A new monoclinic polymorph, ?-K4Ge4Se10 (tetra-potassium deca-selenidotetra-germanate), that crystallizes in space group P21/c has been isolated. The structure contains isolated super-tetra-hedral adamantane [Ge4Se10]4- clusters identical to those in the known K4Ge4Se10 polymorph (P21/m), held together in in the crystal structure by ionic inter-action with the K+ ions. The adamantane unit, [Ge4Se10] 4-, is formed by corner-sharing of four GeSe4 tetra-hedra, with average Ge -. Se distances of 2.378 and 2.281 Å for (Ge - Se)endo and (Ge - Se)exo, respectively. There are four crystallographically distinct K + ions in ?-K4Ge4Se10 having coordination numbers of 5, 7. and 8 ( 2), with K - Se distances in the range 2.986 (2)-3.888 (1) Å, while the coordination numbers of the three unique K+ ions in the known K4Ge4Se10 (P21/m) vary between 5. and 7. Besides the differences in coordination numbers of K+ ions, the two polymorphs also exhibit a. different packing of the adamantane units.
A. Choudhury et al., "A Polymorph of K₄Ge₄Se₁₀," Acta Crystallographica Section E: Structure Reports Online, vol. 63, no. 7, pp. i155-i155, Wiley-Blackwell (IUCr), Jun 2007.
The definitive version is available at https://doi.org/10.1107/S1600536807023264
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01 Jun 2007