title-main">Platinum(IV) chloride</span> Chemical compound

Platinum(IV) chloride is the inorganic compound of platinum and chlorine with the empirical formula PtCl4. This brown solid features platinum in the 4+ oxidation state.

<span class="mw-page-title-main">Titanium tetrabromide</span> Chemical compound

Titanium tetrabromide is the chemical compound with the formula TiBr4. It is the most volatile transition metal bromide. The properties of TiBr4 are an average of TiCl4 and TiI4. Some key properties of these four-coordinated Ti(IV) species are their high Lewis acidity and their high solubility in nonpolar organic solvents. TiBr4 is diamagnetic, reflecting the d0 configuration of the metal centre.

<span class="mw-page-title-main">Organotitanium chemistry</span>

Organotitanium chemistry is the science of organotitanium compounds describing their physical properties, synthesis, and reactions. Organotitanium compounds in organometallic chemistry contain carbon-titanium chemical bonds. They are reagents in organic chemistry and are involved in major industrial processes.

The chloride process is used to separate titanium from its ores. The goal of the process is to win high purity titanium dioxide from ores such as ilmenite (FeTiO3) and rutile (TiO2). The strategy exploits the volatility of TiCl4, which is readily purified and converted to the dioxide. Millions of tons of TiO2 are produced annually by this process, mainly for use as white pigments. The chloride process has largely displaced the older sulfate process, which relies on hot sulfuric acid to extract iron and other impurities from ores.

Organotellurium chemistry describes the synthesis and properties of organotellurium compounds, chemical compounds containing a carbon-tellurium chemical bond. Organotellurium chemistry is a lightly studied area, in part because of it having few applications.

<span class="mw-page-title-main">Niobium(IV) chloride</span> Chemical compound

Niobium(IV) chloride, also known as niobium tetrachloride, is the chemical compound of formula NbCl4. This compound exists as dark violet crystals, is highly sensitive to air and moisture, and disproportiates into niobium(III) chloride and niobium(V) chloride when heated.

<span class="mw-page-title-main">Metal halides</span>

Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, such as palladium chloride.

<span class="mw-page-title-main">(Cyclopentadienyl)titanium trichloride</span> Chemical compound

(Cyclopentadienyl)titanium trichloride is an organotitanium compound with the formula (C5H5)TiCl3. It is a moisture sensitive orange solid. The compound adopts a piano stool geometry.

The +4 oxidation state dominates titanium chemistry, but compounds in the +3 oxidation state are also numerous. Commonly, titanium adopts an octahedral coordination geometry in its complexes, but tetrahedral TiCl4 is a notable exception. Because of its high oxidation state, titanium(IV) compounds exhibit a high degree of covalent bonding.

References

  1. ↑ Eremenko, B. V.; Bezuglaya, T. N.; Savitskaya, A. N.; Malysheva, M. L.; Kozlov, I. S.; Bogodist, L. G. (2001). "Stability of Aqueous Dispersions of the Hydrated Titanium Dioxide Prepared by Titanium Tetrachloride Hydrolysis". Colloid Journal. 63 (2): 173–178. doi:10.1023/A:1016673605744. S2CID   93971747.
  2. ↑ "titanium(IV) chloride, 1M soln. in dichloromethane". Alfa Aesar. Retrieved 7 March 2018.
  3. ↑ "Titanium(IV) chloride solution 1.0 M in toluene". Sigma-Aldrich. Retrieved 7 March 2018.
  4. ↑ Butts, Edward H De. "patent US3021349A".
  5. 1 2 Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). Houghton-Mifflin. p. A23. ISBN   978-0-618-94690-7.
  6. ↑ "Classifications - CL Inventory". echa.europa.eu.
  7. ↑ Archived 2013-02-17 at the Wayback Machine American Chemistry Council – "Titanium Tetrachloride: Stepping Stone to Amazing Technology"
  8. ↑ "Archived copy". Archived from the original on 2014-03-19. Retrieved 2013-04-10.{{cite web}}: CS1 maint: archived copy as title (link) Iowa State University – "Chemistry Material Safety Data Sheets"
  9. ↑ Earnshaw, A.; Greenwood, N. (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann.
  10. 1 2 3 4 Heinz Sibum; Volker Güther; Oskar Roidl; Fathi Habashi; Hans Uwe Wolf; Carsten Siemers (2017). "Titanium, Titanium Alloys, and Titanium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. pp. 1–35. doi:10.1002/14356007.a27_095.pub2. ISBN   978-3-527-30673-2.
  11. ↑ Webb, S. P.; Gordon, M. S. (1999). "Intermolecular Self-Interactions of the Titanium Tetrahalides TiX4 (X = F, Cl, Br)". J. Am. Chem. Soc. 121 (11): 2552–2560. doi:10.1021/ja983339i.
  12. 1 2 Calderazzo, F.; Ferri, I.; Pampaloni, G.; Troyanov, S. (1996). "η6-Arene Derivatives of Titanium(IV), Zirconium(IV) and Hafnium(IV)". J. Organomet. Chem. 518 (1–2): 189–196. doi:10.1016/0022-328X(96)06194-3.
  13. ↑ Manzer, L. E. (1982). "31. Tetragtdrfuran Complexes of Selected Early Transition Metals". Inorganic Syntheses. Vol. 21. pp. 135–40. doi:10.1002/9780470132524.ch31. ISBN   978-0-470-13252-4.
  14. 1 2 Völz, Hans G.; et al. (2006). "Pigments, Inorganic". Inorganic Pigments. Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.n20_n04. ISBN   978-3-527-30673-2.
  15. ↑ Schaschke, Carl (2014). "Hunter process". A Dictionary of Chemical Engineering . Oxford University Press. doi:10.1093/acref/9780199651450.001.0001. ISBN   978-0-19-965145-0.
  16. ↑ The Royal Navy at War (DVD). London: Imperial War Museum. 2005.
  17. 1 2 "Organotitanium Reagents in Organic Synthesis (Reactivity and Structure Concepts in Organic Chemistry, Vol 24)" Manfred T. Reetz 1986 ISBN   0-387-15784-0
  18. ↑ Wilkie, C. A.; Lin, G.; Haworth, D. T. (1979). "Cis -[Dihalobis(2,4-Pentaedionato)Titanium(IV)] Complexes". Inorganic Syntheses. Vol. 19. pp. 145–148. doi:10.1002/9780470132500.ch33. ISBN   978-0-470-13250-0.{{cite book}}: |journal= ignored (help)
  19. ↑ Bradey, D. C.; Thomas, M. (1960). "Some Dialkylamino-derivatives of Titanium and Zirconium". J. Chem. Soc. : 3857–3861. doi:10.1039/JR9600003857.
  20. ↑ M. E. Davie; T. Foerster; S. Parsons; C. Pulham; D. W. H. Rankin; B. A. Smart (2006). "The Crystal Structure of Tetrakis(dimethylamino)titanium(IV)". Polyhedron . 25 (4): 923–929. doi:10.1016/j.poly.2005.10.019.
  21. ↑ Creaser, C. S.; Creighton, J. A. (1975). "Pentachloro- and Pentabromotitanate(IV) ions". Dalton Trans. (14): 1402–1405. doi:10.1039/DT9750001402.
  22. ↑ Mariappan Periasamy (2002): "New synthetic methods using the TiCl4-NR3 reagent system", Arkivoc , p. 151-166.
  23. ↑ Gundersen, L.-L.; Rise, F.; Undheim, K. (2004). "Titanium(IV) chloride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York, NY: J. Wiley & Sons.

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