Manganese(II) chloride 1382162 215971940 2008-05-30T14:29:08Z Shoy 459990 fix link {{chembox new | ImageFile = Manganese(II)_chloride_tetrahydrate.jpg| | ImageSize = 200px | ImageName = Manganese(II) chloride tetrahydrate | IUPACName = Manganese(II) chloride | OtherNames = Manganous chloride | Section1 = {{Chembox Identifiers | Abbreviations = | CASNo = 7773-01-5 | EINECS = | PubChem = | SMILES = | InChI = | RTECS = | MeSHName = | ChEBI = | KEGG = | ATCCode_prefix = | ATCCode_suffix = | ATC_Supplemental =}} | Section2 = {{Chembox Properties | Formula = | MolarMass = anhydrous 125.844 g/mol; dihydrate 161.874 g/mol; tetrahydrate 197.91 g/mol | Appearance =pink solid<br/>(''tetrahydrate'') | Density = 3.0 g/cm³(solid) | MeltingPt = 654 °C | Melting_notes = | BoilingPt = 1225 °C | Boiling_notes = | Solubility = 72.3 g/100g | SolubleOther = | Solvent = | pKa = | pKb = }} | Section3 = {{Chembox Structure | CrystalStruct = [[Cadmium chloride#Crystal structure|CdCl<sub>2</sub>]] | Coordination = [[Octahedron|octahedral]] | MolShape = }} | Section7 = {{Chembox Hazards | EUClass = | EUIndex = | MainHazards = | NFPA-H = | NFPA-F = | NFPA-R = | NFPA-O = | RPhrases = | SPhrases = | RSPhrases = | FlashPt = | Autoignition = | ExploLimits = | PEL = }} | Section8 = {{Chembox Related | OtherAnions = [[Manganese(II) fluoride]]<br/>[[Manganese(II) bromide]]<br/>[[Manganese(II) iodide]] | OtherCations = [[Manganese(III) chloride]]<br/>[[Technetium(IV) chloride]]<br/>[[Rhenium(IV) chloride]] | OtherFunctn = | Function = | OtherCpds = [[Chromium(II) chloride]]<br/>[[Iron(II) chloride]]}} }} '''Manganese(II) chloride''' describes a series of compounds with the formula [[Manganese|Mn]][[chloride|Cl]]<sub>2</sub>(H<sub>2</sub>O)<sub>x</sub>, where the value of x can be 0, 2, or 4. The [[tetrahydrate]] is a pink [[salt]] that occurs naturally as the rare mineral [[scacchite]]. Most commonly, the term "manganese(II) chloride" refers to the [[water of crystallization|tetrahydrate]] MnCl<sub>2</sub>·4H<sub>2</sub>O, which consists of octahedral ''[[trans]]''-Mn(H<sub>2</sub>O)<sub>4</sub>Cl<sub>2</sub> molecules. The dihydrate MnCl<sub>2</sub>·2H<sub>2</sub>O is also known. Many Mn(II) species are characteristically pink, the paleness of the color being characteristic of transition metal complexes with [[high spin]] d<sup>5</sup> configurations. ==Preparation== Manganese(II) chloride can be prepared by treating [[manganese]] metal or [[manganese(II) carbonate]] with [[hydrogen chloride]] or [[hydrochloric acid]], depending on whether one seeks the anhydrous or hydrated forms: :Mn + 2 HCl → MnCl<sub>2</sub> + H<sub>2</sub> :MnCO<sub>3</sub> + 2 HCl → MnCl<sub>2</sub> + H<sub>2</sub>O + CO<sub>2</sub> It also forms when [[manganese(IV) oxide]] is heated with concentrated hydrochloric acid; this reaction was once used for the manufacture of [[chlorine]]. :MnO<sub>2</sub> + 4 HCl → MnCl<sub>2</sub> + 2 H<sub>2</sub>O + Cl<sub>2</sub> This reaction illustrates the oxidizing power of MnO<sub>2</sub> and the fact that oxides tend to exist in higher oxidation states than chlorides. ==Chemical properties== MnCl<sub>2</sub> is a polymeric solid which adopts a layered structure. The hydrates dissolve in water to give mildly acidic solutions with a [[pH]] of around 4. Such aqueous solutions are used to prepare a variety of manganese compounds, e.g., :MnCl<sub>2</sub>([[aqueous|aq]]) + [[potassium carbonate|K<sub>2</sub>CO<sub>3</sub>]](aq) → [[manganese(II) carbonate|MnCO<sub>3</sub>]]([[solid|s]]) + 2 [[potassium chloride|KCl]] In these equations, "MnCl<sub>2</sub>(aq)" refers to [Mn(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup>, which is the principal form of manganese in aqueous solutions of any manganese chloride. It is a weak [[Lewis acid]], reacting with [[chloride]] ions to produce a series of solids containing the following ions [MnCl<sub>3</sub>]<sup><nowiki>&minus;</nowiki></sup>, [MnCl<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup> , and [MnCl<sub>6</sub>]<sup>4<nowiki>&minus;</nowiki></sup>. Both [MnCl<sub>3</sub>]<sup><nowiki>&minus;</nowiki></sup> and [MnCl<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup> are [[polymer]]ic. Upon treatment with typical organic ligands, manganese(II) undergoes oxidation by air to give Mn(III) [[Complex (chemistry)|complexes]]. Examples include [Mn([[EDTA]]]<sup><nowiki>&minus;</nowiki></sup>, [Mn([[cyanide|CN]])<sub>6</sub>]<sup>3<nowiki>&minus;</nowiki></sup>, and [Mn([[acetylacetonate]])]<sub>3</sub>. [[Triphenylphosphine]] forms a labile 2:1 [[adduct]]: :MnCl<sub>2</sub> + 2 [[triphenylphosphine|Ph<sub>3</sub>P]] → [MnCl<sub>2</sub>(Ph<sub>3</sub>P)<sub>2</sub>] Anhydrous manganese(II) chloride serves as a starting point for the synthesis of a variety of manganese compounds. For example, [[metallocene|manganocene]] is prepared by reaction of MnCl<sub>2</sub> with a solution of [[cyclopentadienyl complex|sodium cyclopentadienide]] in [[Tetrahydrofuran|THF]]. :MnCl<sub>2</sub> + 2 NaC<sub>5</sub>H<sub>5</sub> → Mn(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 2 NaCl ==Paramagnetism== Manganese chloride is [[paramagnetic]], this fact is utilized when MnCl<sub>2</sub> is used as a contrast agent in [[MRI]] scanning. A dramatic example is using MnCl<sub>2</sub> to highlight neural pathways. ==Precautions== [[Manganism]], or manganese poisoning, can be caused by long-term exposure to manganese dust or fumes. ==References== # N. N. Greenwood, A. Earnshaw, ''Chemistry of the Elements'', 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997. # ''Handbook of Chemistry and Physics'', 71st edition, CRC Press, Ann Arbor, Michigan, 1990. # A. F. Wells, '''Structural Inorganic Chemistry'', 5th ed., Oxford University Press, Oxford, UK, 1984. # ''The Merck Index'', 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960. # Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5. ==External links== *[http://www.npi.gov.au/database/substance-info/profiles/52.html National Pollutant Inventory: Manganese and compounds Fact Sheet] [[Category:Chlorides]] [[Category:Manganese compounds]] [[Category:Metal halides]] [[de:Mangan(II)-chlorid]] [[it:Cloruro manganoso]] [[pl:Chlorek manganu(II)]] [[fi:Mangaani(II)kloridi]]