Manganese(II) chloride

Manganese(II) chloride
Anhydrous
Tetrahydrate
IUPAC name Manganese(II) chloride Manganese dichloride
Other names Manganous chloride
Identifiers
CAS number	7773-01-5 Y, 38639-72-4 (dihydrate), 13446-34-9 (tetrahydrate)
PubChem	24480
ChemSpider	22888 Y
UNII	6YB4901Y90 Y
ChEMBL	CHEMBL1200693 N
RTECS number	OO9625000
Jmol-3D images	Image 1
SMILES Cl[Mn]Cl
InChI InChI=1S/2ClH.Mn/h2*1H;/q;;+2/p-2 Y Key: GLFNIEUTAYBVOC-UHFFFAOYSA-L Y
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	2.98 g/cm3 (anhydrous) 2.27 g/cm3 (dihydrate) 2.01 g/cm3 (tetrahydrate)
Melting point	654 °C (anhydrous) dihydrate dehydrates at 135 °C tetrahydrate dehydrates at 58 °C
Boiling point	1225 °C
Solubility in water	63.4 g/100 ml (0°C) 73.9 g/100 ml (20°C) 88.5 g/100 ml (40°C) 115.0 g/100 ml (100°C)
Structure
Crystal structure	CdCl2
Coordination geometry	octahedral
Hazards
EU Index	Not listed
NFPA 704	0 1 0
Flash point	Non-flammable
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
N chloride (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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". MnCl₂·4H₂O, but the anhydrous form and dihydrate MnCl₂·2H₂O are also known. Like many Mn(II) species, these salts are pink, the paleness of the color being characteristic of transition metal complexes with high spin d⁵ configurations.^[1]

Preparation

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

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

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

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

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

References

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, http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T2N-423J9WK-9&_user=10&_coverDate=01/31/2001&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1527591417&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7433836d10ceaa1aee850a98fefa62dd&searchtype=a 
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, http://www.islandnet.com/~prc/PDFs/073.pdf 

External links

• National Pollutant Inventory: Manganese and compounds Fact Sheet