Manganese(II) chloride

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Manganese(II) chloride (MnCl₂) is a pink salt derived from the elments manganese and chlorine. It occurs naturally as the rare mineral scacchite. Most commonly, the term "manganese(II) chloride" refers to the tetrahydrate trans-Mn(H₂O)₄Cl₂. Mn(H₂O)₂Cl₂ is also known. All such Mn(II) species are characteristically pink, the paleness of the color being attributed to high spin d⁵ configuration of octahedral Mn(II).

Contents

1 Preparation
2 Chemical properties
3 Precautions
4 Suppliers/Manufacturers
5 References
6 External links

Preparation

Manganese(II) chloride may be prepared by treating manganese metal or manganese(II) carbonate with hydrochloric acid:

Mn + 2 HCl → MnCl₂ + H₂

MnCO₃ + 2 HCl → MnCl₂ + H₂O + CO₂

It is also produced when manganese(IV) oxide is heated with concentrated hydrochloric acid; this reaction was formerly used for the manufacture of chlorine.

MnO₂ + 4 HCl → MnCl₂ + 2 H₂O + Cl₂

This reaction illustrates the oxidizing power of MnO₂ and the fact that oxides tend to exist in higher oxidaton states than chlorides.

Chemical properties

MnCl₂ is ionic, and it dissolves in water to give a solution with a pH of around 4.Such aqueous solutions are used to prepare a variety of manganese compounds, e.g.,

MnCl₂(aq) + K₂CO₃(aq) → MnCO₃(s) + 2 KCl(aq)

It is a weak Lewis acid, reacting chloride ion to produce a series of salts including polymeric [MnCl₃]^-, [MnCl₄]^2- , and [MnCl₆]^4-. It forms complexes with ligands such as triphenylphosphine (see "uses"):

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 may be prepared by reaction of MnCl₂ with cyclopentadienylsodium in THF.

Precautions

Manganism, or manganese poisoning, may be caused by long-term exposure to manganese dust or fumes. The symptoms resemble Parkinson's disease and are similar to those induced by lead poisoning, but may not appear for months or even years after exposure. There is no cure for manganism.

Suppliers/Manufacturers

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

[National Pollutant Inventory - Manganese and compounds Fact Sheet]

For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].

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