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.
It is produced by reaction between chlorine dioxide and excess ozone:
2 ClO2 + 2 O3 → 2 ClO3 + 2 O2 → Cl2O6 + 2 O2Molecular 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 compounds5 It is a strong dehydrating agent:
Cl2O6 + H2O → HClO4 + HClO3Many 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 Cl2It reacts with gold to produce the chloryl salt [ClO2]+[Au(ClO4)4]−:7
2 Au + 6 Cl2O6 → 2 [ClO2]+[Au(ClO4)4]− + Cl2Several other transition metal perchlorate complexes are prepared using dichlorine hexoxide.
Nevertheless, it can also react as a source of the ClO3 radical:
2 AsF5 + Cl2O6 → 2 ClO3AsF5Synthesis
4 ClO2 + 2 O3 → 2 Cl2O6 + O2 (under ultraviolet light)References
Jean-Louis Pascal; Frédéric Favier (1998). "Inorganic perchlorato complexes". Coordination Chemistry Reviews. 178–180 (1): 865–902. doi:10.1016/S0010-8545(98)00102-7. /wiki/Doi_(identifier) ↩
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. /wiki/Bibcode_(identifier) ↩
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. /wiki/Doi_(identifier) ↩
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. /wiki/Doi_(identifier) ↩
Mary Eagleson (1994). Concise encyclopedia chemistry. Walter de Gruyter. p. 215. ISBN 3-11-011451-8. 3-11-011451-8 ↩
Harry Julius Emeléus, Alan George Sharpe (1963). Advances in Inorganic Chemistry and Radiochemistry. Academic Press. p. 65. ISBN 0-12-023605-2. {{cite book}}: ISBN / Date incompatibility (help) 0-12-023605-2 ↩
Cunin, Frédérique; Catherine Deudon; Frédéric Favier; Bernard Mula; Jean Louis Pascal (2002). "First anhydrous gold perchlorato complex: [ClO2]+[Au(ClO4)4]−. Synthesis and molecular and crystal structure analysis". Inorganic Chemistry. 41 (16): 4173–4178. doi:10.1021/ic020161z. PMID 12160405. {{cite journal}}: templatestyles stripmarker in |title= at position 43 (help) /wiki/Doi_(identifier) ↩