Manganese(II) chloride is the di

chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...

salt of

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

, MnCl₂. This inorganic chemical 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 Manganese dioxide 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 is for dry-cel ...

with concentrated hydrochloric acid. :MnO₂ + 4 HCl → MnCl₂ + 2 H₂O + Cl₂ This reaction was once used for the manufacture of

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

. 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

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 Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

: :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-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 ...

s. The octahedron is completed by a pair of mutually trans

aquo ligand In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perch ...

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 In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perchlorat ...

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

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).html"_;"title="EDTA.html"_;"title="n(EDTA">n(EDTA)">EDTA.html"_;"title="n(EDTA">n(EDTA)sup>−,_[Mn(cyanide.html" ;"title="EDTA">n(EDTA).html" ;"title="EDTA.html" ;"title="n(EDTA">n(EDTA)">EDTA.html" ;"title="n(EDTA">n(EDTA)sup>−, [Mn(cyanide">CN)₆]³⁻, and [Mn(acetylacetonate)₃]. Triphenylphosphine forms a labile 2:1 adduct: :MnCl₂ + 2 triphenylphosphine, Ph₃P → nCl₂(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 ...

tetrahydrofuran Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity. It is ma ...

(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.

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 Manganism or manganese poisoning is a toxic condition resulting from chronic exposure to manganese. It was first identified in 1837 by James Couper. Signs and symptoms Chronic exposure to excessive manganese levels can lead to a variety of psyc ...

, 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