Scandium(III) chloride

Scandium(III) chloride is an ionic compound also known as scandium chloride and scandium trichloride. It is composed of one scandium and three chlorine atoms. Each chlorine atom takes one of scandium’s three valence electrons, resulting in 3Cl^- and Sc³⁺. The ensuing formula is ScCl₃^[1].

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Chemical and physical properties

Scandium(III) chloride is a white crystalline solid with the formula ScCl₃. Typical for an ionic solid, it is high-melting, liquefying at 960 °C^[2]. Both exhibit hexagonal close-packed (hcp) crystal structures, but it is their bond energy that accounts for the melting points’ difference. Scandium(III) chloride is primarily of interest in the research laboratory and numerous suppliers (see below) offer both the anhydrous form and hexahydrate (ScCl₃•6H₂O).

Like other compounds of Sc, the chlorides are dominated by the III oxidation state. Interesting reduced forms of Sc can however be prepared by reducing the trichloride with Sc metal (see below).

Preparation^[3]

Scandium(III) chloride is synthesized by the action of hydrogen chloride on elemental scandium or scandium(III) oxide. Carbon tetrachloride can also be used:

2Sc_(s) + 6HCl_(l) → 2ScCl_3(s) + 3H_2(g)

Reactions of scandium(III) chloride

• Scandium(III) chloride’s was used in the first preparation of metallic scandium in 1937. Fischer and collaborators synthesized the metal through an electrolysis of a eutectic melt of scandium(III) chloride and other salts at 700-800 °C.^[4].
• Reaction of ScCl₃ with tetrahydrofuran yields ScCl₃(THF)₃ as white crystals. This THF-soluble complex is a key synthetic intermediate.
• ScCl₃ has been converted to its dodecyl sulfate salt, which is used as a "Lewis acid-surfactant combined catalyst" (LASC) in aldol-like reactions.
• ScCl₃ has proven to be reactive toward Sc metal to give rise to a broad family of scandium chlorides where the Sc has an oxidation state <3.

Sc_(s) + ScCl₃ (950 °C) → Sc₅Cl₈

Sc_(s) + ScCl₃ (890 °C) → Sc₇Cl₁₂ → Sc(Sc₆Cl₁₂)

Other uses

Scandium(III) chloride is found in halide lamps, optical fibers, electronic ceramics, and lasers^[5].

Handling and safety considerations

Scandium(III) chloride is hygroscopic it should be stored in a desiccator.

References

1. ^ Greenwood, N.N.; Earnshaw, A. (1998). Chemistry of the Elements (2nd Edition).
2. ^ Frederikse, H.P.R.; Lide, David R. (1998). CRC Handbook of Chemistry and Physics (78th Edition).
3. ^ Subbarao, E.C.; Wallace, W.E. (1980) Science and Technology of Rare Earth Metals. (Academic Press) pp. 16
4. ^ Metal Suppliers Online. (2000). Scandium Chloride.
5. ^ Metall Rare Earth Limited. (2006). Scandium Chloride

Journal citations

• Manzer, L. E., "Tetrahydrofuran Complexes of Selected Early Transition Metals", Inorganic Syntheses, 1982, volume 21, page 135-40.
• Hwu, S. J.; Dudis, D. S. and Corbett, J. D., "Synthesis, structure, and properties of the infinite-chain compounds scandium chloride carbide, Sc₅Cl₈C and scandium chloride nitride, Sc₅Cl₈N", Inorganic Chemistry, 1987, volume 26, page 469-73
• Corbett, J. D., "Trichlorides of the rare earth elements, yttrium, and scandium", Inorganic Syntheses, 1983, volume 22, page 39-42
• Meyer, G. and Corbett, J. D., "Reduced ternary halides of scandium: RbScX₃ (X = chlorine, bromine) and CsScX₃ (X = chlorine, bromine, iodine)", Inorganic Chemistry, 1981, volume 20, page 2627-31.
• Corbett, J. D.; Daake, R. L.; Poeppelmeier, K. R. and Guthrie, D. H., "Metal-metal bonded clusters in transition metal Groups 3 and 4. Synthesis and structure of three M₆ X₁₂-type clusters for scandium and zirconium", Journal of the American Chemical Society, 1978, volume 100, page 652-4.
• Poeppelmeier, K. R. and Corbett, J. D., "Metal-metal bonding in reduced scandium halides. Synthesis and crystal structure of scandium monochloride", Inorganic Chemistry, 1977, volume 16, page 294-7.