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{{Chembox |
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| verifiedrevid = 426430565 |
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| verifiedrevid = 444147645 |
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| ImageFile = |
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| Name = |
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| ImageFile = Chromyl-fluoride-2D.svg |
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| OtherNames = Chromyl Fluoride, Chromium Difluoride Dioxide |
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| ImageSize = 200px |
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| IUPACName = Difluoro(dioxo)chromium |
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| OtherNames = Chromyl Fluoride, Chromium Difluoride Dioxide |
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| SystematicName = |
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| Section1 = {{Chembox Identifiers |
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| Section1 = {{Chembox Identifiers |
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| CASNo_Ref = {{cascite|correct|??}} |
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| CASNo = 7788-96-7 |
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| PubChem = |
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| CASNo = 7788-96-7 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| SMILES = }} |
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| UNII = UB519P5O68 |
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| EINECS = 232-137-9 |
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| PubChem = 53471881 |
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| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}} |
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| ChemSpiderID = 10329781 |
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| SMILES = O=(=O)(F)F |
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| InChI = 1/Cr.2FH.2O/h;2*1H;;/q+2;;;;/p-2/rCrF2O2/c2-1(3,4)5 |
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| InChIKey = FRLBLFFATGQISB-UNDMLHRZAG |
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| StdInChI_Ref = {{stdinchicite|changed|chemspider}} |
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| StdInChI = 1S/Cr.2FH.2O/h;2*1H;;/q+2;;;;/p-2 |
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| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}} |
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| StdInChIKey = FRLBLFFATGQISB-UHFFFAOYSA-L }} |
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| Section2 = {{Chembox Properties |
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| Section2 = {{Chembox Properties |
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| Formula = CrO<sub>2</sub>F<sub>2</sub> |
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| Formula = {{chem2|CrO2F2}} |
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| Cr=1|O=2|F=2 |
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| MolarMass = 112 g/mol |
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| Appearance = violet crystals |
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| Appearance = Violet-red crystals |
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| Density = |
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| Density = |
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| MeltingPt = 31.6°C |
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| MeltingPtC = 31.6 |
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| BoilingPt = |
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| BoilingPtC = 30 |
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| BoilingPt_ref = <ref name = Brauer>{{cite book|last = Brauer|first = Georg|author-link = Georg Brauer|year = 1963|orig-year = 1960|title = Handbook of Preparative Inorganic Chemistry, Volume 1|chapter = Chromyl Fluoride – {{chem|CrO|2|F|2}}|chapter-url = https://books.google.com/books?id=kaa2qeFRXmUC&pg=PA258|location = Stuttgart; New York|publisher = ]; ]|pages = 258–259|isbn = 978-0-32316127-5|edition = 2nd}}</ref> |
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| Solubility = }} |
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| BoilingPt_notes = Sublimes |
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| Section3 = {{Chembox Hazards |
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| MainHazards = Oxidant |
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| Solubility = }} |
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| Section3 = {{Chembox Structure |
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| FlashPt = |
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| CrystalStruct = monoclinic |
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| SpaceGroup = P2<sub>1</sub>/c, No. 14 |
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| PointGroup = C<sub>2v</sub> |
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| UnitCellFormulas = 4 |
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'''Chromyl fluoride''' is an ] with the formula CrO<sub>2</sub>F<sub>2</sub>. It is a violet-red colored crystalline solid that melts to an orange-red liquid.<ref name=Gard>Gard, G. L. "Chromium Difluoride Dioxide (Chromyl Fluoride)" Inorganic Syntheses 1986, Volume 24, p67.</ref> |
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| MainHazards = Oxidant |
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| FlashPt = |
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| AutoignitionPt = }} |
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| Section5 = {{Chembox Related |
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| OtherCompounds = ] |
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'''Chromyl fluoride''' is an ] with the formula {{chem2|CrO2F2}}. It is a violet-red colored crystalline solid that melts to an orange-red liquid.<ref name=Gard>Gard, G. L. (1986) "Chromium Difluoride Dioxide (Chromyl Fluoride)," '']'', '''24''', 67-69, {{doi|10.1002/9780470132555.ch20}}.</ref> |
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==Structure== |
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==Structure== |
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The liquid and gaseous CrO<sub>2</sub>F<sub>2</sub> have a tetrahedral geometry with C<sub>2V</sub> ], much like ].<ref>Hobbs, W. E. "Infrared Absorption Spectra of Chromyl Fluoride and Chromyl Chloride" J. Chem. Phys. 28, 1220. {{DOI|10.1063/1.1744372}}</ref> Chromyl fluoride crystallizes in the P2<sub>1/c</sub> ] with Z=4. The Cr=O bond lengths are about 157 ], 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.<ref>Supel, J., Abram, U., Hagenbach, A., Seppelt, K., Technetium Fluoride Trioxide, TcO3F, Preparation and Properties Inorg. Chem., 2007, 46 (14), 5591–5595. {{DOI|10.1021/ic070333y}}</ref> It dimerizes via fluoride bridges in the solid state. |
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The liquid and gaseous {{chem2|CrO2F2}} have a tetrahedral geometry with C<sub>2v</sub> ], much like ].<ref>Hobbs, W. E. (1958) "Infrared Absorption Spectra of Chromyl Fluoride and Chromyl Chloride," '']'' '''28'''(''6''), 1220-1222, {{doi|10.1063/1.1744372}}.</ref> Chromyl fluoride ] via fluoride bridges (as {{chem2|O2Cr(''μ''\-F)4CrO2}}) in the solid state, crystallizing in the P2<sub>1</sub>/c ] with Z = 4. The Cr=O bond lengths are about 157 ], 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.<ref>Supeł, J.; Abram, U.; Hagenbach, A.; ] (2007) "Technetium Fluoride Trioxide, TcO<sub>3</sub>F, Preparation and Properties." '']'', '''46'''(''14''), 5591–5595, {{doi|10.1021/ic070333y}}.</ref> |
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==Reactions== |
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Chromyl fluoride is a strong ] capable of converting hydrocarbons to ketones and carboxylic acids. It can also be used as a reagent in the preparation of other chromyl compounds.<ref name=Gard/> Like some other fluoride compounds, CrO<sub>2</sub>F<sub>2</sub> reacts with glass and quartz, so silicon-free plastics or metals must be used when handling the compound. |
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==History and preparation== |
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==History and preparation== |
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Pure chromyl fluoride was first isolated in 1952 as reported by Engelbrecht and Grosse.<ref name=Engel>Engelbrecht, A., Grosse, A. V. Pure Chromyl Fluoride. J. Am. Chem. Soc. 74, 5262.</ref> It was first observed as red vapor in the early 19th century upon heating a mixture of fluorspar (CaF<sub>2</sub>), chromates, and sulfuric acid. These red vapors were initially thought to be CrF<sub>6</sub>, although some chemists assumed a CrO<sub>2</sub>F<sub>2</sub> structure analogous to CrO<sub>2</sub>Cl<sub>2</sub>.<ref name=Engel/> The first moderately successful synthesis of chromyl fluoride was reported by Fredenhagen who examined the reaction of ] with alkali chromates. A later attempt saw Wartenberg prepared impure CrO<sub>2</sub>F<sub>2</sub> by treating CrO<sub>2</sub>Cl<sub>2</sub> with elemental ]. Another attempt was made by Wiechert, who treated HF with dichromate, yielding impure liquid CrO2F2 at -40 °C. |
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Pure chromyl fluoride was first isolated in 1952 as reported by Alfred Engelbrecht and ].<ref name = Engel>Engelbrecht, A.; ] (1952) "Pure Chromyl Fluoride," '']'' '''74'''(''21''), 5262–5264, {{doi|10.1021/ja01141a007}}.</ref> It was first observed as red vapor in the early 19th century upon heating a mixture of ] ({{chem2|CaF2}}), chromates, and ]. These red vapors were initially thought to be {{chem2|CrF6}}, although some chemists assumed a {{chem2|CrO2F2}} structure analogous to {{chem2|CrO2Cl2}}.<ref name = Engel /> The first moderately successful synthesis of chromyl fluoride was reported by Fredenhagen who examined the reaction of ] with alkali chromates. A later attempt saw von Wartenberg prepare impure {{chem2|CrO2F2}} by treating ] with elemental ].<ref name = vonW>von Wartenberg, H. (1941) "Über höhere Chromfluoride ({{chem|CrF|4}}, {{chem|CrF|5}} und {{chem|CrO|2|F|2}})" , '']'' , '''247'''(''1-2''), 135–146, {{doi|10.1002/zaac.19412470112}}.</ref> Another attempt was made by Wiechert, who treated HF with dichromate, yielding impure liquid {{chem2|CrO2F2}} at −40 °C. |
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Engelbrecht and von Grosse's synthesis of {{chem2|CrO2F2}}, and most successive syntheses, involve treating ] with a fluorinating agent:<ref name = Engel /> |
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:{{chem2|CrO3 + 2 HF → CrO2F2 + H2O}} |
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The reaction is reversible, as water will readily hydrolyze {{chem2|CrO2F2}} back to {{chem2|CrO3}}. |
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The approach published by ] in the ''Handbook of Preparative Inorganic Chemistry''<ref name = Brauer /> drew on von Wartenberg's approach<ref name = vonW /> of direct fluoridation: |
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:{{chem2|CrO2Cl2 + F2 → CrO2F2 + Cl2}} |
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Engelbrecht and Grosse’s synthesis of CrO<sub>2</sub>F<sub>2</sub>, and most successive syntheses, involve treating ] (CrO<sub>3</sub>) with a fluorinating agent: |
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:CrO<sub>3</sub> + 2 HF → CrO<sub>2</sub>F<sub>2</sub> + H<sub>2</sub>O |
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The reaction is reversible, as water will readily hydrolyze CrO<sub>2</sub>F<sub>2</sub> back to CrO<sub>3</sub>. |
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Other methods include treatment with ], ], or some metal hexafluorides: |
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Other methods include treatment with ], ], or some metal hexafluorides: |
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:{{chem2|CrO3 + 2 ClF → CrO2F2 + Cl2 + O2}} |
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:CrO<sub>3</sub> + 2 ClF → CrO<sub>2</sub>F<sub>2</sub> + Cl<sub>2</sub> + O<sub>2</sub> |
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:{{chem2|CrO3 + COF2 → CrO2F2 + CO2}} |
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:CrO<sub>3</sub> + COF<sub>2</sub> → CrO<sub>2</sub>F<sub>2</sub> + CO<sub>2</sub> |
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:CrO<sub>3</sub> + MF<sub>6</sub> → CrO<sub>2</sub>F<sub>2</sub> + MOF<sub>4</sub> (M = Mo, W) |
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:{{chem2|CrO3 + MF6 → CrO2F2 + MOF4}} (M = Mo, W) |
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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 CrO<sub>2</sub>F<sub>2</sub>.<ref name=Gard/> They reported 100% yield when the reactions were conducted at 120°C. As expected from the relative reactivities of MoF<sub>6</sub> and WF<sub>6</sub>, the MoF<sub>6</sub> reaction proceeded more readily.<ref>Green, P.J., Gard, G.L., Chemistry of Chromyl Fluoride. New Preparative routes to CrO<sub>2</sub>F<sub>2</sub>. Inorg. Chem. 16, 1243. {{DOI|10.1021/ic50171a055}}</ref> |
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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 {{chem2|CrO2F2}}.<ref name=Gard/> They reported 100% yield when the reactions were conducted at 120 °C. As expected from the relative reactivities of {{chem2|MoF6}} and {{chem2|WF6}}, the molybdenum reaction proceeded more readily than did the tungsten.<ref>Green, P. J.; Gard, G. L. (1977) "Chemistry of Chromyl Fluoride. 5. New Preparative routes to CrO<sub>2</sub>F<sub>2</sub>," '']'' '''16'''(''5''), 1243–1245, {{doi|10.1021/ic50171a055}}.</ref> |
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==Reactions== |
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==Reactions== |
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In addition to being to oxidizing hydrocarbons to ketones and carboxylic acids, CrO<sub>2</sub>F<sub>2</sub> participates in a variety of other reactions as reported by Brown, Green, and Gard.<ref>Brown, S. D., Green, P.J., Gard, G.L., The Chemistry of Chromyl Fluoride, III: Reactions with Inorganic Systems. J. Fluorine Chem. 5, 203 {{DOI|10.1016/S0022-1139(00)82482-3}}</ref> Chromyl Fluoride can exchange fluorine atoms with metal oxides. |
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Chromyl fluoride is a strong ] capable of converting hydrocarbons to ketones and carboxylic acids. It can also be used as a reagent in the preparation of other chromyl compounds.<ref name=Gard/> Like some other fluoride compounds, {{chem2|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.<ref name = Brown>Brown, S. D.; Green, P.J.; Gard, G.L. (1975) "The Chemistry of Chromyl Fluoride III: Reactions with Inorganic Systems," '']'' '''5'''(''3''), 203-219, {{doi|10.1016/S0022-1139(00)82482-3}}.</ref> Chromyl fluoride can exchange fluorine atoms with metal oxides. |
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:{{chem2|CrO2F2 + MO → MF2 + CrO3}} |
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:CrO<sub>2</sub>F<sub>2</sub> + MO → MF<sub>2</sub> + CrO<sub>3</sub> |
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Chromyl fluoride will also convert the oxides of boron and silicon to the fluorides. |
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Chromyl fluoride will also convert the oxides of boron and silicon to the fluorides.<ref name = Brown /> |
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Chromyl fluoride reacts with alkali and alkaline earth metal fluorides in a perfluoroheptane solvent to produce the orange-colored fluorochromates: |
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Chromyl fluoride reacts with alkali and alkaline earth metal fluorides in ] (solvent) to produce orange-colored fluorochromates:<ref name = Brown /> |
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:{{chem2|CrO2F2 + 2 MF → M2}} |
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:CrO<sub>2</sub>F<sub>2</sub> + 2 MF → M<sub>2</sub>CrO<sub>2</sub>F<sub>4</sub> |
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Chromyl fluoride also reacts with ]s, drawing carboxylate ligands from ]s and producing an ] byproduct:<ref name = Brown /> |
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Chromyl fluoride will react with Lewis acids as well: |
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:{{chem2|CrO2F2 + 2 (CF3CO)2O → (CF3COO)2CrO2 + 2 CF3COF}} |
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:CrO<sub>2</sub>F<sub>2</sub> + 2(CF<sub>3</sub>CO)<sub>2</sub>O → CrO<sub>2</sub>(CF<sub>3</sub>COO)<sub>2</sub> + 2CF<sub>3</sub>COF |
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Chromyl fluoride forms adducts with weak bases NO, NO2, and SO<sub>2</sub>. |
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Chromyl fluoride forms adducts with weak bases NO, {{chem2|NO2}}, and {{chem2|SO2}}. |
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] is prepared by fluorination of chromyl fluoride with ]:<ref>{{cite journal |doi=10.1021/ic00233a013 |title=Synthesis and characterization of CrF4O, KrF2.CrF4O, and NO+CrF5O- |date=1986 |last1=Christe |first1=Karl O. |last2=Wilson |first2=William W. |last3=Bougon |first3=Roland A. |journal=Inorganic Chemistry |volume=25 |issue=13 |pages=2163–2169 }}</ref> |
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:{{chem2|CrO2F2 + KrF2 -> CrOF4 + 0.5 O2 + Kr}} |
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==References== |
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==References== |
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<references/> |
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{{Chromium compounds}} |
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