Diammonium hexakis(thiocyanato-jN)- rhenate(IV) dimethyl sulfone tetra- solvate Andrzej Kochel a * and Malgorzata Holyn ´ska b a Faculty of Chemistry, University of Wroclaw, 14 Joliot-Curie Street, 50-383 Wroclaw, Poland, and b Fachbereich Chemie der Philipps-Universitaet, Hans- Meerwein-Strasse, D-35043 Marburg, Germany Correspondence e-mail: garfild9@gazeta.pl Received 10 February 2011 Accepted 21 March 2011 Online 14 April 2011 The title compound, (NH 4 ) 2 [Re(NCS) 6 ]4C 2 H 6 O 2 S, was ob- tained by solvothermal synthesis as part of a project on rhenium thiocyanate catalysts and starting materials for further aggregation to molecular magnets. The compound is the ammonium salt of octahedral hexakis(thiocyanato-N)- rhenate(IV) anions, which lie on centres of inversion. The dimethyl sulfone solvent molecules are involved in R 4 2 (8) and D N—HO hydrogen-bonded motifs. N—HS and SS short contacts are also present. Hydrogen-bonded ammo- nium–dimethyl sulfone layers alternate with layers formed by the complex anion (with SS short contacts) parallel to (100). Comment Rhenium thiocyanate complexes possess catalytic activity, which makes them an alternative to the expensive catalyst methyltrioxidorhenium (MTO) (Dinda et al., 2009). Synthetic routes for the synthesis of such catalysts are still being explored, in particular through reductive thiocyanolysis (Dinda et al., 2009) or ligand exchange in hexachlorido- rhenates(IV) (Gonzalez et al., 2008). Synthetic difficulties arise in connection with product purification. The title compound, (I), was obtained as part of a project on synthetic routes for providing new rhenium catalysts and reagents for further syntheses of new polynuclear materials. Compound (I) is a product of the reaction of ammonium thiocyanate and ammonium hexachloridorhenate(IV), carried out under solvothermal conditions (see reaction scheme). The solvent, dimethyl sulfone (m.p. 382 K), proves to be suitable under these conditions for ligand exchange in the hexa- chloridorhenate(IV) anion. The structure of (I) contains rare centrosymmetric hexa- kis(thiocyanato-N)rhenate(IV) anions (Fig. 1). To date, only a modest amount of crystal data has been reported for this anion, namely for a tetraphenylphosphonium salt (Dinda et al., 2009), and for a tetrabutylammonium salt along with its linkage isomer (Gonzalez et al., 2008). In both these cases, the anions are also centrosymmetric. Spectroscopic and magnetic data for a tetraphenylarsonium salt are available (Malecka et al., 2002). Reports of dimethyl sulfone are scarce in the literature; it has been observed on its own (Sands, 1963; Langs et al., 1970; Fronczek, 2006, 2007), as a solvent (Bandy et al. , 1981; Coles et al. , 2003) and as a ligand (Cotton & Felthouse, 1981; Dikarev et al. , 2003; Biagini et al., 2004), and has been observed to participate in discrete hydrogen-bonded motifs. The octahedral geometry of the anion of (I) (Table 1) can be compared with those found for the tetraphenylphosphonium and tetrabutylammonium salts (Dinda et al., 2009; Gonzalez et al., 2008). In (I), all the Re—N bond lengths are almost equal, while in both of the previously reported structures, some metal-organic compounds m134 # 2011 International Union of Crystallography doi:10.1107/S0108270111010535 Acta Cryst. (2011). C67, m134–m136 Acta Crystallographica Section C Crystal Structure Communications ISSN 0108-2701 Figure 1 The components of (I), with displacement ellipsoids drawn at the 30% probability level. [Symmetry code: (i) x + 1, y + 1, z.]