Ethylenediammonium tetraaquadisulfatocadmate

The crystal structure of the title compound, [NH3(CH2)2NH3][Cd(SO4)2(H2O)4], consists of [Cd(SO4)2(H2O)4]2− anions that are built from octahedral Cd(H2O)4O2 and SO4 tetrahedral units linked by corner sharing. The ethylenediamminium cations are linked to the anions via N—H⋯O hydrogen bonds. The asymmetric unit contains one-half of the compound, the other half being related to the first by an inversion centre. The crystal structure presents alternate stacking of the inorganic and organic layers along the crystallographic b axis. The structure cohesion and stability is further assured by O(water)—H⋯O hydrogen bonds.

The crystal structure of the title compound, [NH 3 (CH 2 ) 2 NH 3 ]- [Cd(SO 4 ) 2 (H 2 O) 4 ], consists of [Cd(SO 4 ) 2 (H 2 O) 4 ] 2À anions that are built from octahedral Cd(H 2 O) 4 O 2 and SO 4 tetrahedral units linked by corner sharing. The ethylenediamminium cations are linked to the anions via N-HÁ Á ÁO hydrogen bonds. The asymmetric unit contains one-half of the compound, the other half being related to the first by an inversion centre. The crystal structure presents alternate stacking of the inorganic and organic layers along the crystallographic b axis. The structure cohesion and stability is further assured by O(water)-HÁ Á ÁO hydrogen bonds.
Grateful thanks are expressed to Dr T. Roisnel (Centre de Diffractomé trie X, Université de Rennes 1) for the X-ray data collection.

Comment
The chemistry of organic-inorganic hybrid materials has received increasing attention over the last few years, mainly with the idea of using amines as templates and associating transition metals. A great interest has been shown in some organically templated metal sulfate because of their open-framework structure and ferroelastic and ferroelectric propreties. We note also that a previous work of synthesis and characterization of mixed metal sulfates and amines, leading to many important physical properties, has been realized in our laboratory (Rekik et al., 2005;Naïli, et al., 2006;Rekik et al., 2007;Yahyaoui et al., 2007;Rekik et al., 2008;Rekik et al., 2009a). In the course of our investigations on new sulfate materials having interesting properties, we report here the chemical preparation and the structural characterization of a new ethylenediammonium cad- The title compound is isostructural with the manganese, iron, cobalt and magnesium related phases (Chaabouni et al., 1996;Held, 2003;Rekik et al., 2008;Rekik et al., 2009b). As it can be seen in figure 1, the crystal structure shows an alternate stacking of inorganic layers of tetraaquabis(sulfato-O)cadmium anions, [Cd(SO 4 ) 2 (H 2 O) 4 ] 2-, and organic layers of [NH 3 (CH 2 ) 2 NH 3 ] 2+ cations along the crystallographic b axis. Anions and cations are linked together through N-H···O hydrogen bonds to form a three-dimensional network. The asymmetric unit (Fig. 2) of the title compound contains only one cadmium atom located at a symmetry centre, only one sulfate tetrahedron and ethylendiammonium cation lying about inversion centre. The Cd(II) central atom is octahedrally coordinated by one oxygen atom of sulfate group, two water molecules and the corresponding centrosymmetrically located atoms. Each octahedron around Cd shares two oxygen atoms with two sulfate groups to form trimeric units. These latest are stabilized and linked via OW-H···O hydrogen bonds giving rise to a three-dimensional inorganic framework delimiting tunnels along the three crystallographic axes. The negative charge of the inorganic part is compensated by ethylediammonium cations which are located on inversion centres in the inorganic framework cavities. The structure cohesion and stability are assured by two types of hydrogen bonds, OW-H···O and N-H···O.

Experimental
Single-crystals of the title compound were grown by slow evaporation at room temperature of an aqueous solution of CdSO 4 .8(H 2 O)/C 2 H 8 N 2 /H 2 SO 4 in a ratio 1:1:1. The product was filtered off and washed with a small amount of distilled water.

Refinement
The aqua H atoms were located in difference map and refined with O-H distance restraints of 0.85 (2) Å and H-H distance restraints of 1.35 (2) Å. H atoms bonded to C and N atomswere positioned geometrically and allowed to ride on their parent atom, with C-H = 0.97 Å, N-H = 0.89 Å and U iso = 1.2U eq (C, N). The 1 1 3 reflection has been omitted, (Iobs/Ical)/sigma greater than 10.  Fig. 1. Projection of the crystal structure of the title compound along the a axis, with hydrogen bonds indicated as dashed lines. Fig. 2. A part of the crystal structure of the title compound showing the asymmetric unit (expanded by symmetry to give complete organic cation and trimeric unit) and atom numbering. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonds are represented by dashed lines.[Symmetry codes: (I) -x + 1, -y + 1, -z + 2; (II) -x + 2, -y + 2, -z + 1.]

Special details
Experimental. Data were corrected for Lorentz-polarization effects and an analytical absorption correction (de Meulenaer & Tompa, 1965) was applied. The structure was solved in the P -1 space group by the direct methods (Cd and S) and subsequent difference Fourier syntheses (all other atoms), with an exception for H atoms bonded to C and N atoms which are positioned geometrically.  (4)  O2 0.0200 (4) 0.0437 (6)  Geometric parameters (Å, °)