Manganese(III) fluoride

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Manganese(III) fluoride
Manganese(III) fluoride
Identifiers
CAS number 7783-53-1
PubChem 82213
ChemSpider 74193 YesY
RTECS number OP0882600
Jmol-3D images Image 1
Properties
Molecular formula MnF3
Molar mass 111.938 g/mol
Appearance purple-pink powder
hygroscopic
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
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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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[edit]

Synthesis[edit]

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[edit]

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.[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[edit]

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

3NaF + MnF3 → Na3MnF6

Other reaction conditions give compounds with anion formula MnF52- 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[edit]

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[edit]

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[edit]

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

References[edit]

  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[edit]

External links[edit]