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Manganese(II) chloride
Encyclopedia
Manganese chloride describes a series of compounds with the formula Mn
Cl
2(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.
with concentrated hydrochloric acid.
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.
In the laboratory, manganese chloride can be prepared by treating manganese
metal or manganese(II) carbonate
and hydrochloric acid
:
-like structure. The tetrahydrate consists of octahedral trans-Mn(H2O)4Cl2 molecules 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 polymer
ic.
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
:
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
.
.
to determine the size and lamellarity of phospholipid
vesicles. 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.
, or manganese poisoning, can be caused by long-term exposure to manganese dust or fumes.
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
Cl
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
2(H2O)x, where the value of x can be 0, 2, or 4. The tetrahydrate
Water of crystallization
In crystallography, water of crystallization or water of hydration or crystallization water is water that occurs in crystals. Water of crystallization is necessary for the maintenance of crystalline properties, but capable of being removed by sufficient heat...
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.
Preparation
Manganese chloride is produced by treating manganese(IV) oxideManganese(IV) oxide
Manganese oxide is the inorganic compound with the formula . This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for MnO2 is for dry-cell batteries, such as the alkaline battery and the...
with concentrated hydrochloric acid.
- MnO2 + 4 HCl → MnCl2 + 2 H2O + Cl2
This reaction was once used for the manufacture of chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
. By carefully neutralizing the resulting solution with MnCO3, one can selectively precipitate iron salts, which are common impurities in manganese dioxide.
In the laboratory, manganese chloride can be prepared by treating manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
metal or manganese(II) carbonate
Manganese(II) carbonate
Manganese carbonate is a compound with the chemical formula MnCO3. Manganese carbonate occurs naturally as the mineral rhodochrosite. Approximately 20,000 metric tonnes were produced in 2005.-Production and uses:...
and hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric 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 chlorideCadmium chloride
Cadmium chloride is a white crystalline compound of cadmium and chlorine, with the formula CdCl2. It is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. Although it is considered to be ionic, it has considerable covalent character to its bonding...
-like structure. The tetrahydrate consists of octahedral trans-Mn(H2O)4Cl2 molecules The hydrates dissolve in water to give mildly acidic solutions with a pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
of around 4.
It is a weak Lewis acid
Lewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
, reacting with chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
ions to produce a series of solids containing the following ions [MnCl3]
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
ic.
Upon treatment with typical organic ligands, manganese(II) undergoes oxidation by air to give Mn(III) complexes
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
. Examples include [Mn(EDTA
EDTA
Ethylenediaminetetraacetic acid, widely abbreviated as EDTA , is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand...
)]
Cyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....
)6]3
Triphenylphosphine
Triphenylphosphine is a common organophosphorus compound with the formula P3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature...
forms a labile 2:1 adduct
Adduct
An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species...
:
- MnCl2 + 2 Ph3PTriphenylphosphineTriphenylphosphine is a common organophosphorus compound with the formula P3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature...
→ [MnCl2(Ph3P)2]
Anhydrous manganese(II) chloride serves as a starting point for the synthesis of a variety of manganese compounds. For example, manganocene
Manganocene
Manganocene or bismanganese is an organometallic compound of manganese. It is a metallocene.In the solid state, manganocene adopts a polymeric structure with every manganese atom coordinated by three cyclopentadienyl ligands, two of which are bridging ligands...
is prepared by reaction of MnCl2 with a solution of sodium cyclopentadienide
Sodium cyclopentadienide
Sodium cyclopentadienide is an organosodium compound with the formula C5H5Na. The compound is often abbreviated as NaCp or CpNa, where Cp− is the cyclopentadienide anion. Cp is also used as an abbreviation for the cyclopentadienyl ligand in coordination chemistry.-Preparation:Sodium...
in THF
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
.
- 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 tricarbonylMethylcyclopentadienyl manganese tricarbonyl
Methylcyclopentadienyl manganese tricarbonyl is an organomanganese compound with the formula Mn3. Marketed initially in 1958 as a supplement to the gasoline additive tetraethyl lead to increase the fuel's octane rating, MMT was later used in unleaded gasoline...
.
Vesicle characterization with 31P-NMR
MnCl2 is used in 31P-NMRPhosphorus-31 NMR
Phosphorus-31 NMR spectroscopy is an analytical technique. Solution 31P-NMR is one of the more routine NMR techniques because 31P has an isotopic abundance of 100% and a relatively high magnetogyric ratio. The 31P nucleus also has a spin of ½, making spectra relatively easy to interpret...
to determine the size and lamellarity of phospholipid
Phospholipid
Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Most phospholipids contain a diglyceride, a phosphate group, and a simple organic molecule such as choline; one exception to this rule is sphingomyelin, which is derived from...
vesicles. When manganese chloride is added to a vesicular solution, Mn2+ paramagnetic ions are released, perturbing the relaxation time
Relaxation (NMR)
In nuclear magnetic resonance spectroscopy and magnetic resonance imaging the term relaxation describes several processes by which nuclear magnetization prepared in a non-equilibrium state return to the equilibrium distribution. In other words, relaxation describes how fast spins "forget" the...
of the phospholipids' phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
groups and broadening the resulting 31P resonance signal
Nuclear magnetic resonance
Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...
. Only phospholipids located in the outermost monolayer
Monolayer
- Chemistry :A Langmuir monolayer or insoluble monolayer is a one-molecule thick layer of an insoluble organic material spread onto an aqueous subphase. Traditional compounds used to prepare Langmuir monolayers are amphiphilic materials that possess a hydrophilic headgroup and a hydrophobic tail...
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.
Precautions
ManganismManganism
Manganism or manganese poisoning is a toxic condition resulting from chronic exposure to manganese and first identified in 1837 by James Couper.- Presentation :...
, or manganese poisoning, can be caused by long-term exposure to manganese dust or fumes.