Chromyl fluoride
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| Names | |
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IUPAC name
Difluoro(dioxo)chromium
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| Other names
Chromyl Fluoride, Chromium Difluoride Dioxide
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3D model (Jmol)
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| ChemSpider | |
| EC Number | 232-137-9 |
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| Properties | |
| CrO2F2 | |
| Molar mass | 112 g/mol |
| Appearance | violet crystals |
| Melting point | 31.6 °C (88.9 °F; 304.8 K) |
| Boiling point | 30 °C (86 °F; 303 K) Sublimes |
| Hazards | |
| Main hazards | Oxidant |
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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.
The liquid and gaseous CrO2F2 have a tetrahedral geometry with C2Vsymmetry, much like chromyl chloride. Chromyl fluoride crystallizes in the P21/cspace 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 209.4pm. Chromium resides in a distorted octahedral position with a coordination number of six. It dimerizes via fluoride bridges in the solid state.
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. Like some other fluoride compounds, CrO2F2 reacts with glass and quartz, so silicon-free plastics or metals must be used when handling the compound.
Pure chromyl fluoride was first isolated in 1952 as reported by Engelbrecht and Grosse. 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. 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 Wartenberg prepared impure CrO2F2 by treating CrO2Cl2 with elemental fluorine. Another attempt was made by Wiechert, who treated HF with dichromate, yielding impure liquid CrO2F2 at -40 °C.
Engelbrecht and Grosse’s synthesis of CrO2F2, and most successive syntheses, involve treating chromium trioxide (CrO3) with a fluorinating agent:
The reaction is reversible, as water will readily hydrolyze CrO2F2 back to CrO3. Other methods include treatment with chlorine fluoride, carbonyl fluoride, or some metal hexafluorides:
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