Received 26 August 2013
The structure of tetrasodium pentadecamolybdenum nonadecaselenide, Na3.88Mo15Se19, is isotypic with the In3+xMo15Se19 compounds [Grüttner et al. (1979). Acta Cryst. B35, 285-292]. It is characterized by two cluster units, Mo6Sei8Sea6 and Mo9Sei11Sea6 (where i represents inner and a apical atoms), that are present in a 1:1 ratio. The cluster units are centered at Wyckoff positions 2b and 2c and have point-group symmetry -3 and -6, respectively. The clusters are interconnected through additional Mo-Se bonds. In the title compound, the Na+ cations replace the trivalent as well as the monovalent indium atoms present in In3.9Mo15Se19. One Mo, one Se and one Na atom are situated on mirror planes, and two other Se atoms and one Na atom [occupancy 0.628 (14)] are situated on threefold rotation axes. The crystal studied was twinned by merohedry with refined components of 0.4216 (12) and 0.5784 (12).
For previous reports on the crystal structures of In3Mo15Se19 compounds, see: Grüttner et al. (1979). For physical properties of this type of compounds, see: Seeber et al. (1979). The crystal structures of the substituted selenides Ho0.76In1.68Mo15Se19 and In0.87K2Mo15Se19 were reported by Salloum et al. (2006, 2007). For the isotypic sulfides In3.7Mo15S19, In1.6Rb2Mo15S19, In2.2CsMo15S19 and ScTl2Mo15S19, see: Salloum et al. (2004a,b); Gougeon et al. (2010). For details of the i- and a-type ligand notation, see: Schäfer & von Schnering (1964).
Data collection: COLLECT (Nonius, 1998); cell refinement: COLLECT; data reduction: EVALCCD (Duisenberg, 1998); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Bergerhoff, 1996); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RU2054 ).
Intensity data were collected on the Nonius KappaCCD X-ray diffactometer system of the Centre de diffractométrie de l'Université de Rennes I (www.cdifx.univ-rennes1.fr).
Altomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115-119.
Bergerhoff, G. (1996). DIAMOND. University of Bonn, Germany.
Duisenberg, A. J. M. (1998). PhD thesis, University of Utrecht, The Netherlands.
Gougeon, P., Gall, P., Salloum, D. & Potel, M. (2010). Acta Cryst. E66, i73.
Grüttner, A., Yvon, K., Chevrel, R., Potel, M., Sergent, M. & Seeber, B. (1979). Acta Cryst. B35, 285-292.
Meulenaer, J. de & Tompa, H. (1965). Acta Cryst. 19, 1014-1018.
Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.
Salloum, D., Gautier, R., Gougeon, P. & Potel, M. (2004a). J. Solid State Chem. 177, 1672-1680.
Salloum, D., Gougeon, P. & Potel, M. (2006). Acta Cryst. E62, i83-i85.
Salloum, D., Gougeon, P. & Potel, M. (2007). Acta Cryst. E63, i8-i10.
Salloum, D., Gougeon, P., Roisnel, T. & Potel, M. (2004b). J. Alloys Compd, 383, 57-62.
Schäfer, H. & von Schnering, H. G. (1964). Angew. Chem. 76, 833-845.
Seeber, B., Decroux, M., Fisher, Ø., Chevrel, R., Sergent, M. & Grüttner, A. (1979). Solid State Commun. 29, 419-423.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Spek, A. L. (2009). Acta Cryst. D65, 148-155.