Iron(II) chloride

Last updated
Iron(II) chloride
Iron(II) chloride anhydrate.jpg
Anhydrous
Ferrous chloride tetrahydrate.jpg
Tetrahydrate
Iron(II)-chloride-xtal-sheet-3D-balls-A.png
Structure of anhydrous ferrous chloride (  Fe,   Cl)
Trans-FeCl2(H2O)4.png
structure of tetrahydrate
Names
IUPAC names
Iron(II) chloride
Iron dichloride
Other names
Ferrous chloride
Rokühnite
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.028.949 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-843-4
PubChem CID
RTECS number
  • NO5400000
UNII
  • InChI=1S/2ClH.Fe/h2*1H;/q;;+2/p-2 Yes check.svgY
    Key: NMCUIPGRVMDVDB-UHFFFAOYSA-L Yes check.svgY
  • InChI=1/2ClH.Fe/h2*1H;/q;;+2/p-2
    Key: NMCUIPGRVMDVDB-NUQVWONBAL
  • anhydrous:Cl[Fe]Cl
  • tetrahydrate:Cl[Fe-4](Cl)([OH2+])([OH2+])([OH2+])[OH2+]
Properties
FeCl2
Molar mass 126.751 g/mol (anhydrous)
198.8102 g/mol (tetrahydrate)
AppearanceTan solid (anhydrous)
Pale green solid (di-tetrahydrate)
Density 3.16 g/cm3 (anhydrous)
2.39 g/cm3 (dihydrate)
1.93 g/cm3 (tetrahydrate)
Melting point 677 °C (1,251 °F; 950 K) (anhydrous)
120 °C (dihydrate)
105 °C (tetrahydrate)
Boiling point 1,023 °C (1,873 °F; 1,296 K) (anhydrous)
64.4 g/100 mL (10 °C),
68.5 g/100 mL (20 °C),
105.7 g/100 mL (100 °C)
Solubility in THF Soluble
log P −0.15
+14750·10−6 cm3/mol
Structure
Monoclinic
Octahedral at Fe
Pharmacology
B03AA05 ( WHO )
Hazards
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 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
0
0
NIOSH (US health exposure limits):
REL (Recommended)
TWA 1 mg/m3 [1]
Safety data sheet (SDS) Iron (II) chloride MSDS
Related compounds
Other anions
Iron(II) fluoride
Iron(II) bromide
Iron(II) iodide
Other cations
Cobalt(II) chloride
Manganese(II) chloride
Copper(II) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

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.

Contents

Production

Structure of "FeCl2(thf)x", Fe4Cl8(thf)6, illustrating both tetrahedral and octahedral coordination geometries. CIZFEW01.png
Structure of "FeCl2(thf)x", Fe4Cl8(thf)6, illustrating both tetrahedral and octahedral coordination geometries.

Hydrated forms of ferrous chloride are generated by treatment of wastes from steel production with hydrochloric acid. Such solutions are designated "spent acid," or "pickle liquor" especially when the hydrochloric acid is not completely consumed:

Fe + 2 HCl → FeCl2 + H2

The production of ferric chloride involves the use of ferrous chloride. Ferrous chloride is also a byproduct from the production of titanium, since some titanium ores contain iron. [3]

Anhydrous FeCl2

Ferrous chloride is prepared by addition of iron powder to a solution of hydrochloric acid in methanol. This reaction gives the methanol solvate of the dichloride, which upon heating in a vacuum at about 160 °C converts to anhydrous FeCl2. [4] The net reaction is shown:

Fe + 2 HCl → FeCl2 + H2

FeBr2 and FeI2 can be prepared analogously.

An alternative synthesis of anhydrous ferrous chloride is the reduction of FeCl3 with chlorobenzene: [5]

2 FeCl3 + C6H5Cl → 2 FeCl2 + C6H4Cl2 + HCl

For the preparation of ferrocene ferrous chloride is generated in situ by comproportionation of FeCl3 with iron powder in tetrahydrofuran (THF). [6] Ferric chloride decomposes to ferrous chloride at high temperatures.

Hydrates

The dihydrate, FeCl2(H2O)2, crystallizes from concentrated hydrochloric acid. [7] The dihydrate is a coordination polymer. Each Fe center is coordinated to four doubly bridging chloride ligands. The octahedron is completed by a pair of mutually trans aquo ligands. [8]

Subunit of FeCl2(H2O)2 lattice. MX2(H2O)2.png
Subunit of FeCl2(H2O)2 lattice.

Reactions

Tetra(pyridine)iron dichloride is prepared by treating ferrous chloride with pyridine. FeCl2py4.png
Tetra(pyridine)iron dichloride is prepared by treating ferrous chloride with pyridine.

FeCl2 and its hydrates form complexes with many ligands. For example, solutions of the hydrates react with two molar equivalents of [(C2H5)4N]Cl to give the salt [(C2H5)4N]2[FeCl4]. [10]

The anhydrous FeCl2, which is soluble in THF, [2] is a standard precursor in organometallic synthesis. FeCl2 is used to generate NHC complexes in situ for cross coupling reactions. [11]

Applications

Unlike the related ferrous sulfate and ferric chloride, ferrous chloride has few commercial applications. Aside from use in the laboratory synthesis of iron complexes, ferrous chloride serves as a coagulation and flocculation agent in wastewater treatment, especially for wastes containing chromate or sulfides. [12] It is used for odor control in wastewater treatment. It is used as a precursor to make various grades of hematite that can be used in a variety of pigments. It is the precursor to hydrated iron(III) oxides that are magnetic pigments. [3] FeCl2 finds some use as a reagent in organic synthesis. [13]

Natural occurrence

Lawrencite, (Fe,Ni)Cl2, is the natural counterpart, and a typically (though rarely occurring) meteoritic mineral. [14] The natural form of the dihydrate is rokühnite - a very rare mineral. [15] Related, but more complex (in particular, basic or hydrated) minerals are hibbingite, droninoite and kuliginite.

Related Research Articles

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.

<span class="mw-page-title-main">Zinc chloride</span> Chemical compound

Zinc chloride is an inorganic chemical compound with the formula ZnCl2·nH2O, with n ranging from 0 to 4.5, forming hydrates. Zinc chloride, anhydrous and its hydrates, are colorless or white crystalline solids, and are highly soluble in water. Five hydrates of zinc chloride are known, as well as four forms of anhydrous zinc chloride. All forms of zinc chloride are deliquescent. Zinc chloride finds wide application in textile processing, metallurgical fluxes, and chemical synthesis. In a major monograph, zinc chlorides have been described as "one of the important compounds of zinc."

<span class="mw-page-title-main">Titanium tetrachloride</span> 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 thick clouds of titanium dioxide 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.

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

Samarium(III) chloride, also known as samarium trichloride, is an inorganic compound of samarium and chloride. It is a pale yellow salt that rapidly absorbs water to form a hexahydrate, SmCl3.6H2O. The compound has few practical applications but is used in laboratories for research on new compounds of samarium.

<span class="mw-page-title-main">Europium(III) chloride</span> 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.

<span class="mw-page-title-main">Aluminium chloride</span> Chemical compound

Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula AlCl3. It forms a hexahydrate with the formula [Al(H2O)6]Cl3, containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are colourless crystals, but samples are often contaminated with iron(III) chloride, giving them a yellow colour.

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

Manganese(II) chloride is the dichloride salt of manganese, MnCl2. This inorganic chemical exists in the anhydrous form, as well as the dihydrate (MnCl2·2H2O) and tetrahydrate (MnCl2·4H2O), with the tetrahydrate being the most common form. Like many Mn(II) species, these salts are pink, with the paleness of the color being characteristic of transition metal complexes with high spin d5 configurations.

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

Cobalt(II) chloride is an inorganic compound, a salt of cobalt and chlorine, with the formula CoCl
2
. The compound forms several hydrates CoCl
2
·nH
2
O
, for n = 1, 2, 6, and 9. Claims of the formation of tri- and tetrahydrates have not been confirmed. The anhydrous form is a blue crystalline solid; the dihydrate is purple and the hexahydrate is pink. Commercial samples are usually the hexahydrate, which is one of the most commonly used cobalt salts in the lab.

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

Copper(II) chloride, also known as cupric chloride, is an inorganic compound with the chemical formula CuCl2. The monoclinic yellowish-brown anhydrous form slowly absorbs moisture to form the orthorhombic blue-green dihydrate CuCl2·2H2O, with two water molecules of hydration. It is industrially produced for use as a co-catalyst in the Wacker process.

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

Chromium(III) chloride (also called chromic chloride) is an inorganic chemical compound with the chemical formula CrCl3. It forms several hydrates with the formula CrCl3·nH2O, among which are hydrates where n can be 5 (chromium(III) chloride pentahydrate CrCl3·5H2O) or 6 (chromium(III) chloride hexahydrate CrCl3·6H2O). The anhydrous compound with the formula CrCl3 are violet crystals, while the most common form of the chromium(III) chloride are the dark green crystals of hexahydrate, CrCl3·6H2O. Chromium chlorides find use as catalysts and as precursors to dyes for wool.

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

Nickel(II) chloride (or just nickel chloride) is the chemical compound NiCl2. The anhydrous salt is yellow, but the more familiar hydrate NiCl2·6H2O is green. Nickel(II) chloride, in various forms, is the most important source of nickel for chemical synthesis. The nickel chlorides are deliquescent, absorbing moisture from the air to form a solution. Nickel salts have been shown to be carcinogenic to the lungs and nasal passages in cases of long-term inhalation exposure.

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

Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)n, where n varies from 0 to 3. These are diamagnetic solids featuring octahedral Rh(III) centres. Depending on the value of n, the material is either a dense brown solid or a soluble reddish salt. The soluble trihydrated (n = 3) salt is widely used to prepare compounds used in homogeneous catalysis, notably for the industrial production of acetic acid and hydroformylation.

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

Tin(II) chloride, also known as stannous chloride, is a white crystalline solid with the formula SnCl2. It forms a stable dihydrate, but aqueous solutions tend to undergo hydrolysis, particularly if hot. SnCl2 is widely used as a reducing agent (in acid solution), and in electrolytic baths for tin-plating. Tin(II) chloride should not be confused with the other chloride of tin; tin(IV) chloride or stannic chloride (SnCl4).

<span class="mw-page-title-main">Trimethylsilyl chloride</span> Organosilicon compound with the formula (CH3)3SiCl

Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound, with the formula (CH3)3SiCl, often abbreviated Me3SiCl or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. It is widely used in organic chemistry.

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

Chromium(II) chloride describes inorganic compounds with the formula CrCl2(H2O)n. The anhydrous solid is white when pure, however commercial samples are often grey or green; it is hygroscopic and readily dissolves in water to give bright blue air-sensitive solutions of the tetrahydrate Cr(H2O)4Cl2. Chromium(II) chloride has no commercial uses but is used on a laboratory-scale for the synthesis of other chromium complexes.

<span class="mw-page-title-main">Uranyl chloride</span> Chemical compound

Uranyl chloride refers to inorganic compounds with the formula UO2Cl2(H2O)n where n = 0, 1, or 3. These are yellow-colored salts.

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.

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

Vanadium(III) chloride describes the inorganic compound with the formula VCl3 and its hydrates. It forms a purple anhydrous form and a green hexahydrate [VCl2(H2O)4]Cl·2H2O. These hygroscopic salts are common precursors to other vanadium(III) complexes and is used as a mild reducing agent.

<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.

Lanthanide trichlorides are a family of inorganic compound with the formula LnCl3, where Ln stands for a lanthanide metal. The trichlorides are standard reagents in applied and academic chemistry of the lanthanides. They exist as anhydrous solids and as hydrates.

References

  1. NIOSH Pocket Guide to Chemical Hazards. "#0346". National Institute for Occupational Safety and Health (NIOSH).
  2. 1 2 Cotton, F. A.; Luck, R. L.; Son, K.-A. (1991). "New polynuclear compounds of iron(II) chloride with oxygen donor ligands Part I. Fe4Cl8(THF)6: synthesis and a single crystal X-ray structure determination". Inorganica Chimica Acta. 179: 11–15. doi:10.1016/S0020-1693(00)85366-9.
  3. 1 2 Egon Wildermuth, Hans Stark, Gabriele Friedrich, Franz Ludwig Ebenhöch, Brigitte Kühborth, Jack Silver, Rafael Rituper "Iron Compounds" in Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Wienheim, 2005.
  4. G. Winter; Thompson, D. W.; Loehe, J. R. (1973). "Iron(II) Halides". Inorganic Syntheses. Vol. 14. pp. 99–104. doi:10.1002/9780470132456.ch20. ISBN   978-0-470-13245-6.{{cite book}}: |journal= ignored (help)
  5. P. Kovacic and N. O. Brace (1960). "Iron(II) Chloride". Inorganic Syntheses. Vol. 6. pp. 172–173. doi:10.1002/9780470132371.ch54. ISBN   978-0-470-13237-1.{{cite book}}: |journal= ignored (help)
  6. Wilkinson, G. (1956). "Ferrocene". Organic Syntheses . 36: 31. doi:10.15227/orgsyn.036.0031 .
  7. K. H.. Gayer; L. Woontner (1957). "Iron(II) Chloride 2-Hydrate". Inorganic Syntheses. Vol. 5. pp. 179–181. doi:10.1002/9780470132364.ch48. ISBN   978-0-470-13236-4.{{cite book}}: |journal= ignored (help)
  8. Morosin, B.; Graeber, E. J. (1965). "Crystal structures of manganese(II) and iron(II) chloride dihydrate". Journal of Chemical Physics. 42 (3): 898–901. Bibcode:1965JChPh..42..898M. doi:10.1063/1.1696078.
  9. Baudisch, Oskar; Hartung, Walter H. (1939). "Tetrapyridino-Ferrous Chloride (Yellow Salt)". Inorganic Syntheses. Vol. 1. pp. 184–185. doi:10.1002/9780470132326.ch64. ISBN   978-0-470-13232-6.
  10. N. S. Gill, F. B. Taylor (1967). "Tetrahalo Complexes of Dipositive Metals in the First Transition Series". Inorganic Syntheses. Vol. 9. pp. 136–142. doi:10.1002/9780470132401.ch37. ISBN   978-0-470-13240-1.{{cite book}}: |journal= ignored (help)
  11. Bi-Jie Li; Xi-Sha Zhang; Zhang-Jie Shi (2014). "Cross-Coupling of Alkenyl/Aryl Carboxylates with Grignard Reagents via Fe-Catalyzed C-O Bond Activation". Org. Synth. 91: 83–92. doi: 10.15227/orgsyn.091.0083 .
  12. Jameel, Pervez (1989). "The Use of Ferrous Chloride to Control Dissolved Sulfides in Interceptor Sewers". Journal (Water Pollution Control Federation). 61 (2): 230–236. JSTOR   25046917.
  13. Andrew D. White; David G. Hilmey (2009). "Iron(II) Chloride". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.ri055.pub2. ISBN   978-0-471-93623-7.
  14. "Lawrencite".
  15. "Rokühnite".

See also