Chromyl fluoride

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Chromyl fluoride
Chromyl-fluoride-2D.svg
Names
IUPAC name
Difluoro(dioxo)chromium
Other names
Chromyl Fluoride, Chromium Difluoride Dioxide
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 232-137-9
PubChem CID
UNII
  • InChI=1S/Cr.2FH.2O/h;2*1H;;/q+2;;;;/p-2 X mark.svgN
    Key: FRLBLFFATGQISB-UHFFFAOYSA-L X mark.svgN
  • InChI=1/Cr.2FH.2O/h;2*1H;;/q+2;;;;/p-2/rCrF2O2/c2-1(3,4)5
    Key: FRLBLFFATGQISB-UNDMLHRZAG
  • O=[Cr](=O)(F)F
Properties
CrO2F2
Molar mass 121.991 g·mol−1
AppearanceViolet-red crystals
Melting point 31.6 °C (88.9 °F; 304.8 K)
Boiling point 30 °C (86 °F; 303 K) [1] Sublimes
Structure
monoclinic
P21/c, No. 14
C2v
4
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Oxidant
Related compounds
Related compounds
 chromyl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Chromyl fluoride is an inorganic compound with the formula CrO2F2. It is a violet-red colored crystalline solid that melts to an orange-red liquid. [2]

Contents

Structure

The liquid and gaseous CrO2F2 have a tetrahedral geometry with C2v symmetry, much like chromyl chloride. [3] Chromyl fluoride dimerizes via fluoride bridges (as O2Cr(μ-F)4CrO2) in the solid state, crystallizing in the P21/c space group with Z = 4. The Cr=O bond lengths are about 157  pm, and the Cr–F bond lengths are 181.7, 186.7, and 209.4 pm. Chromium resides in a distorted octahedral position with a coordination number of 6. [4]

History and preparation

Pure chromyl fluoride was first isolated in 1952 as reported by Alfred Engelbrecht and Aristid von Grosse. [5] It was first observed as red vapor in the early 19th century upon heating a mixture of fluorspar (CaF2), chromates, and sulfuric acid. These red vapors were initially thought to be CrF6, although some chemists assumed a CrO2F2 structure analogous to CrO2Cl2. [5] The first moderately successful synthesis of chromyl fluoride was reported by Fredenhagen who examined the reaction of hydrogen fluoride with alkali chromates. A later attempt saw von Wartenberg prepare impure CrO2F2 by treating chromyl chloride with elemental fluorine. [6] Another attempt was made by Wiechert, who treated HF with dichromate, yielding impure liquid CrO2F2 at −40 °C.

Engelbrecht and von Grosse's synthesis of CrO2F2, and most successive syntheses, involve treating chromium trioxide with a fluorinating agent: [5]

CrO3 + 2 HF → CrO2F2 + H2O

The reaction is reversible, as water will readily hydrolyze CrO2F2 back to CrO3.

The approach published by Georg Brauer in the Handbook of Preparative Inorganic Chemistry [1] drew on von Wartenberg's approach [6] of direct fluoridation:

CrO2Cl2 + F2 → CrO2F2 + Cl2

Other methods include treatment with chlorine fluoride, carbonyl fluoride, or some metal hexafluorides:

CrO3 + 2 ClF → CrO2F2 + Cl2 + O2
CrO3 + COF2 → CrO2F2 + CO2
CrO3 + MF6 → CrO2F2 + MOF4 (M = Mo, W)

The last method involving the fluorides of tungsten and molybdenum are reported by Green and Gard to be very simple and effective routes to large quantities of pure CrO2F2. [2] They reported 100% yield when the reactions were conducted at 120 °C. As expected from the relative reactivities of MoF6 and WF6, the molybdenum reaction proceeded more readily than did the tungsten. [7]

Reactions

Chromyl fluoride is a strong oxidizing agent capable of converting hydrocarbons to ketones and carboxylic acids. It can also be used as a reagent in the preparation of other chromyl compounds. [2] Like some other fluoride compounds, CrO2F2 reacts with glass and quartz, so silicon-free plastics or metal containers are required for handling the compound. Its oxidizing power in inorganic systems has also been explored. [8] Chromyl fluoride can exchange fluorine atoms with metal oxides.

CrO2F2 + MO → MF2 + CrO3

Chromyl fluoride will also convert the oxides of boron and silicon to the fluorides. [8]

Chromyl fluoride reacts with alkali and alkaline earth metal fluorides in perfluoroheptane (solvent) to produce orange-colored fluorochromates: [8]

CrO2F2 + 2 MF → M2[CrO2F4]

Chromyl fluoride also reacts with Lewis acids, drawing carboxylate ligands from organic acid anhydrides and producing an acyl fluoride byproduct: [8]

CrO2F2 + 2 (CF3CO)2O → (CF3COO)2CrO2 + 2 CF3COF

Chromyl fluoride forms adducts with weak bases NO, NO2, and SO2.

Related Research Articles

<span class="mw-page-title-main">Praseodymium(III) chloride</span> Chemical compound

Praseodymium(III) chloride is the inorganic compound with the formula PrCl3. Like other lanthanide trichlorides, it exists both in the anhydrous and hydrated forms. It is a blue-green solid that rapidly absorbs water on exposure to moist air to form a light green heptahydrate.

<span class="mw-page-title-main">Chromium(III) chloride</span> Chemical compound

Chromium(III) chloride (also called chromic chloride) describes any of several chemical compounds with the formula CrCl3 · xH2O, where x can be 0, 5, and 6. The anhydrous compound with the formula CrCl3 is a violet solid. The most common form of the trichloride is the dark green hexahydrate, CrCl3 · 6 H2O. Chromium chlorides find use as catalysts and as precursors to dyes for wool.

<span class="mw-page-title-main">Chromium(III) fluoride</span> Chemical compound

Chromium(III) fluoride is the name for the inorganic compounds with the chemical formula CrF3 as well as several related hydrates. The compound CrF3 is a green crystalline solid that is insoluble in common solvents, but the coloured hydrates [Cr(H2O)6]F3 and [Cr(H2O)6]F3•3H2O are soluble in water. The trihydrate is green, and the hexahydrate is violet. The anhydrous form sublimes at 1100–1200 °C.

<span class="mw-page-title-main">Cobalt(III) fluoride</span> Chemical compound

Cobalt(III) fluoride is the inorganic compound with the formula CoF3. Hydrates are also known. The anhydrous compound is a hygroscopic brown solid. It is used to synthesize organofluorine compounds.

<span class="mw-page-title-main">Chromium(II) chloride</span> Chemical compound

Chromium(II) chloride describes inorganic compounds with the formula CrCl2(H2O)n. The anhydrous solid is white when pure, however commercial samples are often grey or green; it is hygroscopic and readily dissolves in water to give bright blue air-sensitive solutions of the tetrahydrate Cr(H2O)4Cl2. Chromium(II) chloride has no commercial uses but is used on a laboratory-scale for the synthesis of other chromium complexes.

<span class="mw-page-title-main">Chromyl chloride</span> Chemical compound

Chromyl chloride is an inorganic compound with the formula CrO2Cl2. It is a reddish brown compound that is a volatile liquid at room temperature, which is unusual for transition metal compounds.

<span class="mw-page-title-main">Zinc fluoride</span> Chemical compound

Zinc fluoride is an inorganic chemical compound with the chemical formula ZnF2. It is encountered as the anhydrous form and also as the tetrahydrate, ZnF2·4H2O (rhombohedral crystal structure). It has a high melting point and has the rutile structure containing 6 coordinate zinc, which suggests appreciable ionic character in its chemical bonding. Unlike the other zinc halides, ZnCl2, ZnBr2 and ZnI2, it is not very soluble in water.

<span class="mw-page-title-main">Selenium tetrafluoride</span> Chemical compound

Selenium tetrafluoride (SeF4) is an inorganic compound. It is a colourless liquid that reacts readily with water. It can be used as a fluorinating reagent in organic syntheses (fluorination of alcohols, carboxylic acids or carbonyl compounds) and has advantages over sulfur tetrafluoride in that milder conditions can be employed and it is a liquid rather than a gas.

<span class="mw-page-title-main">Chromium compounds</span> Chemical compounds containing chromium

Chromium is a member of group 6, of the transition metals. The +3 and +6 states occur most commonly within chromium compounds, followed by +2; charges of +1, +4 and +5 for chromium are rare, but do nevertheless occasionally exist.

Antimony trifluoride is the inorganic compound with the formula SbF3. Sometimes called Swarts' reagent, is one of two principal fluorides of antimony, the other being SbF5. It appears as a white solid. As well as some industrial applications, it is used as a reagent in inorganic and organofluorine chemistry.

<span class="mw-page-title-main">Sulfuryl chloride fluoride</span> Chemical compound

Sulfuryl chloride fluoride is a chemical compound with the formula SO2ClF. It is a colorless, easily condensed gas. It is a tetrahedral molecule.

<span class="mw-page-title-main">Manganese(IV) fluoride</span> Chemical compound

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.

<span class="mw-page-title-main">Potassium chlorochromate</span> Chemical compound

Potassium chlorochromate is an inorganic compound with the formula KCrO3Cl. It is the potassium salt of chlorochromate, [CrO3Cl]−. It is a water-soluble orange compound is used occasionally for oxidation of organic compounds. It is sometimes called Péligot's salt, in recognition of its discoverer Eugène-Melchior Péligot.

<span class="mw-page-title-main">Sulfur chloride pentafluoride</span> Chemical compound

Sulfur chloride pentafluoride is an inorganic compound with the formula SF5Cl. It exists as a colorless gas at room temperature and is highly toxic, like most inorganic compounds containing the pentafluorosulfide functional group. The compound adopts an octahedral geometry with C
4v symmetry. Sulfur chloride pentafluoride is the only commercially available reagent for adding the –SF5 group to organic compounds.

In chemistry, molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula AOmXn, where X is a halogen. Known oxohalides have fluorine (F), chlorine (Cl), bromine (Br), and/or iodine (I) in their molecules. The element A may be a main group element, a transition element, a rare earth element or an actinide. The term oxohalide, or oxyhalide, may also refer to minerals and other crystalline substances with the same overall chemical formula, but having an ionic structure.

<span class="mw-page-title-main">Chromium(II) fluoride</span> Chemical compound

Chromium(II) fluoride is an inorganic compound with the formula CrF2. It exists as a blue-green iridescent solid. Chromium(II) fluoride is sparingly soluble in water, almost insoluble in alcohol, and is soluble in boiling hydrochloric acid, but is not attacked by hot distilled sulfuric acid or nitric acid. Like other chromous compounds, chromium(II) fluoride is oxidized to chromium(III) oxide in air.

Chromium pentafluoride is the inorganic compound with the chemical formula CrF5. It is a red volatile solid that melts at 34 °C. It is the highest known chromium fluoride, since the hypothetical chromium hexafluoride has not yet been synthesized.

<span class="mw-page-title-main">Difluorophosphate</span> Chemical compound

Difluorophosphate or difluorodioxophosphate or phosphorodifluoridate is an anion with formula PO2F−2. It has a single negative charge and resembles perchlorate and monofluorosulfonate in shape and compounds. These ions are isoelectronic, along with tetrafluoroaluminate, phosphate, orthosilicate, and sulfate. It forms a series of compounds. The ion is toxic to mammals as it causes blockage to iodine uptake in the thyroid. However it is degraded in the body over several hours.

<span class="mw-page-title-main">Hexafluoroarsenate</span> Chemical compound

The hexafluoroarsenate anion is a chemical species with formula AsF−6. Hexafluoroarsenate is relatively inert, being the conjugate base of the notional superacid hexafluoroarsenic acid.

References

  1. 1 2 Brauer, Georg (1963) [1960]. "Chromyl Fluoride –CrO
    2    F
    2    "    . Handbook of Preparative Inorganic Chemistry, Volume 1 (2nd ed.). Stuttgart; New York: Ferdinand Enke Verlag; Academic Press, Inc. pp. 258–259. ISBN   978-0-32316127-5.
  2. 1 2 3 Gard, G. L. (1986) "Chromium Difluoride Dioxide (Chromyl Fluoride)," Inorg. Synth. , 24, 67-69, doi : 10.1002/9780470132555.ch20.
  3. ↑ Hobbs, W. E. (1958) "Infrared Absorption Spectra of Chromyl Fluoride and Chromyl Chloride," J. Chem. Phys. 28(6), 1220-1222, doi : 10.1063/1.1744372.
  4. ↑ Supeł, J.; Abram, U.; Hagenbach, A.; Seppelt, K. (2007) "Technetium Fluoride Trioxide, TcO3F, Preparation and Properties." Inorg. Chem. , 46(14), 5591–5595, doi : 10.1021/ic070333y.
  5. 1 2 3 Engelbrecht, A.; von Grosse, A. (1952) "Pure Chromyl Fluoride," J. Am. Chem. Soc. 74(21), 5262–5264, doi : 10.1021/ja01141a007.
  6. 1 2 von Wartenberg, H. (1941) "Über höhere Chromfluoride (CrF
    4    , CrF
    5     und CrO
    2    F
    2    )" [About higher chromium fluorides (CrF
    4    , CrF
    5     and CrO
    2    F
    2    )], Z. Anorg. Allg. Chem. [in German], 247(1-2), 135–146, doi : 10.1002/zaac.19412470112.
  7. ↑ Green, P. J.; Gard, G. L. (1977) "Chemistry of Chromyl Fluoride. 5. New Preparative routes to CrO2F2," Inorg. Chem. 16(5), 1243–1245, doi : 10.1021/ic50171a055.
  8. 1 2 3 4 Brown, S. D.; Green, P.J.; Gard, G.L. (1975) "The Chemistry of Chromyl Fluoride III: Reactions with Inorganic Systems," J. Fluorine Chem. 5(3), 203-219, doi : 10.1016/S0022-1139(00)82482-3.
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