Diiodine hexaoxide

Diiodine hexaoxide

Names
Other names iodine trioxide
Identifiers
CAS Number	65355-99-9
3D model (JSmol)	Interactive image
InChI InChI=1S/HIO4.IO2/c2-1(3,4)5;2-1-3/h(H,2,3,4,5);/q;+1/p-1 Key: XOXXWUXXUGTNSE-UHFFFAOYSA-M
SMILES O=[I+]=O.O=[I-](=O)(=O)=O
Properties
Chemical formula	I2O6
Molar mass	349.803 g·mol−1
Appearance	yellow crust or crystals
Density	4.53 g/cm3[1]
Melting point	150 °C (302 °F; 423 K) (dec.)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Diiodine hexaoxide, is a chemical compound of oxygen and iodine with the chemical formula I₂O₆. It belongs to the class of iodine oxides, and is a mixed oxide, consisting of iodine(V) and iodine(VII) oxidation states.

Reaction of periodic acid with iodic acid in sulfuric acid:^[2]

HIO₃ + H₅IO₆ → I₂O₆ + 3H₂O

The thermal decomposition of meta-periodic acid in vacuum also leads to the formation of diiodine hexoxide.^[2]

Below 100 °C, diiodine hexaoxide can be stored stably in the absence of moisture. When dissolved in water, an exothermic reaction to form iodine and periodic acid takes place. When heated above 150 °C, decomposition into diiodine pentoxide can be observed:

2 I₂O₆ → 2 I₂O₅ + O₂

The compound is diamagnetic, which is attributed to the different oxidation numbers of the iodine atoms.^[2] Structurally, the compound is iodyl periodate, an iodine(V,VII) oxide approximating IO₂⁺IO₄⁻.^[2] As a solid, the compound crystallizes in the space group P1 (space group no. 2) with the lattice constants a  = 500.6 pm, b  = 674.1 pm, c  = 679.5 pm, α = 97.1°, β = 96.43°, γ = 105.36° with one formula unit per unit cell.^[1]

• Diiodine tetroxide
• Orthoperiodic acid
• Diiodine pentoxide
• Iodine oxides

• David R. Lide (Hrsg.): CRC Handbook of Chemistry and Physics 96. Auflage. CRC Press / Taylor and Francis, Boca Raton FL, Properties of the Elements and Inorganic Compounds, S. 4-67.
• A. F. Holleman, N. Wiberg (2016). Anorganische Chemie. Grundlagen und Hauptgruppenelemente. Vol. 1. Berlin / Boston: Walter de Gruyter. p. 543. ISBN 978-3-11-049585-0.