Dichlorine hexoxide

Dichlorine hexoxide is the chemical compound with the molecular formula Cl₂O₆ or O₂Cl−O−ClO₃, 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 [ClO₂]⁺[ClO₄]⁻, which may be thought of as the mixed anhydride of chloric and perchloric acids. This compound is a notable perchlorating agent.^[1]

Dichlorine hexoxide

Names
IUPAC name Dichlorine hexoxide
Other names Chlorine trioxide; Chloryl perchlorate; Chlorine(V,VII) oxide
Identifiers
CAS Number	12442-63-6 Y
3D model (JSmol)	Interactive image Interactive image
ChemSpider	9564507 incorrect charge
PubChem CID	101946322
InChI InChI=1S/Cl2O6/c3-1(4)8-2(5,6)7 Key: BMVIIZAOKBSWDS-UHFFFAOYSA-N
SMILES O=[Cl](=O)O[Cl](=O)(=O)=O O=[Cl+]=O.[O-]Cl(=O)(=O)=O
Properties
Chemical formula	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)
Solubility in water	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). Y verify (what is YN ?) Infobox references

Molecular structure

It was originally reported to exist as the monomeric chlorine trioxide ClO₃ in gas phase,^[2] but was later shown to remain an oxygen-bridged dimer after evaporation and until thermal decomposition into chlorine perchlorate, Cl₂O₄, and oxygen.^[3] The compound ClO₃ was then rediscovered.^[4]

It is a dark red fuming liquid at room temperature that crystallizes as a red ionic compound, chloryl perchlorate, [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

Cl₂O₆ is diamagnetic and is a very strong oxidizing agent. Although stable at room temperature, it explodes violently on contact with organic compounds^[5] It is a strong dehydrating agent:

Cl₂O₆ + H₂O → HClO₄ + HClO₃

Many reactions involving Cl₂O₆ reflect its ionic structure, [ClO₂]⁺[ClO₄]⁻, including the following:^[6]

NO₂F + Cl₂O₆ → [NO₂]⁺ClO−4 + ClO₂F

NO + Cl₂O₆ → [NO]⁺ClO−4 + 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

It reacts with gold to produce the chloryl salt [ClO₂]⁺[Au(ClO₄)₄]⁻:^[7]

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 ClO₃ radical:^{[citation needed]}

2 AsF₅ + Cl₂O₆ → 2 ClO₃AsF₅

Synthesis

4 ClO₂ + 2 O₃ → 2 Cl₂O₆ + O₂ (under ultraviolet light)