Formula MnF3 Density 3.54 g/cm³ | Molar mass 111.938 g/mol | |
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Related compounds Appearance purple-pink powder; hygroscopic | ||
Manganese(III) fluoride (also known as Manganese trifluoride) is the inorganic compound with the formula MnF3. This red/purplish solid is useful for converting hydrocarbons into fluorocarbons, i.e., it is a fluorination agent. It also forms a hydrate.
Contents
Synthesis
MnF3 can be prepared by treating a solution of MnF2 in hydrogen fluoride with fluorine:
MnF2 + 0.5 F2 → MnF3It can also be prepared by the reaction of elemental fluorine with a manganese(II) halide at ~250 °C.
Structure
In the crystalline state, MnF3 resembles vanadium(III) fluoride: both feature octahedral metal centers with the same average M-F bond distances. In the Mn compound, however, is distorted (and hence a monoclinic unit cell vs. a higher symmetry one) due to the Jahn-Teller effect, with pairs of Mn-F distances of 1.79, 1.91, 2.09 Å.
The hydrate MnF3.3H2O is obtained by crystallisation of MnF3 from hydrofluoric acid. The hydrate is unusual in that it forms two different structures (both based on [Mn(H2O)4F2]+ [Mn(H2O)2F4]− ), which have space groups P21/c and P21/a.
Reactions
MnF3 reacts with sodium fluoride to give the octahedral hexafluorate anion:
3NaF + MnF3 → Na3MnF6Other reaction conditions give compounds with anion formula MnF52− or MnF4−. These anions are chain and layer structures respectively, with bridging fluorine. Manganese remains 6 coordinate, octahedral, and trivalent in all these materials.
Manganese(III) fluoride fluorinates organic compounds including aromatic hydrocarbons, cyclobutenes, and fullerenes.
On heating, MnF3 decomposes to manganese(II) fluoride.
Related Mn(III) compounds
Other manganese(III) compounds include manganese(III) acetate (CAS# 993-02-2), manganese acetylacetonate (CAS# 14284-89-0), Both are employed as oxidants in organic synthesis. MnF3 is Lewis acidic and forms a variety of derivatives. Two examples are K2MnF3(SO4) and K2MnF5.
Safety considerations
Like other reactive inorganic fluorides, MnF3 should be stored in a polyethylene bottle and contact with skin or any other moist area avoided due to the formation of Hydrofluoric acid on hydrolysis.