Titanium(III) chloride

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Titanium(III) chloride
Beta-TiCl3-chain-from-xtal-3D-balls.png
Beta-TiCl3-chains-packing-from-xtal-3D-balls-B.png
β-TiCl3 viewed along the chains
TiCl3.jpg
TiCl3 solution
Names
Other names
titanium trichloride
titanous chloride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.845
EC Number
  • 231-728-9
PubChem CID
RTECS number
  • XR1924000
UNII
Properties
TiCl3
Molar mass 154.225 g/mol
Appearancered-violet crystals
hygroscopic
Density 2.64 g/cm3
Melting point 425 °C (797 °F; 698 K)(decomposes)
Boiling point 960 °C (1,760 °F; 1,230 K)
very soluble
Solubility soluble in acetone, acetonitrile, certain amines;
insoluble in ether and hydrocarbons
+1110.0·10−6 cm3/mol
1.4856
Hazards
Main hazards Corrosive
Safety data sheet External MSDS
Related compounds
Other anions
Titanium(III) fluoride
Titanium(III) bromide
Titanium(III) iodide
Other cations
Scandium(III) chloride
Chromium(III) chloride
Vanadium(III) chloride
Related compounds
Titanium(IV) chloride
Titanium(II) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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.

Contents

Structure and bonding

In TiCl3, each Ti atom has one d electron, rendering its derivatives paramagnetic, i.e. the substance is attracted into a magnetic field. Solutions of titanium(III) chloride are violet, which arises from excitations of its d-electron. The colour is not very intense since the transition is forbidden by the Laporte selection rule.

Four solid forms or polymorphs of TiCl3 are known. All feature titanium in an octahedral coordination sphere. These forms can be distinguished by crystallography as well as by their magnetic properties, which probes exchange interactions. β-TiCl3 crystallizes as brown needles. Its structure consists of chains of TiCl6 octahedra that share opposite faces such that the closest Ti—Ti contact is 2.91 Å. This short distance indicates strong metal-metal interactions (See Figure in upper right). The three violet "layered" forms, named for their color and their tendency to flake, are called alpha, gamma, and delta. In α-TiCl3, the chloride anions are hexagonal close-packed. In γ-TiCl3, the chlorides anions are cubic close-packed. Finally, disorder in shift successions, causes an intermediate between alpha and gamma structures, called the delta (δ) form. The TiCl6 share edges in each form, with 3.60 Å being the shortest distance between the titanium cations. This large distance between titanium cations precludes direct metal-metal bonding. In contrast, the trihalides of the heavier metals hafnium and zirconium engage in metal-metal bonding. Direct Zr-Zr bonding is indicated in zirconium(III) chloride. The difference between the Zr(III) and Ti(III) materials is attributed in part to the relative radii of these metal centers. [1]

Synthesis and reactivity

TiCl3 is produced usually by reduction of titanium(IV) chloride. Older reduction methods used hydrogen: [2]

2 TiCl4 + H2 → 2 HCl + 2 TiCl3

It is conveniently reduced with aluminium and sold as a mixture with aluminium trichloride, TiCl3·AlCl3. This mixture can be separated to afford TiCl3(THF)3. [3] The complex adopts a meridional structure. [4]

Its hydrate can be synthesised by dissolving titanium in aqueous hydrochloric acid.

2 Ti + 6 HCl + 6 H2O → 2 TiCl3(H2O)3 + 3 H2

TiCl3 forms a variety of coordination complexes, most of which are octahedral. The light-blue crystalline adduct TiCl3(THF)3 forms when TiCl3 is treated with tetrahydrofuran. [5]

TiCl3 + 3 C4H8O → TiCl3(OC4H8)3

An analogous dark green complex arises from complexation with dimethylamine. In a reaction where all ligands are exchanged, TiCl3 is a precursor to the tris acetylacetonate complex.

The more reduced titanium(II) chloride is prepared by the thermal disproportionation of TiCl3 at 500 °C. The reaction is driven by the loss of volatile TiCl4: [6]

2 TiCl3 → TiCl2 + TiCl4

The ternary halides, such as A3TiCl6, have structures that depend on the cation (A+) added. [7] Caesium chloride treated with titanium(II) chloride and hexachlorobenzene produces crystalline CsTi2Cl7. In these structures Ti3+ exhibits octahedral coordination geometry. [8]

Applications

TiCl3 is the main Ziegler–Natta catalyst, responsible for most industrial production of polyethylene. The catalytic activities depend strongly on the polymorph of the TiCl3 (α vs. β vs. γ vs. δ) and the method of preparation. [9]

Laboratory use

TiCl3 is also a specialized reagent in organic synthesis, useful for reductive coupling reactions, often in the presence of added reducing agents such as zinc. It reduces oximes to imines. [10] Titanium trichloride can reduce nitrate to ammonium ion thereby allowing for the sequential analysis of nitrate and ammonia. [11] Slow deterioration occurs in air-exposed titanium trichloride, often resulting in erratic results, e.g. in reductive coupling reactions. [12]

Safety

TiCl3 and most of its complexes are typically handled under air-free conditions to prevent reactions with oxygen and moisture. Depending on the method for its preparation, samples of TiCl3 can be relatively air stable or pyrophoric. [13] [14]

Related Research Articles

Titanium tetrachloride inorganic chemical compound

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 spectacular opaque clouds of titanium dioxide (TiO2) and hydrated hydrogen chloride. It is sometimes referred to as "tickle" or "tickle 4" due to the phonetic resemblance of its molecular formula (TiCl4) to the word.

Europium(III) chloride chemical compound

Europium(III) chloride is an inorganic compound with the formula EuCl3. The anhydrous compound is a yellow solid. Being hygroscopic it rapidly absorbs water to form a white crystalline hexahydrate, EuCl3·6H2O, which is colourless. The compound is used in research.

Aluminium chloride chemical compound

Aluminium chloride (AlCl3), also known as aluminium trichloride, is the main compound of aluminium and chlorine. It is white, but samples are often contaminated with iron(III) chloride, giving it a yellow color. The solid has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, but large amounts are also used in other areas of the chemical industry. The compound is often cited as a Lewis acid. It is an example of an inorganic compound that reversibly changes from a polymer to a monomer at mild temperature.

Chromium(III) chloride chemical compound

Chromium(III) chloride (also called chromic chloride) describes any of several compounds of with the formula CrCl3 • xH2O, where x can be 0, 5, and 6. The anhydrous compound with the formula CrCl3 is a violet solid. The most common form of the trichloride is the dark green hexahydrate, CrCl3 • 6H2O. Chromium chlorides find use as catalysts and as precursors to dyes for wool.

Iron(II) chloride chemical compound

Iron(II) chloride, also known as ferrous chloride, is the chemical compound of formula FeCl2. It is a paramagnetic solid with a high melting point. The compound is white, but typical samples are often off-white. FeCl2 crystallizes from water as the greenish tetrahydrate, which is the form that is most commonly encountered in commerce and the laboratory. There is also a dihydrate. The compound is highly soluble in water, giving pale green solutions.

Scandium chloride chemical compound

Scandium(III) chloride is the inorganic compound with the formula ScCl3. It is a white, high-melting ionic compound, which is deliquescent and highly water-soluble. Scandium(III) chloride is mainly of interest in the research laboratory. Both the anhydrous form and hexahydrate (ScCl3•6H2O) are commercially available.

Hafnium tetrachloride 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.

McMurry reaction

The McMurry reaction is an organic reaction in which two ketone or aldehyde groups are coupled to form an alkene using a titanium chloride compound such as titanium(III) chloride and a reducing agent. The reaction is named after its co-discoverer, John E. McMurry. The McMurry reaction originally involved the use of a mixture TiCl3 and LiAlH4, which produces the active reagent(s). Related species have been developed involving the combination of TiCl3 or TiCl4 with various other reducing agents, including potassium, zinc, and magnesium. This reaction is related to the Pinacol coupling reaction which also proceeds by reductive coupling of carbonyl compounds.

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

Titanocene dichloride 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.

Zirconium(IV) chloride chemical compound

Zirconium(IV) chloride, also known as zirconium tetrachloride, (ZrCl4) is an inorganic compound frequently used as a precursor to other compounds of zirconium. This white high-melting solid hydrolyzes rapidly in humid air.

Vanadium(III) chloride chemical compound

Vanadium trichloride is the inorganic compound with the formula VCl3. This purple salt is a common precursor to other vanadium(III) complexes.

Indium(III) chloride chemical compound

Indium(III) chloride is the chemical compound with the formula InCl3. This salt is a white, flaky solid with applications in organic synthesis as a Lewis acid. It is also the most available soluble derivative of indium.

Titanium(II) chloride 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:

Zirconium(III) chloride chemical compound

Zirconium(III) chloride is an inorganic compound with formula ZrCl3. It is a blue-black solid that is highly sensitive to air.

Metal halides class of chemical compounds

Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. Covalently bonded metal halides may be discrete molecules, such as uranium hexafluoride, or they may form polymeric structures, such as palladium chloride.

Molybdenum(III) chloride is the inorganic compound with the formula MoCl3.

Bis(dinitrogen)bis(1,2-bis(diphenylphosphino)ethane)molybdenum(0) chemical compound

trans-Bis(dinitrogen)bis[1,2-bis(diphenylphosphino)ethane]molybdenum(0) is a coordination complex with the formula Mo(N2)2(dppe)2. It is a relatively air stable yellow-orange solid. It is notable as being the first dinitrogen containing complex of molybdenum.

Bis(cyclopentadienyl)titanium(III) chloride

Bis(cyclopentadienyl)titanium(III) chloride, also known as the Nugent–RajanBabu reagent, is the organotitanium compound which exists as a dimer with the formula [(C5H5)2TiCl]2. It is an air sensitive green solid. The complex finds specialized use in synthetic organic chemistry as a single electron reductant.

Niobium(III) chloride also known as niobium trichloride is a compound of niobium and chlorine. It is a non-stoichiometric compound, with formula NbClx for 2.667 ≤ x ≤ 3.13.

References

  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  2. Sherfey, J. M. (2007). "Titanium(III) Chloride and Titanium(III) Bromide". Inorganic Syntheses. 6: 57–61. doi:10.1002/9780470132371.ch17. ISBN   9780470132371.
  3. Jones, N. A.; Liddle, S. T.; Wilson, C.; Arnold, P. L. (2007). "Titanium(III) Alkoxy-N-heterocyclic Carbenes and a Safe, Low-Cost Route to TiCl3(THF)3". Organometallics. 26 (3): 755–757. doi:10.1021/om060486d.
  4. Handlovic, M.; Miklos, D.; Zikmund, M. "The structure of trichlorotris(tetrahydrofuran)titanium(III)" Acta Crystallographica 1981, volume B37(4), 811-14.doi : 10.1107/S056774088100438X
  5. Manzer, L. E.; Deaton, Joe; Sharp, Paul; Schrock, R. R. (1982). "Tetrahydrofuran Complexes of Selected Early Transition Metals". Inorg. Synth. 21: 137. doi:10.1002/9780470132524.ch31.
  6. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN   0-12-352651-5.
  7. Hinz, D.; Gloger, T. & Meyer, G. (2000). "Ternary halides of the type A3MX6. Part 9. Crystal structures of Na3TiCl6 and K3TiCl6". Zeitschrift für Anorganische und Allgemeine Chemie. 626 (4): 822–824. doi:10.1002/(SICI)1521-3749(200004)626:4<822::AID-ZAAC822>3.0.CO;2-6.
  8. Jongen, L. & Meyer, G. (2004). "Caesium heptaiododititanate(III), CsTi2I7". Zeitschrift für Anorganische und Allgemeine Chemie. 630 (2): 211–212. doi:10.1002/zaac.200300315.
  9. Kenneth S. Whiteley,T. Geoffrey Heggs, Hartmut Koch, Ralph L. Mawer, Wolfgang Immel, "Polyolefins" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. doi : 10.1002/14356007.a21_487
  10. Lise-Lotte Gundersen, Frode Rise, Kjell Undheim, José Méndez-Andino, "Titanium(III) Chloride" in Encyclopedia of Reagents for Organic Synthesis doi : 10.1002/047084289X.rt120.pub2
  11. "Determining Ammonium & Nitrate ions using a Gas Sensing Ammonia Electrode". Soil and Crop Science Society of Florida, Vol. 65, 2006, D.W.Rich, B.Grigg, G.H.Snyder
  12. Fleming, Michael P; McMurry, John E. "Reductive Coupling of Carbonyls to Alkenes: Adamantylideneadamantane". Organic Syntheses .; Collective Volume, 7, p. 1
  13. Ingraham, T. R.; Downes, K. W.; Marier, P. (1957). "The Production OF Titanium Trichloride By Arc-Induced Hydrogen Reduction Of Titanium Tetrachloride". Canadian Journal of Chemistry. 35 (8): 850–872. doi:10.1139/v57-118. ISSN   0008-4042.
  14. Pohanish, Richard P. & Greene, Stanley A. (2009). Wiley Guide to Chemical Incompatibilities (3 ed.). John Wiley & Sons. p. 1010. ISBN   9780470523308.