Europium(III) iodide

Europium(III) iodide is an inorganic compound containing europium and iodine with the chemical formula EuI3.

Preparation
Europium metal reacts directly with iodine to form europium(III) iodide:
 * 2 Eu + 3 I2 → 2 EuI3

Hydrated europium(III) iodide can be prepared dissolving europium(III) oxide or europium(III) carbonate in hydroiodic acid:


 * Eu2O3 + 6 HI + 6 H2O → 2 EuI3*9H2O

Europium powder reacts with iodine in THF to form a THF adduct of europium(III) iodide:


 * 2 Eu + 3 I2 + 7 THF → [EuI2(THF)5][EuI4(THF)2]

The adduct can be formulated more simply as EuI3(THF)3.5.

Structure
Europium(III) iodide adopts the bismuth(III) iodide (BiI3) crystal structure type, with octahedral coordination of each Eu3+ ion by 6 iodide ions.

Reactivity
Europium(III) iodide is used as the starting material for two of the main ways of preparing europium(II) iodide:

Reduction with hydrogen gas at 350 °C:
 * 2 EuI3 + H2 -> 2 EuI2 + 2 HI

Thermal decomposition at 200 °C, a disproportionation reaction:
 * 2 EuI3 -> 2 EuI2 + 2 I2

Europium(III) iodide nonahydrate, EuI3·9H2O, thermally decomposes to europium(II) iodide dihydrate, EuI2·H2O.