Manganese(III) fluoride

Manganese(III) fluoride
IUPAC name Manganese(III) fluoride
Other names Manganese trifluoride, manganic fluoride
Identifiers
CAS number	7783-53-1
PubChem	522682
ChemSpider	74193 Y
RTECS number	OP0882600
Jmol-3D images	Image 1
SMILES [Mn+3].[F-].[F-].[F-]
InChI InChI=1S/3FH.Mn/h3*1H;/q;;;+3/p-3 Y Key: SRVINXWCFNHIQZ-UHFFFAOYSA-K Y InChI=1/3FH.Mn/h3*1H;/q;;;+3/p-3 Key: SRVINXWCFNHIQZ-DFZHHIFOAX
Properties
Molecular formula	MnF3
Molar mass	111.938 g/mol
Appearance	purple-pink powder
Density	3.54 g/cm3
Melting point	> 600 °C (decomp)
Solubility in water	hydrolysis
Structure
Crystal structure	Monoclinic, mS48
Space group	C2/c, No. 15
Coordination geometry	distorted octahedral
Hazards
R-phrases	8-20/21/22-36/37/38
S-phrases	17-26-36/37/39
Main hazards	toxic fumes
Related compounds
Other anions	manganese(III) oxide, manganese(III) acetate
Other cations	chromium(III) fluoride, iron(III) fluoride. cobalt(III) fluoride
Related compounds	manganese(II) fluoride, manganese(IV) fluoride
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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.^[1] 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:^[2]

MnF₂ + 0.5 F₂ → MnF₃

It can also be prepared by the reaction of elemental fluorine with a manganese(II) halide at ~250 °C.^[3]

Structure

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 Å.^[4][5][6]

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.^[7]

Reactions

MnF₃ reacts with sodium fluoride to give the octahedral hexafluorate anion:^[3]:

3NaF + MnF₃ → Na₃MnF₆

Other reaction conditions give compounds with anion formula MnF₅^2- or MnF₄^-. These anions are chain and layer structures respectively, with bridging fluorine. Manganese remains 6 coordinate, octahedral, and trivalent in all these materials.^[3]

Manganese(III) fluoride fluorinates organic compounds including aromatic hydrocarbons,^[8] cyclobutenes,^[9] and fullerenes.^[10]

On heating, MnF₃ decomposes to manganese(II) fluoride.^[11][12]

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)^[13] 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.

See also

CoF₃, another fluorinating agent based on a transition metal in an oxidising +3 state.

References

1. ^ Burley, G. A.; Taylor, R. "Manganese(III) fluoride" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289
2. ^ Z. Mazej (2002). "Room temperature syntheses of MnF₃, MnF₄ and hexafluoromanganete(IV) salts of alkali cations". Journal of Fluorine Chemistry 114 (1): 75–80. doi:10.1016/S0022-1139(01)00566-8. 
3. ^ ^{a b c} Inorganic chemistry, Catherine E. Housecroft, A.G. Sharpe, pp.711-712, section Manganese (III) , googlebooks link
4. ^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
5. ^ Hepworth, M. A.; Jack, K. H.; Nyholm, R. S. (1957). "Interatomic Bonding in Manganese Trifluoride". Nature 179 (4552): 211–212. doi:10.1038/179211b0. 
6. ^ M. A. Hepworth, K. H. Jack (1957). "The crystal structure of manganese trifluoride, MnF₃". Acta Crystallographica 10 (5): 345–351. doi:10.1107/S0365110X57001024. 
7. ^ Structures of two polymorphs of MnF3·3H2O , Michel Molinier and Werner Massa , Journal of Fluorine Chemistry , Volume 57, Issues 1-3, April–June 1992, pp.139-146 , online abstract via www.sciencedirect.com
8. ^ Fluorination of p-chlorobenzotrifluoride by manganese trifluoride A. Kachanov, V. Kornilov, V.Belogay , Fluorine Notes :Vol. 1 (1) November–December 1998 , via notes.fluorine1.ru
9. ^ Fluorination of fluoro-cyclobutene with high-valency metal fluoride m Junji Mizukado, Yasuhisa Matsukawa, Heng-dao Quan, Masanori Tamura, Akira Sekiya , Journal of Fluorine Chemistry Volume 127, Issue 1, January 2006, Pages 79-84 , online abstract via www.sciencedirect.com
10. ^ Fluorination of the cubic and hexagonal C60 modifications by crystalline manganese trifluoride , Physics of the Solid State , Volume 44, Number 4 , 4/2002 , pp.629-630 , V.É. Aleshina, A.Ya. Borshchevskii, E.V. Skokan, I.V. Arkhangel’skii, A.V. Astakhov, N.B. Shustova , online abstract via www.springerlink
11. ^ Manganese; section Manganic Salts via www.1911encyclopedia.org
12. ^ In situ time-resolved X-ray diffraction study of manganese trifluoride thermal decomposition , J.V. Raua, V. Rossi Albertinib, N.S. Chilingarova, S. Colonnab, U. Anselmi Tamburini, Journal of Fluorine Chemistry 4506 (2001) 1–4 , online version
13. ^ Bhattacharjee, M. N; Chaudhuri, M. K. (1990). "Dipotassium Trifluorosulfatomanganate(III)". Inorg. Synth. 27: 312–313. doi:10.1002/9780470132586.ch61. 

Further reading

• Novel syntheses of some binary fluorides: the role of anhydrous hydrogen fluoride Acta Chim. Slov. 1999, 46(2), pp. 229–238 , Zoran Mazej, Karel Lutar and Boris Žemva
• Knudsen Cell mass spectrometry study of Manganese Trifluoride vaporisation , High temperature corrosion and materials chemistry IV: proceedings of the International Symposium , pp. 521–525 , google books

External links

• National Pollutant Inventory: Fluoride and compounds fact sheet
• National Pollutant Inventory: Manganese and compounds Fact Sheet