:Iron(II) chloride

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| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 443880274

| Name = Iron(II) chloride

| ImageFileL1 = Iron(II) chloride anhydrate.jpg

| ImageCaptionL1 = Anhydrous

| ImageFileR1 = Eisen(II)-chlorid-Tetrahydrat.jpg

| ImageCaptionR1 = Tetrahydrate

| ImageFileL2 = Iron(II)-chloride-xtal-sheet-3D-balls-A.png

| ImageCaptionL2 = Structure of anhydrous ferrous chloride ({{colorbox|purple}} Fe, {{colorbox|green}} Cl)

| ImageFileR2 = Trans-FeCl2(H2O)4.png

| ImageCaptionR2 = structure of tetrahydrate

| IUPACName = Iron(II) chloride
Iron dichloride

| OtherNames = Ferrous chloride
Rokühnite

| Section1 = {{Chembox Identifiers

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 22866

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = S3Y25PHP1W

| InChI = 1/2ClH.Fe/h2*1H;/q;;+2/p-2

| InChIKey = NMCUIPGRVMDVDB-NUQVWONBAL

| ChEBI_Ref = {{ebicite|correct|EBI}}

| ChEBI = 30812

| SMILES = Cl[Fe]Cl

| SMILES_Comment = anhydrous

| SMILES1 = Cl[Fe-4](Cl)([OH2+])([OH2+])([OH2+])[OH2+]

| SMILES1_Comment = tetrahydrate

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/2ClH.Fe/h2*1H;/q;;+2/p-2

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = NMCUIPGRVMDVDB-UHFFFAOYSA-L

| CASNo = 7758-94-3

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo2_Ref = {{cascite|changed|??}}

| CASNo2 = 16399-77-2

| CASNo2_Comment = (dihydrate)

| CASNo3_Ref = {{cascite|changed|??}}

| CASNo3 = 13478-10-9

| CASNo3_Comment = (tetrahydrate)

| PubChem = 24458

| RTECS = NO5400000

| EINECS = 231-843-4}}

| Section2 = {{Chembox Properties

| Formula = FeCl₂

| MolarMass = 126.751{{nbsp}}g/mol (anhydrous)
198.8102{{nbsp}}g/mol (tetrahydrate)

| Appearance = Tan solid (anhydrous)
Pale green solid (di-tetrahydrate)

| Density = 3.16{{nbsp}}g/cm³ (anhydrous)
2.39{{nbsp}}g/cm³ (dihydrate)
1.93{{nbsp}}g/cm³ (tetrahydrate)

| Solvent1 = THF

| Solubility1 = Soluble

| Solubility = 64.4{{nbsp}}g/100{{nbsp}}mL (10 °C),
68.5{{nbsp}}g/100{{nbsp}}mL (20 °C),
105.7{{nbsp}}g/100{{nbsp}}mL (100 °C)

| MeltingPtC = 677

| MeltingPt_notes = (anhydrous)
120 °C (dihydrate)
105 °C (tetrahydrate)

| BoilingPtC = 1023

| BoilingPt_notes = (anhydrous)

| LogP = −0.15

| MagSus = +{{val|14750}}·10⁻⁶{{nbsp}}cm³/mol}}

| Section3 = {{Chembox Structure

| Coordination = Octahedral at Fe

| CrystalStruct = Monoclinic}}

| Section6 = {{Chembox Pharmacology

| ATCCode_prefix = B03

| ATCCode_suffix = AA05}}

| Section7 = {{Chembox Hazards

| ExternalSDS = [https://www.fishersci.com/shop/msdsproxy?productName=I90500&productDescription=FERROUS+CHLORIDE+CERTIED+500G&catNo=I90-500&vendorId=VN00033897&storeId=10652 Iron (II) chloride MSDS]

| FlashPt =

| GHSPictograms = {{GHS05}}{{GHS07}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|290|302|315|317|318|412}}

| PPhrases = {{P-phrases|P234|P261|P264|P264+P265|P270|P272|P273|P280|P301+P317|P302+P352|P305+P354+P338|P317|P321|P330|P332+P317|P333+P317|P362+P364|P390|P406|P501}}

| MainHazards =

| NFPA-H = 3

| NFPA-F = 0

| NFPA-R = 0

| NFPA-S =

| REL = TWA 1{{nbsp}}mg/m³{{PGCH|0346}}}}

| Section8 = {{Chembox Related

| OtherAnions = Iron(II) fluoride
Iron(II) bromide
Iron(II) iodide

| OtherCations = Cobalt(II) chloride
Manganese(II) chloride
Copper(II) chloride}}

}}

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.

Production

File:CIZFEW01.png

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.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.

Anhydrous FeCl<sub>2</sub>

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.{{cite book | author = G. Winter | journal = Inorg. Synth. | year = 1973 | volume = 14 | pages = 99–104 | doi = 10.1002/9780470132456.ch20 | last2 = Thompson | first2 = D. W. | last3 = Loehe | first3 = J. R.| title = Inorganic Syntheses | chapter = Iron(II) Halides | isbn = 978-0-470-13245-6 }} 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:{{cite book | author = P. Kovacic and N. O. Brace | title = Inorganic Syntheses | journal = Inorg. Synth. | year = 1960 | volume = 6 | pages = 172–173 | doi = 10.1002/9780470132371.ch54 | chapter = Iron(II) Chloride| isbn = 978-0-470-13237-1 }}

: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).{{OrgSynth|title = Ferrocene|authorlink = Geoffrey Wilkinson|last = Wilkinson|first = G.|volume = 36|page = 31|year = 1956|doi = 10.15227/orgsyn.036.0031}} Ferric chloride decomposes to ferrous chloride at high temperatures.

Hydrates

The dihydrate, FeCl₂(H₂O)₂, crystallizes from concentrated hydrochloric acid.{{cite book | author1 = K. H.. Gayer| author2 = L. Woontner | title = Inorganic Syntheses | chapter = Iron(II) Chloride 2-Hydrate | journal = Inorg. Synth. | year = 1957 | volume = 5 | pages = 179–181 | doi = 10.1002/9780470132364.ch48 | isbn = 978-0-470-13236-4 }} 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.{{cite journal|title=Crystal structures of manganese(II) and iron(II) chloride dihydrate|author1=Morosin, B.|author2=Graeber, E. J.|journal=Journal of Chemical Physics|year=1965|volume=42|issue=3|pages=898–901|doi=10.1063/1.1696078|bibcode=1965JChPh..42..898M}}

File:MX2(H2O)2.png

Reactions

file:FeCl2py4.png is prepared by treating ferrous chloride with pyridine.{{cite book |doi=10.1002/9780470132326.ch64|chapter=Tetrapyridino-Ferrous Chloride (Yellow Salt)|year=1939|last1=Baudisch|first1=Oskar|last2=Hartung|first2=Walter H.|title=Inorganic Syntheses|pages=184–185|volume=1|isbn=978-0-470-13232-6}}]]

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].{{cite book | author = N. S. Gill, F. B. Taylor | title = Inorganic Syntheses | journal = Inorg. Synth. | year = 1967 | volume = 9 | pages = 136–142 | doi = 10.1002/9780470132401.ch37 | chapter = Tetrahalo Complexes of Dipositive Metals in the First Transition Series| isbn = 978-0-470-13240-1 }}

The anhydrous FeCl₂, which is soluble in THF, is a standard precursor in organometallic synthesis. FeCl₂ is used to generate NHC complexes in situ for cross coupling reactions.{{cite journal|journal=Org. Synth.|year=2014|volume=91|pages=83–92|doi=10.15227/orgsyn.091.0083|title=Cross-Coupling of Alkenyl/Aryl Carboxylates with Grignard Reagents via Fe-Catalyzed C-O Bond Activation|author=Bi-Jie Li |author2=Xi-Sha Zhang |author3=Zhang-Jie Shi |doi-access=free}}

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.{{cite journal|jstor = 25046917|title = The Use of Ferrous Chloride to Control Dissolved Sulfides in Interceptor Sewers|journal = Journal (Water Pollution Control Federation)|volume = 61|issue = 2|pages = 230–236|last1 = Jameel|first1 = Pervez|year = 1989}} 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. FeCl₂ finds some use as a reagent in organic synthesis.{{cite encyclopedia|author=Andrew D. White |author2=David G. Hilmey |encyclopedia=Encyclopedia of Reagents for Organic Synthesis|doi=10.1002/047084289X.ri055.pub2|year=2009|chapter=Iron(II) Chloride|isbn = 978-0-471-93623-7}}

Natural occurrence

Lawrencite, (Fe,Ni)Cl₂, is the natural counterpart, and a typically (though rarely occurring) meteoritic mineral.{{Cite web|url=https://www.mindat.org/min-2351.html|title=Lawrencite}} The natural form of the dihydrate is rokühnite - a very rare mineral.{{Cite web|url=https://www.mindat.org/min-3440.html|title=Rokühnite}} Related, but more complex (in particular, basic or hydrated) minerals are hibbingite, droninoite and kuliginite.