Manganese(III) fluoride (also known as Manganese trifluoride) is the inorganic compound with the formula MnF<sub>3</sub>. 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.
MnF<sub>3</sub> can be prepared by treating a solution of MnF<sub>2</sub> in hydrogen fluoride with fluorine:
It can also be prepared by the reaction of elemental fluorine with a manganese(II) halide at ~250 ðC.
Like vanadium(III) fluoride, MnF<sub>3</sub> 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 ÃÂ .
The hydrate MnF<sub>3</sub><sup>.</sup>3H<sub>2</sub>O is obtained by crystallisation of MnF<sub>3</sub> from hydrofluoric acid. The hydrate exists as two polymorphs, with space groups P2<sub>1</sub>/c and P2<sub>1</sub>/a. Each consists of the salt [Mn(H<sub>2</sub>O)<sub>4</sub>F<sub>2</sub>]<sup>+</sup>[Mn(H<sub>2</sub>O)<sub>2</sub>F<sub>4</sub>]<sup>âÂÂ</sup> ).
MnF<sub>3</sub> is Lewis acidic and forms a variety of derivatives. One example is K<sub>2</sub>MnF<sub>3</sub>(SO<sub>4</sub>). MnF<sub>3</sub> reacts with sodium fluoride to give the octahedral hexafluoride:
Related reactions salts of the anions MnF<sub>5</sub><sup>2âÂÂ</sup> or MnF<sub>4</sub><sup>âÂÂ</sup>. 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, MnF<sub>3</sub> decomposes to manganese(II) fluoride.
MnF<sub>3</sub> is a source of MnCl<sub>3</sub> complexes by reaction with bismuth trichloride.