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:[1]
The thermal decomposition of meta-periodic acid in vacuum also leads to the formation of diiodine hexoxide.[1]
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:
The compound is diamagnetic, which is attributed to the different oxidation numbers of the iodine atoms.[1] Structurally, the compound is iodyl periodate, an iodine(V,VII) oxide approximating IO2+IO4−.[1] 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.