Manganese(II) chloride

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Manganese(II) chloride
Manganous chloride anh.jpg
Anhydrous
Manganese(II) chloride tetrahydrate.jpg
Tetrahydrate
Identifiers
CAS number 7773-01-5 YesY, 38639-72-4 (dihydrate), 13446-34-9 (tetrahydrate)
PubChem 24480
ChemSpider 22888 YesY
UNII 6YB4901Y90 YesY
ChEMBL CHEMBL1200693 N
RTECS number OO9625000
Jmol-3D images Image 1
Properties
Molecular formula MnCl2
Molar mass 125.844 g/mol (anhydrous)
161.874 g/mol (dihydrate)
197.91 g/mol (tetrahydrate)
Appearance pink solid (tetrahydrate)
Density 2.977 g/cm3 (anhydrous)
2.27 g/cm3 (dihydrate)
2.01 g/cm3 (tetrahydrate)
Melting point 654 °C (1,209 °F; 927 K) (anhydrous)
dihydrate dehydrates at 135 °C
tetrahydrate dehydrates at 58 °C
Boiling point 1,225 °C (2,237 °F; 1,498 K)
Solubility in water 63.4 g/100 ml (0 °C)
73.9 g/100 ml (20 °C)
88.5 g/100 ml (40 °C)
123.8 g/100 ml (100 °C)
Solubility soluble in pyridine, ethanol
insoluble in ether
Structure
Crystal structure CdCl2
Coordination
geometry
octahedral
Hazards
EU Index Not listed
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
LD50 250-275 mg/kg (rat, oral)
Related compounds
Other anions Manganese(II) fluoride
Manganese(II) bromide
Manganese(II) iodide
Other cations Manganese(III) chloride
Technetium(IV) chloride
Rhenium(III) chloride
Rhenium(IV) chloride
Rhenium(V) chloride
Rhenium(VI) chloride
Related compounds Chromium(II) chloride
Iron(II) chloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Manganese(II) chloride describes a series of compounds with the formula MnCl2(H2O)x, where the value of x can be 0, 2, or 4. The tetrahydrate is the most common form of "manganese(II) chloride" and is represented by the formula MnCl2·4H2O, but the anhydrous form and dihydrate MnCl2·2H2O are also known. 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.[1]

Preparation[edit]

Manganese chloride is produced by treating manganese(IV) oxide with concentrated hydrochloric acid.

MnO2 + 4 HCl → MnCl2 + 2 H2O + Cl2

This reaction was once used for the manufacture of chlorine. By carefully neutralizing the resulting solution with MnCO3, one can selectively precipitate iron salts, which are common impurities in manganese dioxide.[2]

In the laboratory, manganese chloride can be prepared by treating manganese metal or manganese(II) carbonate and hydrochloric acid:

Mn + 2 HCl → MnCl2 + H2
MnCO3 + 2 HCl → MnCl2 + H2O + CO2

Chemical properties[edit]

Anhydrous MnCl2 is a polymeric solid, which adopts a layered cadmium chloride-like structure. The tetrahydrate consists of octahedral trans-Mn(H2O)4Cl2 molecules[3] The hydrates dissolve in water to give mildly acidic solutions with a pH of around 4.

It is a weak Lewis acid, reacting with chloride ions to produce a series of solids containing the following ions [MnCl3], [MnCl4]2−, and [MnCl6]4−. Both [MnCl3] and [MnCl4]2− are polymeric.

Upon treatment with typical organic ligands, manganese(II) undergoes oxidation by air to give Mn(III) complexes. Examples include [Mn(EDTA)], [Mn(CN)6]3−, and [Mn(acetylacetonate)3]. Triphenylphosphine forms a labile 2:1 adduct:

MnCl2 + 2 Ph3P → [MnCl2(Ph3P)2]

Anhydrous manganese(II) chloride serves as a starting point for the synthesis of a variety of manganese compounds. For example, manganocene is prepared by reaction of MnCl2 with a solution of sodium cyclopentadienide in THF.

MnCl2 + 2 NaC5H5 → Mn(C5H5)2 + 2 NaCl

Applications[edit]

The main application is used in the production of dry cell batteries. It is the precursor to the antiknock compound methylcyclopentadienyl manganese tricarbonyl.[2]

Vesicle characterization with 31P-NMR[edit]

MnCl2 is used in 31P-NMR to determine the size and lamellarity of phospholipid vesicles.[4] When manganese chloride is added to a vesicular solution, Mn2+ paramagnetic ions are released, perturbing the relaxation time of the phospholipids' phosphate groups and broadening the resulting 31P resonance signal. Only phospholipids located in the outermost monolayer exposed to Mn2+ experience this broadening. The effect is negligle for multilamellar vesicles, but for large unilamellar vesicles, a ~50% reduction in signal intensity is observed.[5]

Precautions[edit]

Manganism, or manganese poisoning, can be caused by long-term exposure to manganese dust or fumes.

References[edit]

  1. ^ N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
  2. ^ a b Reidies, Arno H. (2002), "Manganese Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a16_123, ISBN 3-527-30385-5 .
  3. '^ A. F. Wells, Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
  4. ^ Frohlich, Margret; Brecht, Volker; Peschka-Suss, Regine (January 2001), "Parameters influencing the determination of liposome lamellarity by 31P-NMR", Chemistry and Physics of Lipids 109 (1): 103–112, doi:10.1016/S0009-3084(00)00220-6, PMID 11163348 
  5. ^ Hope, M; Bally, M; Webb, G; Cullis, P (received = April 10, 1984), "Production of large unilamellar vesicles by a rapid extrusion procedure. Characterization of size distribution, trapped volume and ability to maintain a membrane potential", Biochimica et Biophysica Acta 812: 55–65, doi:10.1016/0005-2736(85)90521-8  Check date values in: |date= (help)

External links[edit]