Diiodine tetroxide

Diiodine tetraoxide, I2O4, is a chemical compound of oxygen and iodine. It belongs to the class of iodine oxides, and is a mixed oxide, consisting of iodine(III) and iodine(V) oxidation states.

Synthesis

The oxide is formed by the reaction of hot concentrated sulfuric acid on iodic acid for several days.

It is formed from diiodine pentoxide and iodine in concentrated sulfuric acid or iodosyl sulfate (IO)2SO4 added to water:

Physical properties

Diiodine tetraoxide is a yellow, granular powder, at 25°C at standard atmosphere (a pressure). At temperatures above 85 °C it decomposes to diiodine pentoxide and iodine:

This process is even faster at 135 °C. It dissolves in hot water to form iodate and iodide. Structurally, the compound is an iodyl iodite O2I-OIO (iodine(V,III) oxide) with bent IVO2 units (I–O distances 1.80 and 1.85 Å; ∠OIO angle 97°) and bent IIIIO2 units (IO distances 1.93 Å, OIO angle 95.8°). Both units are linked via I—O—I bridges to form polymeric zigzag chains (I2O4)x.

Diiodine tetraoxide has a monoclinic crystal structure with the space group P21/c (space group number 14). Unit cell dimensions are a = 8.483 b = 6.696 c = 8.333 Å and β = 124.69°. Unit cell volume = 389.15 Å3. Z = 4. Density is 2.57 Mg/m3

Reactions
Diiodine tetroxide oxidises hydrochloric acid:

References

Category:Iodine compounds
Category:Oxides