Coordination Polyhedra ScX_n (X = O, S, Se, Te)
in Crystal Structures

V. N. Serezhkin*, G. V. Kryuchkova*, and V. S. Kazakevich**

* Samara State University, ul. Akademika Pavlova 1, Samara, 443011 Russia

** Lebedev Physical Institute, Samara Branch, Russian Academy of Sciences,
ul. Novo-Sadovaya 221, Samara, 443011 Russia

Received December 20, 2002

Abstract—Crystal-chemical analysis of 175 compounds containing 257 crystallographic types of scandium
atoms incorporated in ScX_n coordination polyhedra (X = O, S, Se, Te) has been performed with the use of
Voronoi–Dirichlet (VD) polyhedra and the intersecting spheres method. The effect of the nature of chalcogens
on the characteristics of scandium VD polyhedra and on the major features of scandium stereochemistry has
been surveyed. This analysis shows that Sc(III) can coordinate five to ten oxygen atoms, six or seven sulfur
atoms, or six Se atoms, whereas Sc(II) forms only ScX₆ octahedra (X = S, Se, Te). Tellurides also contain Sc(I)
and Sc(0.75) atoms, which coordinate, respectively, two to five and one to five tellurium atoms and concurrently
form two to six and one to eight Sc–Sc bonds. The effect of the nature of chalcogen atoms on the composition
and topology of [Sc_aX_b] complex entities is considered. Parameters of VD polyhedra can be used for revealing
errors in crystal structural databases.

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