Titanium(III) chloride
Titanium chloride is the inorganic compound
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula TiCl3. At least four distinct species have this formula; additionally hydrated
Water of crystallization
In crystallography, water of crystallization or water of hydration or crystallization water is water that occurs in crystals. Water of crystallization is necessary for the maintenance of crystalline properties, but capable of being removed by sufficient heat...

 derivatives are known. TiCl3 is one of the most common halides of titanium and is an important catalyst for the manufacture of polyolefin
A polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry...


Electronic properties

In TiCl3, each Ti atom has one d electron, rendering its derivatives paramagnetic, i.e. the substance is attracted into a magnetic field. The paramagnetism contrasts with the diamagnetism
Diamagnetism is the property of an object which causes it to create a magnetic field in opposition to an externally applied magnetic field, thus causing a repulsive effect. Specifically, an external magnetic field alters the orbital velocity of electrons around their nuclei, thus changing the...

 (the property of being repelled from a magnetic field) of the trihalides of hafnium and zirconium: in these heavier metals engage in metal-metal bonding.

Solutions of titanium(III) chloride are violet, which arises from excitations
Ligand field theory
Ligand field theory describes the bonding, orbital arrangement, and other characteristics of coordination complexes. It represents an application of molecular orbital theory to transition metal complexes. A transition metal ion has nine valence atomic orbitals, five d, one s, and three p orbitals...

 of its d-electron. The colour is not very intense since the transition is forbidden
Selection rule
In physics and chemistry a selection rule, or transition rule, formally constrains the possible transitions of a system from one state to another. Selection rules have been derived for electronic, vibrational, and rotational transitions...

 by the Laporte selection rule.


Four solid forms or polymorphs
Polymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...

 of TiCl3 are known. All feature titanium in an octahedral coordination sphere. These forms can be distinguished by crystallography
Crystallography is the experimental science of the arrangement of atoms in solids. The word "crystallography" derives from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and grapho = write.Before the development of...

 as well as by their magnetic properties, which probes exchange interaction
Exchange interaction
In physics, the exchange interaction is a quantum mechanical effect without classical analog which increases or decreases the expectation value of the energy or distance between two or more identical particles when their wave functions overlap...

s. 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 geometry, close-packing of equal spheres is a dense arrangement of congruent spheres in an infinite, regular arrangement . Carl Friedrich Gauss proved that the highest average density – that is, the greatest fraction of space occupied by spheres – that can be achieved by a regular lattice...

. In γ-TiCl3, the chlorides anions are cubic close-packed
Cubic crystal system
In crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals....

. 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, direct Zr-Zr bonding is indicated in zirconium(III) chloride
Zirconium(III) chloride
Zirconium chloride is a the inorganic compound with formula ZrCl3. It is a blue-black solid that is highly sensitive to air.-Preparation:...

. The difference between the Zr(III) and Ti(III) materials is attributed in part to the relative radii of these metal centers.

Synthesis and reactivity

Titanium(IV) chloride can be reduced to TiCl3. It is sold as a mixture with aluminium trichloride. This mixture can be separated to afford TiCl3(THF
Follicular B helper T cells , are antigen-experienced CD4+ T cells found in the B cell follicles of secondary lymphoid organs such as lymph nodes, spleens and Peyer's patches, and are identified by their constitutive expression of the B cell follicle homing receptor CXCR5...

)3. TiCl3 and most of its complexes are handled under an air-free conditions to prevent reactions with oxygen. Slow deterioration occurs in air-exposed titanium trichloride, often results in erratic results, e.g. in reductive coupling reaction
Coupling reaction
A coupling reaction in organic chemistry is a catch-all term for a variety of reactions where two hydrocarbon fragments are coupled with the aid of a metal catalyst...


It can be syntetised by disolving titanium in aqueus hydrochloric acid.
2 Ti + 6 HCl → 2 TiCl3 + 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
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...

TiCl3 + 3 C4H8O → TiCl3(OC4H8)3

An analogous dark green complex arises from complexation with dimethylamine
Dimethylamine is an organic compound with the formula 2NH. This secondary amine is a colorless, flammable liquified gas with an ammonia-like odor. Dimethylamine is generally encountered as a solution in water at concentrations up to around 40%...

. In a reaction where all ligands are exchanged, TiCl3 is a precursor to the tris acetylacetonate
Acetylacetone is an organic compound that famously exists in two tautomeric forms that rapidly interconvert. The less stable tautomer is a diketone formally named pentane-2,4-dione. The more common tautomer is the enol form. The pair of tautomers rapidly interconvert and are treated as a single...


The more reduced titanium(II) chloride
Titanium(II) chloride
Titanium chloride is the chemical compound with the formula TiCl2. The black solid has been studied only moderately, probably because of its high reactivity. Ti is a strong reducing agent: it has a high affinity for oxygen and reacts irreversibly with water to produce H2. The usual preparation is...

 is prepared by the thermal disproportionation
Disproportionation, also known as dismutation is used to describe a specific type of redox reaction in which a species is simultaneously reduced and oxidized so as to form two different products....

 of TiCl3 at 500 °C. The equilibrium is driven by the loss of volatile TiCl4
Titanium tetrachloride
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 an unusual example of a metal halide that is highly volatile...

2 TiCl3 → TiCl2 + TiCl4

The ternary halides, such as A3TiCl6, have structures that depend on the cation (A+) added. Caesium chloride
Caesium chloride
Caesium chloride is the inorganic compound with the formula CsCl. This colorless solid is an important source of caesium ions in a variety of applications. Its crystal structure forms a major structural type where each caesium ion is coordinated by 8 chlorine ions...

 treated with titanium(II) chloride and hexachlorobenzene
Hexachlorobenzene, or perchlorobenzene, is a chlorocarbon with the molecular formula C6Cl6. It is a fungicide formerly used as a seed treatment, especially on wheat to control the fungal disease bunt...

 produces crystalline CsTi2Cl7. In these structures Ti3+ exhibits octahedral coordination geometry.


TiCl3 is the main Ziegler-Natta catalyst
Ziegler-Natta catalyst
A Ziegler–Natta catalyst is a catalyst used in the synthesis of polymers of 1-alkenes . Three types of Ziegler–Natta catalysts are currently employed:* Solid and supported catalysts based on titanium compounds...

, responsible for the formation of most industrial production of polypropylene
Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...

. The catalytic activities depend strongly on the polymorph and the method of preparation.

Laboratory use

TiCl3 is also a reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...

 in organic synthesis, useful for reductive coupling reactions, often in the presence of added reducing agents such as zinc. It reduces oxime
An oxime is a chemical compound belonging to the imines, with the general formula R1R2C=NOH, where R1 is an organic side chain and R2 may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted oximes form a closely related family of compounds...

s to imine
An imine is a functional group or chemical compound containing a carbon–nitrogen double bond, with the nitrogen attached to a hydrogen atom or an organic group. If this group is not a hydrogen atom, then the compound is known as a Schiff base...

s. Titanium trichloride can reduce nitrate to ammonium ion thereby allowing for the sequential analysis of nitrate and ammonia.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.