Manganese(III) fluoride

Manganese trifluoride is the chemical compound with the formula MnF3. This purplish solid is highly reactive, being unstable in moist air and liberating F2 upon heating. MnF3 is useful for converting hydrocarbons into fluorocarbons, i.e. it is a fluorination agent.
 * R3C-H +  2 MnF3  &rarr;  R3C-F  +  HF  +  2MnF2

A related fluorinating reagent is CoF3.

Synthesis and reactions
MnF3 can be prepared by treating a solution of MnF2 in anhydrous hydrogen fluoride with fluorine:
 * MnF2 +  0.5 F2  &rarr;  MnF3

In the crystalline state, MnF3 resembles vanadium(III) fluoride: both feature octahedal 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 A.   Jahn-Teller distortions are characteristic of the presence of four d-electrons in the valence shell.

Related Mn(III) and Mn(IV) compounds
The fluorination of MnF2 in HF, if conducted in the presence of UV-irradiation, gives MnF4. This tetrafluoride is a relatively rare Mn(IV) species, the most famous example being manganese dioxide.

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 bottles.