Received 12 September 2013
The crystal structure of strontium diarsenate has been reinvestigated from single-crystal X-ray diffraction data. In contrast to the previous determinations of this structure [Weil et al. (2009). Solid State Sci. 11, 2111-2117; Edhokkar et al. (2012). Mater. Sci. Eng., 28, 012017] and to all isotypic A2B2O7 compounds that crystallize in the space group P41, the current redetermination revealed the P43 enantiomorph of Sr2As2O7 with a purity of 96.3 (8)%. The crystal structure is made up from two eclipsed As2O7 diarsenate groups (symmetry 1) with characteristically longer As-O bridging bonds [1.756 (4)-1.781 (4) Å] than the terminal As-O bonds [1.636 (4)-1.679 (4) Å] and four Sr2+ sites with coordination numbers ranging from seven to nine. The building units are arranged in sheets parallel to (001).
The crystal structure of Sr2As2O7 has previously been refined from X-ray powder diffraction data (Weil et al., 2009) in the space group P41 and was later reinvestigated (Edhokkar et al., 2012). For isotypic structures crystallizing in space group P41, see: Baglio & Dann (1972); Webb (1966); Boudin et al. (1993); Müller-Bunz & Schleid (2000); Deng & Ibers (2005). For general structural features of the pyroarsenate anion, see: Weil & Stöger (2010).
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999) and ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2770 ).
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