Manganese(IV) chloride
Chemical compound
From Wikipedia, the free encyclopedia
Manganese tetrachloride is a binary inorganic compound of manganese and chlorine with the chemical formula MnCl4.[1]
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| Cl4Mn | |
| Molar mass | 196.74 g·mol−1 |
| Appearance | brown solution |
| Melting point | −26 °C (−15 °F; 247 K)[citation needed] |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Synthesis
Pure manganese(IV) chloride has never been isolated.[2] According to Holleman and Wiberg (2016), it is likely to be an intermediate in the reaction between manganese dioxide and hydrogen chloride gas:[3]: 1907
- MnO2 + 4 HCl → MnCl4 + 2 H2O
- MnCl4 → MnCl2 + Cl2
Earlier works claim the compound is formed by treating manganese dioxide with cold, concentrated hydrochloric acid, resulting in a dark-brown solution.[4][5]
Other reactions with higher oxides are also possible:[6]
- Mn2O3 + 6 HCl → MnCl4 + MnCl2 + 3H2O
- Mn3O4 + 8 HCl → MnCl4 + 2 MnCl2 + 4H2O
MnCl4 is thermally unstable and liberates chlorine gas during these reactions and in solution at STP.[7]
Physical properties
The metal chloride is a highly unstable, dark-brown compound that easily decomposes, though a stable form can exist in solution at low temperatures, usually in the form of MnCl2−6 or MnCl−5 coordination-complex anions with excess HCl/H3O+ which then decompose favorably on formation of neutral MnCl4.[8] MnCl4 is often distinguished from the more common and stable manganese(II) chloride (MnCl2).[9]
Reactions
A reagent for the α-chlorination of enolizable ketones, derived from the reaction of manganese(IV) oxide with chlorotrimethylsilane ((CH3)3SiCl) or acetyl chloride (CH3COCl), is claimed to contain manganese(IV) chloride.[10][11]