Preparation

Manganese(II) chloride is prepared by heating manganese(II) oxide, manganese dioxide, manganese(II) carbonate or manganese(II) hydroxide with hydrochloric acid: MnO2 + 4HCl → MnCl2 + 2H2O + Cl2 MnCO3 + HCl → MnCl2 + H2O + CO2 When the product mixture is evaporated below 58°C, the tetrahydrate salt, MnCl2?4H2O is obtained. Manganese(II) chloride is a by-product in the manufacture of chlorine from manganese dioxide and hydrochloric acid (the Weldon process). Anhydrous chloride can be prepared by heating manganese(II) oxide or manganese(II) carbonate with dry hydrogen chloride; or by burning the metal in chlorine at 700°C to 1,000°C. The anhydrous salt can also be obtained by slowly heating the tetrahydrate, MnCl2?4H2O in a rotary drier above 200°C or by dehydration in a stream of hydrogen chloride gas.

Reactions

Manganese(II) chloride forms double salts with alkali metal chlorides when mixed in stoichiometric amounts. Such double salts, which can decompose in water, may have compositions like KMnCl3 or K2MnCl4. Manganese(II) chloride forms adducts with ammonia, hydroxylamine and many other nitrogen compounds. Many adducts are stable at ordinary temperatures. Examples are MnCl2?6NH3 and MnCl2?2NH2OH. An aqueous solution can readily undergo double decomposition reactions with soluble salts of other metals, producing precipitates of insoluble salts of Mn(II) or other metals.

Safety Profile

Poison by intraperitoneal, subcutaneous, intramuscular, intravenous, and parenteral routes. Moderately toxic by ingestion. Experimental teratogenic and reproductive effects. Questionable carcinogen with experimental carcinogenic data. Mutation data reported. Explosive reaction when heated with zinc foil. Reacts violently with potassium or sodium. When heated to decomposition it emits toxic fumes of Cl-. See also MANGANESE COMPOUNDS and CHLORIDES.

Physical Properties

The anhydrous chloride is a pink solid; cubic crystals; deliquescent; density 2.977 g/cm3 at 25°C; melts at 650°C; vaporizes at 1,190°C; very soluble in water (~72g/100 mL at 25°C); soluble in alcohol; insoluble in ether. The tetrahydrate has a rose color; monoclinic crystal structure; deliquescent; density 2.01 g/cm3; melts at 58°C; loses one molecule of water at 106°C and all water at 198°C; highly soluble in water (151 g/100mL at 8°C) and extremely soluble in boiling water (656 g/100mL at 100°C); soluble in ethanol; insoluble in ether.

General Description

Manganese (II) chloride (MnCl2) might play a key role in integrin activation. Manganese is indispensable for brain function and is an essential cofactor for several key enzymes like superoxide dismutase and enzymes involved in neurotransmitter synthesis. Manganese can modulate iron and calcium homeostasis. Manganese is also used in the magnetic resonance imaging to increase contrast while examining neuronal connections and brain cytoarchitecture. High levels of manganese is toxic to central nervous system and causes Parkinson′s like symptoms called as manganism. MnCl2 has been used in reverse transcription reaction mix to enhance the template-switching efficiency.