trans-Bis(dimethyl sulfoxide-κO)bis(thiosemicarbazide-κ2 N 1,S)cadmium dipicrate dihydrate

In the cation of the title compound, [Cd(CH5N3S)2(C2H6OS)2](C6H2N3O7)2·2H2O, the CdII atom is located on an inversion center. It is hexacoordinated in an octahedral fashion by two thiosemicarbazide molecules, which coordinate in a bidentate manner via the S and N atoms, and to the O atom of two dimethyl sufoxide (DMSO) molecules. The charges are equilibrated by two picrate anions and the complex crystallizes as a dihydrate. In the crystal, these units are linked by a number of O—H⋯O and N—H⋯S hydrogen bonds and weak C—H⋯O interactions, forming a three-dimensional network.


Related literature
For the role of hydrogen bonding in the construction of supramolecular structures, see: Braga et al. (2004). For the crystal structure of a similar compound, see: Li et al. (2006).
Data collection: X-AREA (Stoe & Cie, 2009); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 Intermolecular and inter-ionic hydrogen bonding interactions, which are not only the strongest of the noncovalent interactions but also highly directional, play an important role in constructing supramolecular structures (Braga et al., 2004). Recently we have obtained crystals of the title compound from the reaction of thiosemicarbazide, picric acid and DMSO, and we report herein on its crystal structure.
In the cation of the title compound the cadmium(II) atom is hexa-coordinated to two thiosemcarbazide and to two DMSO molecules ( Fig. 1). This cation is centrosymmetric with the metal atom being located on an invesion center. The thiosemicarbazide molecules behave as bidentate ligands coordinating via atoms N3 and S1. The bond distances and angles are similar to those reported for a similar complex, bis(Thiosemicarbazide)-diaqua-cadmium(II) bis(maleate) dihydrate (Li et al., 2006).
In the crystal the cation, the picrate anions and the water molecules of crystallization are involved in N-H···O, O-H···O and N-H···S hydrogen bonds and C-H···O interactions, to form a three-dimensional supramolecular network (Table 1 and Fig. 2).

Experimental
The title compound was synthesized by reacting thiosemicarbazide, picric acid and cadmium bromide in a 2:1:1 (1.8 g: 2.5 g: 2.8 g) molar ratio. The calculated amount of thiosemicarbazide and cadmium bromide were dissolved in distilled water and the required amount of picric acid (dissolved in acetone) was added to the solution slowly with stirring. Within a few minutes the solution became turbid. The reaction was ensured with continous stirring. After 1 h a yellow salt was deposited at the bottom of the beaker and it was filtered off and dried. This solid was recrystallized in a DMSO solution to obtain yellow rod-like crystals of the title compound on slow evaporation of the solvent.

Refinement
The water molecule, the NH 2 and NH H-atoms were located in difference Fourier maps and were freely refined. The C-bound H atoms were included in calculated positions and treated as riding atoms; C-H = 0.95 Å and 0.98 Å for CH and methyl H-atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.2 for CH H-atoms, and k = 1.5 for methyl H-atoms.   Table 1 for details; C-bound H-atoms not involved in C-H···O interactions have been omitted for clarity].