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| Names | |||
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| IUPAC names Iron(II) chloride Iron dichloride | |||
| Other names Ferrous chloride Rokühnite | |||
| Identifiers | |||
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3D model (JSmol) |
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| ChEBI | |||
| ChemSpider |
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| ECHA InfoCard | 100.028.949 | ||
| EC Number |
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| RTECS number |
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| UNII | |||
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| Properties | |||
| FeCl2 | |||
| Molar mass | 126.751 g/mol (anhydrous) 198.8102 g/mol (tetrahydrate) | ||
| Appearance | Tan 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 inTHF | Soluble | ||
| logP | −0.15 | ||
| +14750·10−6 cm3/mol | |||
| Structure | |||
| Monoclinic | |||
| Octahedral at Fe | |||
| Pharmacology | |||
| B03AA05 (WHO) | |||
| Hazards | |||
| GHS labelling: | |||
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| Danger | |||
| H290,H302,H315,H317,H318,H412 | |||
| P234,P261,P264,P264+P265,P270,P272,P273,P280,P301+P317,P302+P352,P305+P354+P338,P317,P321,P330,P333+P317,P362+P364,P390,P501 | |||
| NFPA 704 (fire diamond) | |||
| NIOSH (US health exposure limits): | |||
REL (Recommended) | TWA 1 mg/m3[1] | ||
| Safety data sheet (SDS) | Iron (II) chloride MSDS | ||
| Related compounds | |||
Otheranions | Iron(II) fluoride Iron(II) bromide Iron(II) iodide | ||
Othercations | Cobalt(II) chloride Manganese(II) chloride Copper(II) chloride | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Iron(II) chloride, also known asferrous chloride, is thechemical compound of formula FeCl2. It is aparamagnetic solid with a high melting point. The compound is white, but typical samples are often off-white. FeCl2crystallizes from water as the greenishtetrahydrate, 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.
Hydrated forms of ferrous chloride are generated by treatment of wastes fromsteel production withhydrochloric acid. Such solutions are designated "spent acid," or "pickle liquor" especially when the hydrochloric acid is not completely consumed:
The production of ferric chloride involves the use of ferrous chloride. Ferrous chloride is also a byproduct from the production of titanium, since sometitanium ores contain iron.[3]
Ferrous chloride is prepared by addition of iron powder to a solution ofhydrochloric acid in methanol. This reaction gives the methanol solvate of the dichloride, which upon heating in a vacuum at about 160 °C converts toanhydrous FeCl2.[4] The net reaction is shown:
FeBr2 and FeI2 can be prepared analogously.
An alternative synthesis of anhydrous ferrous chloride is the reduction ofFeCl3 withchlorobenzene:[5]
For the preparation offerrocene ferrous chloride is generatedin situ by comproportionation of FeCl3 with iron powder intetrahydrofuran (THF).[6] Ferric chloride decomposes to ferrous chloride at high temperatures.
The dihydrate, FeCl2(H2O)2, crystallizes from concentrated hydrochloric acid.[7] The dihydrate is acoordination polymer. Each Fe center is coordinated to four doublybridging chloride ligands. The octahedron is completed by a pair of mutually transaquo ligands.[8]
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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 generateNHC complexes in situ forcross coupling reactions.[11]
Unlike the relatedferrous sulfate andferric chloride, ferrous chloride has few commercial applications. Aside from use in the laboratory synthesis of iron complexes, ferrous chloride serves as a coagulation andflocculation agent inwastewater treatment, especially for wastes containingchromate orsulfides.[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 areagent inorganic synthesis.[13]
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 arehibbingite,droninoite andkuliginite.
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