MNF

MNF may refer to:

Manganese(III) fluoride

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.

Synthesis, structure and reactions

Synthesis

MnF₃ can be prepared by treating a solution of MnF₂ in hydrogen fluoride with fluorine:

It 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.

Manganese(IV) fluoride

Manganese tetrafluoride, MnF₄, is the highest fluoride of manganese. It is a powerful oxidizing agent and is used as a means of purifying elemental fluorine.

Preparation

Manganese tetrafluoride was first unequivocally prepared in 1961 by the reaction of manganese(II) fluoride (or other Mn^II compounds) with a stream of fluorine gas at 550 °C: the MnF₄ sublimes into the gas stream and condenses onto a cold finger. This is still the commonest method of preparation, although the sublimation can be avoided by operating at increased fluorine pressure (4.5–6 bar at 180–320 °C) and mechanically agitating the powder to avoid sintering of the grains. The reaction can also be carried out starting from manganese powder in a fluidized bed.

Other preparations of MnF₄ include the fluorination of MnF₂ with krypton difluoride, or with F₂ in liquid hydrogen fluoride solution under ultraviolet light. Manganese tetrafluoride has also been prepared (but not isolated) in an acid–base reaction between antimony pentafluoride and K₂MnF₆ as part of a chemical synthesis of elemental fluorine.