Manganese(III)_fluoride

Manganese(III) fluoride

Manganese(III) fluoride

Chemical compound

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.[2] It forms a hydrate and many derivatives.

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Synthesis, structure and reactions

MnF3 can be prepared by treating a solution of MnF2 in hydrogen fluoride with fluorine:[3]

MnF2 + 0.5 F2 → MnF3

It can also be prepared by the reaction of elemental fluorine with a manganese(II) halide at ~250 °C.[4]

Structure

Like vanadium(III) fluoride, MnF3 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 Å.[5][6][7]

The hydrate MnF3.3H2O is obtained by crystallisation of MnF3 from hydrofluoric acid. The hydrate exists as two polymorphs, with space groups P21/c and P21/a. Each consists of the salt [Mn(H2O)4F2]+[Mn(H2O)2F4]− ).[8]

Reactions

MnF3 is Lewis acidic and forms a variety of derivatives. One example is K2MnF3(SO4).[9] MnF3 reacts with sodium fluoride to give the octahedral hexafluoride:[4]

3NaF + MnF3 → Na3MnF6

Related reactions salts of the anions MnF52− or MnF4−. These anions adopt chain and layer structures respectively, with bridging fluoride. Manganese remains 6 coordinate, octahedral, and trivalent in all of these materials.[4]

Manganese(III) fluoride fluorinates organic compounds including aromatic hydrocarbons,[10] cyclobutenes,[11] and fullerenes.[12]

On heating, MnF3 decomposes to manganese(II) fluoride.[13][14]

MnF3 is a source of MnCl3 complexes by reaction with bismuth trichloride.[15]

See also

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

References

  1. [1]
    GHS: sigma-aldrich 339296 [dead link]
  2. [2]
    Burley, G. A.; Taylor, R. (2004). "Manganese(III) Fluoride". Encyclopedia of Reagents for Organic Synthesis. J. Wiley & Sons. doi:10.1002/047084289X.rn00411.
  3. [3]
    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.
  4. [4]
    Inorganic chemistry, Catherine E. Housecroft, A.G. Sharpe, pp.711-712, section Manganese (III) , googlebooks link
  5. [5]
    Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
  6. [6]
    Hepworth, M. A.; Jack, K. H.; Nyholm, R. S. (1957). "Interatomic Bonding in Manganese Trifluoride". Nature. 179 (4552): 211–212. Bibcode:1957Natur.179..211H. doi:10.1038/179211b0. S2CID 4208409.
  7. [7]
    M. A. Hepworth; K. H. Jack (1957). "The Crystal Structure of Manganese Trifluoride, MnF3". Acta Crystallographica. 10 (5): 345–351. doi:10.1107/S0365110X57001024.
  8. [8]
    Molinier Michel; Massa Werner (1992). "Structures of two polymorphs of MnF3·3H2O". Journal of Fluorine Chemistry. 57 (1–3): 139–146. doi:10.1016/S0022-1139(00)82825-0.
  9. [9]
    Bhattacharjee, M. N; Chaudhuri, M. K. (2007). "Dipotassium Trifluorosulfato‐Manganate(III)". Inorganic Syntheses. Vol. 27. pp. 312–313. doi:10.1002/9780470132586.ch61. ISBN 978-0-470-13258-6. {{cite book}}: |journal= ignored (help)
  10. [10]
    Fluorination of p-chlorobenzotrifluoride by manganese trifluoride Archived 2011-08-23 at the Wayback Machine A. Kachanov, V. Kornilov, V.Belogay , Fluorine Notes :Vol. 1 (1) November–December 1998 , via notes.fluorine1.ru
  11. [11]
    Junji Mizukado; Yasuhisa Matsukawa; Heng-dao Quan; Masanori Tamura; Akira Sekiya (2006). "Fluorination of Fluoro-Cyclobutene with High-Valency Metal Fluoride". Journal of Fluorine Chemistry. 127: 79–84. doi:10.1016/j.jfluchem.2005.10.007.
  12. [12]
    V. É. Aleshina; A. Ya. Borshchevskii; E. V. Skokan; I. V. Arkhangel'skii; A.V. Astakhov; N.B. Shustova (2002). "Fluorination of the Cubic and Hexagonal C60 Modifications by Crystalline Manganese Trifluoride". Physics of the Solid State. 44 (4): 629–630. Bibcode:2002PhSS...44..629A. doi:10.1134/1.1470543. S2CID 94250136.
  13. [13]
    Chisholm, Hugh, ed. (1911). "Manganese § Manganic Salts" . Encyclopædia Britannica. Vol. 17 (11th ed.). Cambridge University Press. p. 570.
  14. [14]
    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
  15. [15]
    Nachtigall, Olaf; Pataki, Astrid; Molski, Matthias; Lentz, Dieter; Spandl, Johann (2015). "Solvates of Manganese Trichloride Revisited - Synthesis, Isolation, and Crystal Structure of MnCl3(THF)3". Zeitschrift für Anorganische und Allgemeine Chemie. 641 (6): 1164–1168. doi:10.1002/zaac.201500106.

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