Europium(III) chloride is an inorganic compound with the formula EuCl<sub>3</sub>. The anhydrous compound is a yellow solid. Being hygroscopic it rapidly absorbs water to form a white crystalline hexahydrate, EuCl<sub>3</sub>÷6H<sub>2</sub>O, which is colourless. The compound is used in research.
Treating Eu<sub>2</sub>O<sub>3</sub> with aqueous HCl produces hydrated europium chloride (EuCl<sub>3</sub>÷6H<sub>2</sub>O). This salt cannot be rendered anhydrous by heating. Instead one obtains an oxychloride. Anhydrous EuCl<sub>3</sub> is often prepared by the "ammonium chloride route," starting from either Eu<sub>2</sub>O<sub>3</sub> or hydrated europium chloride (EuCl<sub>3</sub>÷6H<sub>2</sub>O) by heating carefully to 230 ðC. These methods produce (NH<sub>4</sub>)<sub>2</sub>[EuCl<sub>5</sub>]:
The pentachloride decomposes thermally according to the following equation:
The thermolysis reaction proceeds via the intermediary of (NH<sub>4</sub>)[Eu<sub>2</sub>Cl<sub>7</sub>].
Europium(III) chloride is a precursor to other europium compounds. It can be converted to the corresponding metal bis(trimethylsilyl)amide via salt metathesis with lithium bis(trimethylsilyl)amide. The reaction is performed in THF and requires a period at reflux.
Eu(N(SiMe<sub>3</sub>)<sub>2</sub>)<sub>3</sub> is a starting material for the more complicated coordination complexes.
Reduction with hydrogen gas with heating gives EuCl<sub>2</sub>. The latter has been used to prepare organometallic compounds of europium(II), such as bis(pentamethylcyclopentadienyl)europium(II) complexes. Europium(III) chloride can be used as a starting point for the preparation of other europium salts.
In the solid state, it crystallises in the UCl<sub>3</sub> motif. The Eu centres are nine-coordinate.