Manganese(II) chloride is the di chloride salt of manganese, MnCl₂. This

inorganic chemical In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistr ...

exists in the

anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...

form, as well as the di

hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

(MnCl₂·2H₂O) and tetrahydrate (MnCl₂·4H₂O), with the tetrahydrate being the most common form. Like many Mn(II) species, these salts are pink, with the paleness of the color being characteristic of transition metal complexes with

high spin Spin states when describing transition metal coordination complexes refers to the potential spin configurations of the central metal's d electrons. For several oxidation states, metals can adopt high-spin and low-spin configurations. The ambiguity o ...

d⁵ configurations.

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.. Manganous chloride anh

In the laboratory, manganese chloride can be prepared by treating manganese metal or

manganese(II) carbonate Manganese carbonate is a compound with the chemical formula Mn CO3. Manganese carbonate occurs naturally as the mineral rhodochrosite but it is typically produced industrially. It is a pale pink, water-insoluble solid. Approximately 20,000 metr ...

with hydrochloric acid: :Mn + 2 HCl + 4 H₂O → MnCl₂(H₂O)₄ + H₂ :MnCO₃ + 2 HCl + 3 H₂O → MnCl₂(H₂O)₄ + CO₂

Structures

Anhydrous MnCl₂ adopts a layered

cadmium chloride Cadmium chloride is a white crystalline compound of cadmium and chloride, with the formula CdCl2. This salt is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. The crystal structure of cadmium chloride (describe ...

-like structure. The tetrahydrate consists of octahedral ''

cis Cis or cis- may refer to: Places * Cis, Trentino, in Italy * In Poland: ** Cis, Świętokrzyskie Voivodeship, south-central ** Cis, Warmian-Masurian Voivodeship, north Math, science and biology * cis (mathematics) (cis(''θ'')), a trigonome ...

''-Mn(H₂O)₄Cl₂ molecules. The trans isomer, which is metastable, is also known. The dihydrate MnCl₂(H₂O)₂ is a

coordination polymer A coordination polymer is an inorganic or organometallic polymer structure containing metal cation centers linked by ligands. More formally a coordination polymer is a coordination compound with repeating coordination entities extending in 1, 2, o ...

. Each Mn center is coordinated to four doubly

bridging chloride ligand In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually r ...

s. The octahedron is completed by a pair of mutually trans aquo ligands. MX2(H2O)2

Chemical properties

The hydrates dissolve in water to give mildly acidic solutions with a pH of around 4. These solutions consist of the metal aquo complex n(H₂O)₆sup>2+. It is a weak

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

, reacting with chloride ions to produce a series of salts containing the following ions nCl₃sup>−, nCl₄sup>2−, and nCl₆sup>4−. Upon treatment with typical organic ligands, manganese(II) undergoes oxidation by air to give Mn(III) complexes. Examples include n(EDTA)">EDTA.html" ;"title="n(EDTA">n(EDTA)sup>−, [Mn(cyanide">CN)₆">EDTA">n(EDTA)">EDTA.html" ;"title="n(EDTA">n(EDTA)sup>−, [Mn(cyanide">CN)₆sup>3−, and [Mn(acetylacetonate)₃]. Triphenylphosphine forms a labile 2:1 adduct: :MnCl₂ + 2 triphenylphosphine, Ph₃P → [MnCl₂(Ph₃P)₂] Anhydrous manganese(II) chloride serves as a starting point for the synthesis of a variety of

organomanganese compound Organomanganese chemistry is the chemistry of organometallic compounds containing a carbon to manganese chemical bond. In a 2009 review, Cahiez et al. argued that as manganese is cheap and benign (only iron performs better in these aspects), organo ...

s. For example,

manganocene Manganocene or bis(cyclopentadienyl)manganese(II) is an organomanganese compound with the formula n(C5H5)2sub>n. It is a thermochromic solid that degrades rapidly in air. Although the compound is of little utility, it is often discussed as an ...

is prepared by reaction of MnCl₂ with a solution of

sodium cyclopentadienide Sodium cyclopentadienide is an organosodium compound with the formula C5H5Na. The compound is often abbreviated as NaCp, where Cp− is the cyclopentadienide anion. Sodium cyclopentadienide is a colorless solid, although samples often are pi ...

in tetrahydrofuran (THF). :MnCl₂ + 2 NaC₅H₅ → Mn(C₅H₅)₂ + 2 NaCl Similar reactions are used in the preparation of the antiknock compound

methylcyclopentadienyl manganese tricarbonyl Methylcyclopentadienyl manganese tricarbonyl (MMT or MCMT) is an organomanganese compound with the formula (C5H4CH3)Mn(CO)3. Initially marketed as a supplement for use in leaded gasoline, MMT was later used in unleaded gasoline to increase the o ...

. Manganese chloride is a precursor to organomanganese reagents in organic chemistry. Manganese chloride is mainly used in the production of dry cell batteries.

Magnetism

Manganese(II) salts are paramagnetic. As such the presence of such salts profoundly affect

NMR spectra Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fiel ...

Natural occurrence

Scacchite is the natural, anhydrous form of manganese(II) chloride. The only other currently known mineral systematized as manganese chloride is kempite - a representative of the atacamite group, a group of hydroxide-chlorides.

Precautions

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

References

External links

National Pollutant Inventory: Manganese and compounds Fact Sheet
{{Chlorides Chlorides Manganese(II) compounds Metal halides