Dichlorine hexoxide
Space-filling model of the dichlorine hexoxide molecule
Space-filling model of the component ions of dichlorine hexoxide
Names
IUPAC name
Dichlorine hexoxide
Other names
Chlorine trioxide; Chloryl perchlorate; Chlorine(V,VII) oxide
Identifiers
3D model (JSmol)
ChemSpider
  • InChI=1S/Cl2O6/c3-1(4)8-2(5,6)7
    Key: BMVIIZAOKBSWDS-UHFFFAOYSA-N
  • O=[Cl](=O)O[Cl](=O)(=O)=O
  • O=[Cl+]=O.[O-]Cl(=O)(=O)=O
Properties
Cl2O6
Molar mass 166.901 g/mol
Appearance red liquid
Density 1.65 g/cm3
Melting point 3.5 °C (38.3 °F; 276.6 K)
Boiling point 200 °C (392 °F; 473 K)
Reacts
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
oxidizer
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Dichlorine hexoxide is the chemical compound with the molecular formula Cl
2
O
6
, 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 [ClO
2
]+
[ClO
4
]
, which may be thought of as the mixed anhydride of chloric and perchloric acids.

It is produced by reaction between chlorine dioxide and excess ozone:

2 ClO
2
+ 2 O
3
→ 2 ClO
3
+ 2 O
2
Cl
2
O
6
+ 2 O
2

Molecular structure

It was originally reported to exist as the monomeric chlorine trioxide ClO3 in gas phase,[1] but was later shown to remain an oxygen-bridged dimer after evaporation and until thermal decomposition into chlorine perchlorate, Cl2O4, and oxygen.[2] The compound ClO3 was then rediscovered.[3]

It is a dark red fuming liquid at room temperature that crystallizes as a red ionic compound, chloryl perchlorate, [ClO
2
]+
[ClO
4
]
. 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

Cl2O6 is diamagnetic and is a very strong oxidizing agent. Although stable at room temperature, it explodes violently on contact with organic compounds[4] and reacts with gold to produce the chloryl salt [ClO
2
]+
[Au(ClO
4
)
4
]
.[5] Many other reactions involving Cl2O6 reflect its ionic structure, [ClO
2
]+
[ClO
4
]
, including the following:[6]

NO2F + Cl2O6 → NO2ClO4 + ClO2F
NO + Cl2O6 → NOClO4 + ClO2
2 V2O5 + 12 Cl2O6 → 4 VO(ClO4)3 + 12 ClO2 + 3 O2
SnCl4 + 6 Cl2O6 → [ClO2]2[Sn(ClO4)6] + 4 ClO2 + 2 Cl2
2Au + 6Cl2O6 2[ClO
2
]+
[Au(ClO
4
)
4
]
+ Cl2

Nevertheless, it can also react as a source of the ClO3 radical:

2 AsF5 + Cl2O6 → 2 ClO3AsF5

References

  1. C. F. Goodeve, F. A. Todd (1933). "Chlorine Hexoxide and Chlorine Trioxide". Nature. 132 (3335): 514–515. Bibcode:1933Natur.132..514G. doi:10.1038/132514b0. S2CID 4116929.
  2. Lopez, Maria; Juan E. Sicre (1990). "Physicochemical properties of chlorine oxides. 1. Composition, ultraviolet spectrum, and kinetics of the thermolysis of gaseous dichlorine hexoxide". J. Phys. Chem. 94 (9): 3860–3863. doi:10.1021/j100372a094.
  3. Grothe, Hinrich; Willner, Helge (1994). "Chlorine Trioxide: Spectroscopic Properties, Molecular Structure, and Photochemical Behavior". Angew. Chem. Int. Ed. 33 (14): 1482–1484. doi:10.1002/anie.199414821.
  4. Mary Eagleson (1994). Concise encyclopedia chemistry. Walter de Gruyter. p. 215. ISBN 3-11-011451-8.
  5. Cunin, Frédérique; Catherine Deudon; Frédéric Favier; Bernard Mula; Jean Louis Pascal (2002). "First anhydrous gold perchlorato complex: ClO
    2
    Au(ClO
    4
    )
    4
    . Synthesis and molecular and crystal structure analysis". Inorganic Chemistry. 41 (16): 4173–4178. doi:10.1021/ic020161z. PMID 12160405.
  6. Harry Julius Emeléus, Alan George Sharpe (1963). Advances in Inorganic Chemistry and Radiochemistry. Academic Press. p. 65. ISBN 0-12-023605-2.
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