Chemical compound
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Chemical compound
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 forms a hydrate and many derivatives.
Synthesis, structure and reactions.
MnF3 can be prepared by treating a solution of MnF2 in hydrogen fluoride with fluorine:
MnF2 + 0.5 F2 → MnF3
It can also be prepared by the reaction of elemental fluorine with a manganese(II) halide at ~250 °C.
Structure.
Like vanadium(III) fluoride, MnF3 features 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 exists as two polymorphs, with space groups P21/c and P21/a. Each consists of the salt [Mn(H2O)4F2]+[Mn(H2O)2F4]− ).
Reactions.
MnF3 is Lewis acidic and forms a variety of derivatives. One example is K2MnF3(SO4). MnF3 reacts with sodium fluoride to give the octahedral hexafluoride:
3NaF + MnF3 → Na3MnF6
Related reactions salts of the anions MnF52− or MnF4−. These anions adopt chain and layer structures respectively, with bridging fluoride. Manganese remains 6 coordinate, octahedral, and trivalent in all of these materials.
Manganese(III) fluoride fluorinates organic compounds including aromatic hydrocarbons, cyclobutenes, and fullerenes.
On heating, MnF3 decomposes to manganese(II) fluoride.
MnF3 is a source of MnCl3 complexes by reaction with bismuth trichloride.
References.
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