Cobalt(III) fluoride

Last updated
Cobalt(III) fluoride
Cobalt(III) fluoride Aluminium-trifluoride-3D-polyhedra.png
Cobalt(III) fluoride
Cobalt(III) fluoride.png
Names
Other names
Cobalt trifluoride
Cobaltic fluoride
Cobalt fluoride
Cobaltic trifluoride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.045 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 233-062-4
PubChem CID
UNII
  • InChI=1S/Co.3FH/h;3*1H/q+3;;;/p-3 Yes check.svgY
    Key: WZJQNLGQTOCWDS-UHFFFAOYSA-K Yes check.svgY
  • InChI=1/Co.3FH/h;3*1H/q+3;;;/p-3
    Key: WZJQNLGQTOCWDS-DFZHHIFOAL
  • F[Co](F)F
Properties
CoF3
Molar mass 115.928 g/mol
Appearancebrown powder
Density 3.88 g/cm3
Melting point 927 °C (1,701 °F; 1,200 K)
reacts
+1900.0·10−6 cm3/mol
Structure
hexagonal
Hazards
GHS labelling: [1]
GHS-pictogram-acid.svg GHS-pictogram-skull.svg GHS-pictogram-exclam.svg
Danger
H301, H314, H317
P260, P264, P270, P272, P280, P301+P316, P301+P330+P331, P302+P352, P302+P361+P354, P304+P340, P305+P354+P338, P316, P321, P330, P333+P317, P362+P364, P363, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
3
0
2
Related compounds
Other anions
cobalt(III) oxide, cobalt(III) chloride
Other cations
iron(III) fluoride, rhodium(III) fluoride
Related compounds
 cobalt(II) fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Cobalt(III) fluoride (also known as cobalt trifluoride) is the inorganic compound with the formula CoF3. The compound exists in both hydrated and anhydrous forms, the latter being a hygroscopic brown solid. [2] It is used as a fluorinating agent in organofluorine synthesis. [3]

Contents

The related cobalt(III) chloride is also known but is extremely unstable. [4] Cobalt(III) bromide and cobalt(III) iodide have not been synthesized.

Structure

Anhydrous

Anhydrous cobalt trifluoride crystallizes in the rhombohedral group, specifically according to the aluminium trifluoride motif, with a = 527.9  pm and α = 56.97°. Each cobalt centre is bound to six fluorine atoms in octahedral geometry, with Co–F distances of 189 pm. Each fluoride is a doubly bridging ligand. [2]

Hydrates

A hydrate CoF3·3.5H2O is known, which is conjectured to be better described as [CoF3(H2O)3]·0.5H2O. [2]

There is a report of a hydrate CoF3·3.5H2O, isomorphic to AlF3·3H2O. [2]

Preparation

Cobalt trifluoride can be prepared in the laboratory by treating cobalt(II) chloride (CoCl2) with fluorine gas at 250 °C: [2] [5]

2 CoCl2 + 3 F2 → 2 CoF3 + 2 Cl2

In this redox reaction, the reduction of fluorine to fluoride ions drives the oxidation of both cobalt(II) cations and chloride anions to cobalt(III) ions and chlorine gas, respectively. Treatment of cobalt(II) chloride with chlorine trifluoride (ClF3) or bromine trifluoride (BrF3) also yield cobalt trifluoride, as does the direct fluoridation of cobalt(II) oxide or cobalt(II) fluoride: [2]

2 CoF2 + F2 → 2 CoF3

The other stable oxide of cobalt, cobalt(II,III) oxide (Co3O4), can be sequentially treated with hydrogen fluoride and then fluorine to produce first cobalt(II) fluoride and cobalt oxyfluoride and then cobalt(III) fluoride, with the overall stoichiometry: [6]

Co3O4 + 4 HF → CoF2 + 2 CoOF + 2 H2O
2CoF2 + 4 CoOF + 5 F2 → 6 CoF3 + 2 O2

This process reduces the need for expensive and difficult-to-handle fluorine gas. [6]

Reactions

CoF3 decomposes upon contact with water to give oxygen:

4 CoF3 + 2 H2O → 4 HF + 4 CoF2 + O2

It reacts with fluoride salts to give the hexafluorocobaltate(III) anion (CoF3−6), which features a high-spin, octahedral cobalt(III) center.

Applications

Synthesis of organofluorine compounds can be undertaken by direct reaction with fluorine, but this approach can result in fragmentation of the target hydrocarbon. [6] CoF3 is an alternative fluorinating agent that is still powerful, but milder than direct fluorination with fluorine. [6] [7] Used as slurry, CoF3 converts hydrocarbons to the perfluorocarbons: [7]

2 CoF3 + R-H → 2 CoF2 + R-F + HF

CoF2 is the byproduct.

A study of cobalt trifluoride fluorination of butane showed that a mixture of more than 51 polyfluorinated and perfluorinated butanes, as well as some substituted methylpropanes, were formed. [8] Fluorination of cyclopentane similarly yielded a mix of products with between five (C5H5F5) and ten fluorine substitutions (C5F10). [9] Formation of large numbers of products with low selectivity greatly limits the synthetic utility of cobalt trifluoride fluorination. [3] The related reagent potassium tetrafluorocobaltate(III) (KCoF4) is a more selective alternative. [10]

Gaseous CoF3

In the gas phase, CoF3 is calculated to be planar in its ground state, and has a 3-fold rotation axis (point group D3h). The Co3+ ion has a ground state of 3d65D. The fluoride ligands split this state into, in energy order, 5A', 5E", and 5E' states. The first energy difference is small and the 5E" state is subject to the Jahn-Teller effect, so this effect needs to be considered to be sure of the ground state. The energy lowering is small and does not change the energy order. [11] This calculation was the first treatment of the Jahn-Teller effect using calculated energy surfaces.

References

  1. ↑ PubChem. "Cobalt trifluoride". pubchem.ncbi.nlm.nih.gov. Retrieved 2026-03-12.
  2. 1 2 3 4 5 6 Levason, W.; McAuliffe, C. A. (1974). "Higher oxidation state chemistry of iron, cobalt, and nickel". Coordination Chemistry Reviews. 12 (2): 151–184. doi:10.1016/S0010-8545(00)82026-3.
  3. 1 2 Coe, P. L. (2004). "Cobalt(III) Fluoride". Encyclopedia of Reagents for Organic Synthesis. J. Wiley. doi:10.1002/047084289X.rc185. ISBN   0471936235.
  4. ↑ Chester, A. W.; Heiba, E.-A.; Dessau, R. M.; Koehl, Jr., W. J. (1969). "The interaction of cobalt(III) with chloride ion in acetic acid". Inorganic and Nuclear Chemistry Letters. 5 (4): 277–283. doi:10.1016/0020-1650(69)80198-4.
  5. ↑ Priest, H. F.; Swinehert, C. F. (1950). "Anhydrous Metal Fluorides". Inorganic Syntheses. 3. McGraw-Hill: 171–183. doi:10.1002/9780470132340.ch47.
  6. 1 2 3 4 Vilakazi, B. M.; Wagener, J. B.; van der Merwe, E. M. (2020). "A thermogravimetric investigation into the synthesis of CoF3 from Co3O4". Journal of Fluorine Chemistry. 240. doi:10.1016/j.jfluchem.2020.109638.
  7. 1 2 Sandford, G. (2003). "Perfluoroalkanes". Tetrahedron. 59 (4): 437–454. doi:10.1016/S0040-4020(02)01568-5.
  8. ↑ Burdon, J.; Ezmirly, S. T.; Huckerby, T. N. (1988). "The fluorination of Butane over cobalt trifluoride". Journal of Fluorine Chemistry. 40 (2–3): 283–318. doi:10.1016/S0022-1139(00)83070-5.
  9. ↑ Bergomi, A.; Burdon, J.; Hodgins, T. M.; Stephens, R.; Tatlow, J. C. (1966). "Fluorocyclopentanes—IV: The fluorination of cyclopentane with cobalt trifluoride". Tetrahedron. 22 (1): 43–51. doi:10.1016/0040-4020(66)80099-6.
  10. ↑ Coe, P. L. (2004). "Potassium Tetrafluorocobaltate(III)". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.rp251.
  11. ↑ Yates, J. H.; Pitzer, R. M. (1979). "Molecular and Electronic Structure of Transition Metal Trifluorides". J. Chem. Phys. 70 (9): 4049–4055. Bibcode:1979JChPh..70.4049Y. doi:10.1063/1.438027.
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