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Titanium(III) chloride



Titanium(III) chloride
General
Other names titanium trichloride
titanous chloride
Molecular formula TiCl3
Molar mass 154.225 g/mol
Appearance red-violet crystals
CAS number [7705-07-9]
Properties
Density and phase 2.64  g/mL, solid
Solubility soluble in H2O
Stability deliquescent
Melting point 425°C (decomposes)
Thermodynamic data
Standard enthalpy
of formation
ΔfH°solid
-721.74 kJ/mol
Standard enthalpy
of formation
ΔfH°gas
-539.32 kJ/mol
Standard molar entropy
S°solid
139.74 J•K−1•mol−1
Standard molar entropy
S°gas
316.88 J•K−1•mol−1
Hazards
MSDS External MSDS
Main hazards corrosive
NFPA 704
RTECS number XR1924000
Related compounds
Other anions Titanium(III) fluoride
Titanium(III) bromide
Titanium(III) iodide
Other cations Scandium(III) chloride
Chromium(III) chloride
Related compounds Vanadium(III) chloride
Titanium(IV) chloride
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references

Titanium(III) chloride is the chemical compound with the formula TiCl3. This deceptively simple name describes several distinct species as well as a hydrated salt. TiCl3 is one of the most common halides of titanium and is an important catalyst for the manufacture of polyolefins.

Additional recommended knowledge

Contents

Electronic properties

In TiCl3, each Ti atom has one d electron, rendering most of its forms paramagnetic, i.e. the substance is attracted into a magnetic field. The paramagnetism of TiCl3's contrasts with the diamagnetism (the property of being repelled from a magnetic field) of the trihalides of hafnium and zirconium. These heavier metals engage in metal-metal bonding, but the Ti(III) ion does not typically.

Solutions of titanium(III) chloride have violet coloration which arises from excitations of its d-electron. The colour is not very intense since the transition is forbidden.

Structure

Solid TiCl3 can be obtained in one of four forms or polymorphs. These forms can be distinguished by crystallography as well as studies on their magnetic properties which probes exchange interactions.[1]

Beta form

β-TiCl3 crystallizes as brown needle. The structure of this material features chains of TiCl6 octahedra that share opposite faces such that the closest Ti-Ti is 2.91 Å. This short distance allows strong metal-metal bonding.

"Violet layered" forms

The three violet layered" forms, named for their color and its 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.

Ternary alkali halides

Caesium chloride treated with titanium(II) chloride and hexachlorobenzene produces crystalline CsTi2Cl7. The product contains 1:2 molar mixtures of CsCl and TiCl3. CsCl3 and Cl4 stack alternatively in an ABAC sequence with Ti3+ in one quarter of the octahedral holes.[2]

Synthesis and selected handling properties

Titanium(IV) chloride can be reduced to TiCl3; this conversion is generally accomplished electrochemically. It is sold as a mixture with aluminium trichloride. This mixture can be separated to afford TiCl3(THF)3.[3]

Ti3+ is prepared in situ as part of the method of analyzing titanium-containing samples such as ores. Thus, acidic solutions of Ti4+ are reduced using Jones reductor with amalgamated zinc.[4] The resulting Ti3+ containing product is analyzed by redox titration.

TiCl3 and most of its complexes are handled under an inert atmosphere to prevent reactions with oxygen. Slow deterioration occurs in air-exposed titanium trichloride, often results in erratic results, e.g. in reductive coupling reactions[5].

Applications in Ziegler-Natta catalyst

TiCl3 is a useful Ziegler-Natta catalyst, although the catalytic activities vary with the method of preparation.[6]

Other reactions of Ti(III) chloride

TiCl3 forms a variety of coordination complexes, most of which are octahedral. The light-blue crystalline adduct TiCl3(THF)3 forms when TiCl3 is refluxed with tetrahydrofuran.[7]

TiCl3 + 3C4H8O → TiCl3(OC4H8)3

A dark green charge-neutral complex arises from complexation with dimethylamine:

TiCl3 + 3Me2NH → TiCl3(NHMe2)3 + CH3Cl

TiCl3 reacts with acetylacetone to form a tris acetylacetonate complex.

TiCl3 + 3NH4(acac) → Ti(acac)3 + 3NH4Cl

The product is used as cross-linking agent for cellulose films used in polyethylene catalysts. Ti(acac)3 air-oxidizes to give orange TiO(acac)2, which is ineffective in cross-linking.[8]

Above 200 °C, TiCl3 undergoes ammonolysis.6

The ternary halides, such as A3TiCl6, have structures that depend on the cation (A) added.[9]

References

  1. ^ Starr, C.; Bitter, F.; Kaufman, A.R.Lippard, S. "Halides & Halide Complexes" in (1968) Progress in Inorganic Chemistry, Cotton (Ed.) Volume 9, (John Wiley & Sons, Inc.) pp. 6
  2. ^ Holm, R. H. "Stabilized Low Oxidation States" in (1971) Progress in Inorganic Chemistry, Lippard, S. J. (Ed.) Volume 14, (John Wiley & Sons, Inc.) pp. 17
  3. ^ Jongen, L. and Meyer, G. (2004). "Caesium heptaiododititanate(III), CsTi2I7". Zeitschrift für Anorganische und Allgemeine Chemie 630: 211-212. DOI
  4. ^ Kisova, L.; Sotkova, S.; Konemdova, I. (1994). "Electrode Kinetics of the Ti(IV)/Ti(III) System in Water and in Water Dimethylformamide and Water Dimethyl Sulfoxide Mixed Solvents". Collection of Czechoslovak Chemical Communications 59: 1279-1286. DOI
  5. ^ Fleming, M. P; McMurry, J. E. (1981). "Reductive Coupling of Carbonys to Alkenes: Adamantylideneadamantane". Organic Syntheses 60: 113. PDF
  6. ^ Ueno, H.; Imanishi, K.; Ueki, S.; Kohara, T. (2000). "Kinetics Study of Propene Polymerization with Porous Titanium Trichloride". Chemical Society of Japan 7: 495. Abstract
  7. ^ 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: 755 - 757. DOI: 10.1021/om060486d..
  8. ^ Manzer, L. E., "Tetrahydrofuran Complexes of Selected Early Transition Metals", in (1982) Inorganic Syntheses, Flacker, J. P. (Ed.) Volume 21, pp. 137
  9. ^ Cor, M.; Lewis, J.; Nyholm, R. S., S. "Titanium" in (1966) Progress in Inorganic Chemistry, Lippard, S. J. (Ed.) Volume 7, (John Wiley & Sons, Inc.) pp. 391
  10. ^ Fowles, G. W. A. "Reacting Halides with Liquid Ammonia" in (1965) Progress in Inorganic Chemistry, Lippard, S. J. (Ed.) Volume 6, (John Wiley & Sons, Inc.) pp. 2
  11. ^ Hinz, D.; Gloger, T. and Meyer, G. (2000). "Ternary halides of the type A3MX6. Part 9. Crystal structures of Na3TiCl6 and K3TiCl6". Zeitschrift für Anorganische und Allgemeine Chemie 626: 822-824. Abstract


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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Titanium(III)_chloride". A list of authors is available in Wikipedia.
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