Dichlorine hexoxide
{{chembox
| Watchedfields = changed
| verifiedrevid = 440332808
| ImageFile = Dichlorine hexoxide.svg
| ImageClass = skin-invert-image
| ImageSize = 260
| ImageFileL1 = Dichlorine-hexoxide molecule spacefill.png
| ImageClassL1 = bg-transparent
| ImageSizeL1 = 105
| ImageAltL1 = Space-filling model of the dichlorine hexoxide molecule
| ImageFileR1 = Dichlorine-hexoxide ions spacefill.png
| ImageClassR1 = bg-transparent
| ImageSizeR1 = 135
| ImageAltR1 = Space-filling model of the component ions of dichlorine hexoxide
| ImageFile2 = Dichlorine hexoxide.png
| IUPACName = Dichlorine hexoxide
| OtherNames = Chlorine trioxide; Chloryl perchlorate; Chlorine(V,VII) oxide
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 12442-63-6
| PubChem = 101946322
| PubChem_Comment =
| ChemSpiderID = 9564507
| ChemSpiderID_Comment = incorrect charge
| SMILES = O=[Cl](=O)O[Cl](=O)(=O)=O
| SMILES1 = O=[Cl+]=O.[O-]Cl(=O)(=O)=O
| InChI=1S/Cl2O6/c3-1(4)8-2(5,6)7
| InChIKey = BMVIIZAOKBSWDS-UHFFFAOYSA-N
}}
|Section2={{Chembox Properties
| Formula = {{chem2|Cl2O6}}
| MolarMass = 166.901 g/mol
| Appearance = red liquid
| Density = 1.65 g/cm3
| MeltingPtC = 3.5
| BoilingPtC = 200
| Solubility = Reacts
}}
|Section3={{Chembox Hazards
| MainHazards = oxidizer
| FlashPt =
| AutoignitionPt =
}}
}}
Dichlorine hexoxide is the chemical compound with the molecular formula {{chem2|Cl2O6}} or {{chem2|O2Cl\sO\sClO3}}, which is correct for its gaseous state. However, in liquid or solid form, this chlorine oxide ionizes into the dark red ionic compound chloryl perchlorate or dioxochloronium(V) perchlorate {{chem2|[ClO2]+[ClO4]-}}, which may be thought of as the mixed anhydride of chloric and perchloric acids. This compound is a notable perchlorating agent.{{cite journal |author1=Jean-Louis Pascal |author2=Frédéric Favier |title=Inorganic perchlorato complexes |journal=Coordination Chemistry Reviews |date=1998 |volume=178-180 |issue=1 |pages=865–902 |doi=10.1016/S0010-8545(98)00102-7 |language=en}}
Molecular structure
It was originally reported to exist as the monomeric chlorine trioxide {{chem2|ClO3}} in gas phase,{{cite journal|journal=Nature|title=Chlorine Hexoxide and Chlorine Trioxide|volume=132|pages=514–515|year=1933|doi=10.1038/132514b0|author=C. F. Goodeve, F. A. Todd|issue=3335|bibcode=1933Natur.132..514G |s2cid=4116929}} but was later shown to remain an oxygen-bridged dimer after evaporation and until thermal decomposition into chlorine perchlorate, {{chem2|Cl2O4}}, and oxygen.{{cite journal|first=Maria|last=Lopez|author2=Juan E. Sicre|title=Physicochemical properties of chlorine oxides. 1. Composition, ultraviolet spectrum, and kinetics of the thermolysis of gaseous dichlorine hexoxide|journal=J. Phys. Chem.|year=1990|volume=94|issue=9|pages=3860–3863|doi=10.1021/j100372a094}} The compound {{chem2|ClO3}} was then rediscovered.{{cite journal|first1=Hinrich|last1=Grothe|first2=Helge|last2=Willner|title=Chlorine Trioxide: Spectroscopic Properties, Molecular Structure, and Photochemical Behavior|journal=Angew. Chem. Int. Ed.|year=1994|volume=33|issue=14|pages=1482–1484|doi=10.1002/anie.199414821}}
It is a dark red fuming liquid at room temperature that crystallizes as a red ionic compound, chloryl perchlorate, {{chem2|[ClO2]+[ClO4]-}}. The red color shows the presence of chloryl ions. Thus, chlorine's formal oxidation state in this compound remains a mixture of chlorine(V) and chlorine(VII) both in the gas phase and when condensed; however by breaking one oxygen-chlorine bond some electron density does shifts towards the chlorine(VII).
Properties
{{chem2|Cl2O6}} is diamagnetic and is a very strong oxidizing agent. Although stable at room temperature, it explodes violently on contact with organic compounds{{cite book|title=Concise encyclopedia chemistry|author=Mary Eagleson|url=https://archive.org/details/conciseencyclope00eagl|url-access=registration|isbn=3-11-011451-8|year=1994|publisher=Walter de Gruyter|page=[https://archive.org/details/conciseencyclope00eagl/page/215 215]}} It is a strong dehydrating agent:
:{{chem2|Cl2O6 + H2O → HClO4 + HClO3}}
Many reactions involving {{chem2|Cl2O6}} reflect its ionic structure, {{chem2|[ClO2]+[ClO4]-}}, including the following:{{cite book|page=65|url=https://books.google.com/books?id=pRXIwIV-hB8C|title=Advances in Inorganic Chemistry and Radiochemistry|isbn=0-12-023605-2|publisher=Academic Press|year=1963|author= Harry Julius Emeléus, Alan George Sharpe}}
:{{chem2|NO2F + Cl2O6 → [NO2]+ClO4- + ClO2F}}
:{{chem2|NO + Cl2O6 → [NO]+ClO4- + ClO2}}
:{{chem2|2 V2O5 + 12 Cl2O6 → 4 VO(ClO4)3 + 12 ClO2 + 3 O2}}
:{{chem2|SnCl4 + 6 Cl2O6 → [ClO2]2[Sn(ClO4)6] + 4 ClO2 + 2 Cl2}}
It reacts with gold to produce the chloryl salt chloryl tetraperchloratoaurate:{{cite journal|first=Frédérique|last=Cunin|author2=Catherine Deudon |author3=Frédéric Favier |author4=Bernard Mula |author5=Jean Louis Pascal |title=First Anhydrous Gold Perchlorato Complex: ClO2Au(ClO4)4. Synthesis and Molecular and Crystal Structure Analysis|journal=Inorganic Chemistry|volume=41|issue=16|year=2002|pages=4173–4178|doi=10.1021/ic020161z|pmid=12160405}}
:{{chem2|2 Au + 6 Cl2O6 → 2 [ClO2]+[Au(ClO4)4]- + Cl2}}
Several other transition metal perchlorate complexes are prepared using dichlorine hexoxide.
Nevertheless, it can also react as a source of the {{chem2|ClO3}} radical:{{cn|date=August 2024}}
:{{chem2|2 AsF5 + Cl2O6 → 2 ClO3AsF5}}
Synthesis
:{{chem2|4 ClO2 + 2 O3 → 2 Cl2O6 + O2}} (under ultraviolet light)