(Dimethyl sulfoxide-κO)bis(thiosemicarbazide-κ2 N 1,S)zinc dipicrate dimethyl sulfoxide solvate monohydrate

The title complex, [Zn(CH5N3S)2(C2H6OS)](C6H2N3O7)2·C2H6OS·H2O, is composed of a [Zn(thiosemicarbazide)2(DMSO)]2+ cation (where DMSO is dimethyl sulfoxide), and two picrate anions. In the asymmetric unit, there is also a solvent molecule of DMSO and a water molecule of crystallization. In the cation, the ZnII atom is five-coordinated in a distorted square–pyramidal geometry. It coordinates to the O atom of a DMSO molecule and to the S and one N atom of two thiosemicarbazide molecules, which behave as bidentate ligands coordinating in a trans arrangement. In the crystal, a number of N—H⋯O, O—H⋯O and N—H⋯S hydrogen bonds link the molecules into two-dimensional networks. These networks are further linked via weak C—H⋯O interactions, forming a three-dimensional arrangement. Positional disorder in one methyl group of the coordinated DMSO molecule and in the two picrate anions was observed.

The title complex, [Zn(CH 5 N 3 S) 2 (C 2 H 6 OS)](C 6 H 2 N 3 O 7 ) 2 Á-C 2 H 6 OSÁH 2 O, is composed of a [Zn(thiosemicarbazide) 2 -(DMSO)] 2+ cation (where DMSO is dimethyl sulfoxide), and two picrate anions. In the asymmetric unit, there is also a solvent molecule of DMSO and a water molecule of crystallization. In the cation, the Zn II atom is five-coordinated in a distorted square-pyramidal geometry. It coordinates to the O atom of a DMSO molecule and to the S and one N atom of two thiosemicarbazide molecules, which behave as bidentate ligands coordinating in a trans arrangement. In the crystal, a number of N-HÁ Á ÁO, O-HÁ Á ÁO and N-HÁ Á ÁS hydrogen bonds link the molecules into two-dimensional networks. These networks are further linked via weak C-HÁ Á ÁO interactions, forming a three-dimensional arrangement. Positional disorder in one methyl group of the coordinated DMSO molecule and in the two picrate anions was observed.

Data collection
Bruker SMART APEX CCD areadetector diffractometer 18781 measured reflections 7719 independent reflections 6573 reflections with I > 2(I) R int = 0.021 Refinement R[F 2 > 2(F 2 )] = 0.034 wR(F 2 ) = 0.095 S = 1.05 7719 reflections 546 parameters 6 restraints H atoms treated by a mixture of independent and constrained refinement Á max = 0.54 e Å À3 Á min = À0.37 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). Thosemicarbazide, a well known chelating agent, is used to characterize aldehydes, ketones, and polysaccharides. Some thiosemicarbazide derivatives are potential anti-tumor, anti-hypertensive agents, and are active against influenza, protozoa and smallpox (Gowda & Mahadevappa, 1977;Pillai et al., 1977). Thiosemicarbazide is also used as a masking agent to minimize interference from metals such as copper, nickel and platinum in the determination of arsenic by atomic absorption methods (Kirkbright & Taddia, 1978). The conformational preferences of thiosemicarbazide in metal-complex formation are therefore of some interest. The reaction of zinc chloride with thiosemicarbazide in the presence of picric acid gave a yellow powder that was recrystallized using DMSO. This lead to the formation of yellow crystals of the title compoud, a DMSO-water solvate.
The molecular structure of the title complex is illustrated in Fig. 1. In the cation [Zn(thiosemicarbazide) 2 (DMSO)] 2+ the thiosemicarbazide ligands coordinate in a bidentate mode, bonding to atom Zn1 through atoms S1, N1 and S2, N4, in a trans arrangment. Atom Zn1 is also coordinated to a DMSO molecule through the O-atom, O1. The zinc atom has a distorted square pyramidal coordination sphere with a τ value of 0.17 [τ = 0 for square pyramidal, τ = 1 for trigonal bipyramidal; Addison et al., 1984]. The bond distances are comparable to those in a related penta-coordinated complex, (Citraconato-O)-bis(thiosemicarbazide-N,S)-zinc(II) monohydrate (Babb et al., 2003). Interestingly, here the thiosemicarbazide ligands are in a cis disposition, and the zinc coordination sphere has a τ value of 0.72, hence it can be described as a distorted trigonal bipyramid.
In the crystal a sheet-like network is formed, propagating in the ac-plane, as a result of a number of intermolecular N-H···O, O-H···O and N-H···S hydrogen bonds. These sheets are then linked via weak C-H···O interactions to form a three-dimensional arrangement (Table 1 and Fig. 2).

Experimental
A mixture of supersaturated solutions of thiosemicarbazide, picric acid and zinc chloride were added in the molar ratio of 1:1:1 (0.9 g: 2.5 g: 2.8 g). The calculated amount of thiosemicarbazide and zinc chloride were dissolved in distilled water and picric acid dissolved in acetone was added. Within a few minutes, the solution became turbid. The reaction was ensured with continuous stirring and after 1 h a yellow product was deposited at the bottom of the beaker, it was filtered off and dried. This yellow solid was recrystallized from DMSO to afford yellow block-like crystals of the title compound (yield: 4 g, 66.6%)