Loading AI tools
Chemical compound From Wikipedia, the free encyclopedia
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]
Names | |
---|---|
IUPAC name
Difluoro(dioxo)chromium | |
Other names
Chromyl Fluoride, Chromium Difluoride Dioxide | |
Identifiers | |
3D model (JSmol) |
|
ChemSpider | |
EC Number |
|
PubChem CID |
|
UNII | |
| |
| |
Properties | |
CrO2F2 | |
Molar mass | 121.991 g·mol−1 |
Appearance | Violet-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 | |
Formula units (Z) |
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).
|
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]
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]
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:
Other methods include treatment with chlorine fluoride, carbonyl fluoride, or some metal hexafluorides:
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]
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.
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]
Chromyl fluoride also reacts with Lewis acids, drawing carboxylate ligands from organic acid anhydrides and producing an acyl fluoride byproduct:[8]
Chromyl fluoride forms adducts with weak bases NO, NO2, and SO2.
Chromium oxytetrafluoride is prepared by fluorination of chromyl fluoride with krypton difluoride:[9]
Seamless Wikipedia browsing. On steroids.
Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.
Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.