Chromium(III) chloride (also called chromic chloride) is a violet coloured solid with the formula CrCl₃.

Although it is ionic, the the solid state structure is kinetically inert so that anhydrous CrCl₃ is surprisingly reluctant to dissolve in water. However, in the presence of a trace of a reducing agent capable of reducing Cr³⁺ to Cr²⁺, the CrCl₃ dissolves rapidly to form soluble complexes containing hydrated Cr³⁺ ions. The common commercial form of the hydrate is the dark green complex shown in the picture, [CrCl₂(H₂O)₄]Cl.2H₂O, but two other forms are known, viz., pale green [CrCl(H₂O)₅]Cl₂.H₂O and violet [Cr(H₂O)₆]Cl₃. From ancient Greece (Ionic) An Ionian is a member of one of the four great divisions of the ancient Greek people. ... The most fundamental reactions in chemistry are the redox processes. ...

This inertness means that CrCl₃ is generally sluggish to react without the presence of a reducing agent. When it does react it undergoes ligand substitution reactions to form other complexes of chromium(III). It reacts as a Lewis acid, forming stable chloro complexes such as [CrCl₆]^3-. In chemistry, a ligand is an atom, ion or functional group that is bonded to one or more central atoms or ions, usually metals generally through co-ordinate covalent bond. ... In chemistry, a Lewis acid is any acid that can accept a pair of electrons and form a coordinate covalent bond, after the American chemist Gilbert Lewis. ...

Chemical properties

Chromium(III) chloride is a Lewis acid, classified as "hard" according to the Hard-Soft Acid-Base theory. However it is also a chloro complex which is quite inert to substitution, so in fact it is ordinarily quite unreactive. The low reactivity of the d³ Cr³⁺ ion can be explained using crystal field theory. One way of opening CrCl₃ up to substitution in solution is to reduce even a trace amount to CrCl₂, for example using zinc in hydrochloric acid. This chromium(II) compound undergoes substitution easily, and it can exchange electrons with CrCl₃ via a chloride bridge, allowing all of the CrCl₃ to react quickly. In chemistry, a Lewis acid is any acid that can accept a pair of electrons and form a coordinate covalent bond, after the American chemist Gilbert Lewis. ... The HSAB concept, also known as HSAB theory, is widely used in chemistry for explaining stability of compounds, reaction paths etc. ... A complex in chemistry and biochemistry is a reversible association of molecules, atoms, or ions through weak non-covalent chemical bonds. ... Crystal field theory is used to describe the electronic structure of transition metal complexes. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... The chemical substance hydrochloric acid is the aqueous (water-based) solution of hydrogen chloride (HCl) gas. ... The chloride ion is formed when the element chlorine picks up one electron to form the anion (negatively charged ion) Cl−. The salts of hydrochloric acid HCl contain chloride ions and are also called chlorides. ...

The commonest form of CrCl₃ sold commercially is a dark green hexahydrate with the structure [CrCl₂(H₂O)₄]Cl.2H₂O, and like the anhydrous form it is also very inert towards substitution.

If substitution reactions are performed in the presence of a trace of Cr²⁺, then CrCl₃ can undergo substitution with ligands such as water (giving violet [Cr(H₂O)₆]³⁺) or pyridine: Pyridine is a clear liquid with an odor that is sour, putrid, and fish-like. ...

CrCl₃ + 3 C₅H₅N → [CrCl₃(C₅H₅N)₃] Pyridine is a clear liquid with an odor that is sour, putrid, and fish-like. ...

Such complexes are usually octahedral.

With molten alkali metal chlorides such as potassium chloride, CrCl₃ gives octahedral complexes of the type K₃CrCl₆, as well as K₃Cr₂Cl₉ which is also octahedral but where the two chromiums are linked via three chloride bridges. The alkali metals are the series of elements in Group 1 (IUPAC style) of the periodic table, excluding hydrogen: that is, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). ... The chloride ion is formed when the element chlorine picks up one electron to form the negatively charged ion Cl−. The salts of hydrochloric acid HCl are also called chlorides. ... The chemical compound potassium chloride (KCl) is a metal halide composed of potassium and chlorine. ...

Preparation

Anhydrous chromium(III) chloride may be prepared from chromium metal and chlorine directly, or indirectly using chromium(III) oxide with carbon and chlorine at 800 °C^[4]: General Name, Symbol, Number chromium, Cr, 24 Chemical series transition metals Group, Period, Block 6, 4, d Appearance silvery metallic Atomic mass 51. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Atomic mass 35. ... Chromium(III) oxide, also known as chromium sesquioxide or chromia, is one of four oxides of chromium, chemical formula Cr2O3. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Atomic mass 35. ...

Cr₂O₃(s) + 3 C(s) + 3 Cl₂(g) → 2 CrCl₃(s) + 3 CO(g) Chromium(III) oxide, also known as chromium sesquioxide or chromia, is one of four oxides of chromium, chemical formula Cr2O3. ... A solid is a phase of matter, characterized by resistance to deformation and changes of volume. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... A solid is a phase of matter, characterized by resistance to deformation and changes of volume. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Atomic mass 35. ... A gas is one of the phases of matter. ... A solid is a phase of matter, characterized by resistance to deformation and changes of volume. ... Carbon monoxide, chemical formula CO, is a colourless, odourless, flammable and highly toxic gas. ... A gas is one of the phases of matter. ...

It may also be prepared from the hexahydrate, by heating with thionyl chloride which reacts with the water of hydration. Thionyl chloride (or thionyl dichloride) is an inorganic compound with the formula S O Cl2. ...

The hydrated chloride may be made by dissolving the metal in hydrochloric acid. The chloride ion is formed when the element chlorine picks up one electron to form the anion (negatively charged ion) Cl−. The salts of hydrochloric acid HCl contain chloride ions and are also called chlorides. ... The chemical substance hydrochloric acid is the aqueous (water-based) solution of hydrogen chloride (HCl) gas. ...

Uses

Chromium(III) chloride is used as the source of chromium for many inorganic compounds of chromium, for example dibenzenechromium(0), an analogue of ferrocene: An inorganic compound is a chemical compound not containing carbon and hydrogen atoms bonded to each other. ... Ferrocene Fe(C5H5)2 is the prototypical metallocene, a type of organometallic chemical compound, consisting of two cyclopentadienyl rings bound on opposite sides of a central iron atom and forming an organometallic sandwich compound. ...

Download high resolution version (1059x289, 5 KB)Preparation of dibenzenechromium(0) from CrCl3 This image has been released into the public domain by its creator and original copyright holder. ...

A significant use of CrCl₃ in organic synthesis is for the in situ preparation of chromium(II) chloride, a popular reagent for (A) reduction of alkyl halides and for (B) the synthesis of (E)-alkenyl halides. The reaction is usually performed using two moles of CrCl₃ per mole of lithium aluminium hydride, although if aqueous acidic conditions are appropriate zinc and hydrochloric acid may be sufficient. Organic synthesis is the construction of organic molecules via chemical processes. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ... The mole (symbol: mol) is one of the seven SI base units and is commonly used in chemistry. ... Lithium Aluminium Hydride (LiAlH4), commonly abbreviated to LAH, is a powerful reducing agent used in organic chemistry. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... The chemical substance hydrochloric acid is the aqueous (water-based) solution of hydrogen chloride (HCl) gas. ...

Download high resolution version (1256x241, 5 KB)Chemical reactions of CrCl3 involving CrCl2 as an intermediate This image has been released into the public domain by its creator and original copyright holder. ...

Precautions

Although trivalent chromium is far less poisonous than hexavalent, chromium salts are generally considered highly toxic. Avoid ingestion and inhalation of dust. Wear gloves and goggles. In chemistry, valency is the power of an atom of an element to combine with other atoms measured by the number of electrons which an atom will give, take, or share to form a chemical bond. ...

Suppliers/Manufacturers

• Alfa
• Sigma-Aldrich
• Strem
• Fisher
• VWR

Template: inorganic_stylesheet1 Overview History Chemical properties Preparation Uses Biological role Precautions Suppliers/Manufacturers References Template: Inorganic_stylesheet1 ...

References

1. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
2. Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
3. The Merck Index, 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960.
4. D. Nicholls, Complexes and First-Row Transition Elements, Macmillan Press, London, 1973.
5. A. F. Wells, 'Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
6. J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.
7. K. Takai, in Handbook of Reagents for Organic Synthesis, Volume 1: Reagents, Auxiliaries and Catalysts for C-C Bond Formation, (R. M. Coates, S. E. Denmark, eds.), pp. 206-211, Wiley, New York, 1999.

External links

• International Chemical Safety Card 1316 (anhydr. CrCl₃)
• International Chemical Safety Card 1532 (CrCl₃·6H₂O)
• NIOSH Pocket Guide to Chemical Hazards
• IARC Monograph "Chromium and Chromium compounds"