Dysprosium(III) chloride

Dysprosium(III) chloride (DyCl₃), also known as dysprosium trichloride, is a compound of dysprosium and chlorine. It is a white to yellow solid which rapidly absorbs water on exposure to moist air to form a hexahydrate, DyCl₃·6H₂O. Simple rapid heating of the hydrate causes partial hydrolysis<ref name="Edel">F. T. Edelmann, P. Poremba, in: Synthetic Methods of Organometallic and Inorganic Chemistry, (W. A. Herrmann, ed.), Vol. 6, Georg Thieme Verlag, Stuttgart, 1997.</ref> to an oxychloride, DyOCl.

Preparation and reactions

DyCl₃ is often prepared by the "ammonium chloride route", starting from either Dy₂O₃ or the hydrated chloride DyCl₃·6H₂O.<ref> Template:Cite book </ref><ref name="Taylor">Template:Cite journal</ref><ref name="EdelmannPoremba1997">Template:Cite book</ref> These methods produce (NH₄)₂[DyCl₅]:

10 NH₄Cl + Dy₂O₃ → 2 (NH₄)₂[DyCl₅] + 6 NH₃ + 3 H₂O

DyCl₃·6H₂O + 2 NH₄Cl → (NH₄)₂[DyCl₅] + 6 H₂O

The pentachloride decomposes thermally according to the following equation:

(NH₄)₂[DyCl₅] → 2 NH₄Cl + DyCl₃

The thermolysis reaction proceeds via the intermediacy of (NH₄)[Dy₂Cl₇].

Treating Dy₂O₃ with aqueous HCl produces the hydrated chloride DyCl₃·6H₂O, which cannot be rendered anhydrous by heating. Instead one obtains an oxychloride:<ref name="Taylor"/>

DyCl₃ + H₂O → DyOCl + 2 HCl

Dysprosium(III) chloride is a moderately strong Lewis acid, which ranks as "hard" according to the HSAB concept. Aqueous solutions of dysprosium chloride can be used to prepare other dysprosium(III) compounds, for example dysprosium(III) fluoride:

DyCl₃ + 3 NaF → DyF₃ + 3 NaCl

Uses

Dysprosium(III) chloride can be used as a starting point for the preparation of other dysprosium salts. Dysprosium metal is produced when a molten mixture of DyCl₃ in eutectic LiCl-KCl is electrolysed. The reduction occurs via Dy²⁺, at a tungsten cathode.<ref>Y. Castrillejo, M. R. Bermejo, A. I. Barrado, R. Pardo, E. Barrado, A. M. Martinez, Electrochimica Acta, 50, 2047-2057 (2005).</ref>

Precautions

Dysprosium compounds are believed to be of low to moderate toxicity, although their toxicity has not been investigated in detail.

References

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