Scandium triiodide

Scandium triiodide, also known as scandium iodide, is an inorganic compound with the formula ScI3 and is classified as a lanthanide iodide. This salt is a yellowish powder.[1] It is used in metal halide lamps together with similar compounds, such as caesium iodide, because of their ability to maximize emission of UV and to prolong bulb life. The maximized UV emission can be tuned to a range that can initiate photopolymerizations.[2]

Scandium triiodide
Names
IUPAC name
Scandium triiodide
Other names
Scandium(III) iodide
Scandium(3+) triiodide
Triiodoscandium
Identifiers
3D model (JSmol)
ECHA InfoCard 100.034.956
EC Number
  • 238-469-0
UNII
  • InChI=1S/3HI.Sc/h3*1H;/q;;;+3/p-3
    Key: HUIHCQPFSRNMNM-UHFFFAOYSA-K
  • [Sc](I)(I)I
Properties
ScI3
Molar mass 425.66
Appearance Yellowish solid
Melting point 920 °C (1,690 °F; 1,190 K)
Related compounds
Other anions
 Scandium fluoride
Scandium chloride
Scandium bromide
Other cations
 Yttrium(III) iodide
Lutetium(III) iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Scandium triiodide adopts a structure similar to that of iron trichloride (FeCl3), crystallizing into a rhombohedral lattice. Scandium has a coordination number of 6, while iodine has a coordination number of 3 and is trigonal pyramidal.[3]

The purest scandium triiodide is obtained through direct reaction of the elements:[1]

2 Sc + 3 I2 → 2 ScI3

Alternatively, but less effectively, one can produce anhydrous scandium triiodide by dehydrating ScI3(H2O)6.

Further information
  • Tomasz Mioduski, Cezary Gumiski, and Dewen Zeng "Rare Earth Metal Iodides and Bromides in Water and Aqueous Systems. Part 1. Iodides" Journal of Physical and Chemical Reference Data 2012, vol. 41, 013104-1 to 013104-63. doi:10.1063/1.3682093

References
  1. Haeberle, N., 1973, Preparation of highly pure lanthanide iodides, Technisch-Wissenschaftliche Abhandlungen der Osram-Gesellschaft, v. 11, p. 285
  2. Brabham, D.E., Metal halide lamp for curing adhesives. U.S. Patent 6,888,312, March 1, 2011
  3. Men'kov, A. A., Komissarova, L. N., 1964, X-ray study of scandium iodide, Zhurnal Neorganicheskoi Khimii, v. 9, p. 766
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