Bis{4-phenyl-1-[1-(pyridin-2-yl-κN)ethylidene]thiosemicarbazidato-κ2 N 1,S}cadmium

The reaction of cadmium acetate dihydrate with 2-acetylpyridine (4-phenylthiosemicarbazone) yielded the title compound, [Cd(C14H13N4S)2]. The CdII atom is six-coordinated in a distorted octahedral environment by two deprotonated thiosemicarbazone ligands acting in a tridentate chelating mode through two N and one S atoms, forming metalla-rings. In the crystal, molecules are connected through inversion centers via pairs of N—H⋯S interactions, building a one-dimensional hydrogen-bonded polymer along [0-1-1].

The reaction of cadmium acetate dihydrate with 2-acetylpyridine (4-phenylthiosemicarbazone) yielded the title compound, [Cd(C 14 H 13 N 4 S) 2 ]. The Cd II atom is six-coordinated in a distorted octahedral environment by two deprotonated thiosemicarbazone ligands acting in a tridentate chelating mode through two N and one S atoms, forming metalla-rings. In the crystal, molecules are connected through inversion centers via pairs of N-HÁ Á ÁS interactions, building a onedimensional hydrogen-bonded polymer along [011].

Experimental
Crystal data [Cd(C 14  H atoms treated by a mixture of independent and constrained refinement Á max = 0.75 e Å À3 Á min = À0.49 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). We gratefully thank Professor Dr Manfredo Hö rner (Federal University of Santa Maria, Brazil) for his help and support with the X-ray measurements. We also acknowledge the financial support through the DECIT/SCTIE-MS-CNPq-FAPERGS-Pronem-# 11/2029-1 and PRONEX-CNPq-FAPERGS projects. Schwederski, 1995), making the cadmium coordination chemistry very attractive. As part of our study of thiosemicarbazone derivatives, we report herein the synthesis and the crystal structure of a new Cd II complex with 2-acetylpyridine-(4-phenylthiosemicarbazone).
In the title compound, in which the molecular structure unit matches the asymmetric unit, the Cd II ion is six-coordinated in a distorted octahedral environment by two deprotonated 2-acetylpyridine-(4-phenylthiosemicarbazone) ligands acting in a tridentate chelating mode, forming five-membered rings (Fig. 1). The selected bond angles formed between donor atoms trough the Cd1 atom are N6-Cd1-N2 = 151.43 (7)°, N1-Cd1-S1 = 134.61 (5)° and N5-Cd1-S2 = 143.06 (5)° and show clearly a distorted octahedral environment. The displacement from ideal coordination geometry is probably a consequence of the geometrical requirements of the ligand and of crystal packing interactions.
The two ligands are coordinated to the Cd II ion in their meridional conformations with the S1/S2 thiolate and the N1/N5 pyridyl atoms cis to each other, while the N2/N6 azomethine atoms are trans to each other. A similar meridional conformation has also been observed in the Mn II complex with the same thiosemicarbazone ligand (Kovala-Demertzi et al., 2005) and in several Cd II complexes with tridentate "NNS"-chelating ligands derived from thiosemicarbazones (Ali et al., 2002). The two ligands show a Z-E-Z conformation for the donor atoms about the C1-C6/C6-N2/N3-C8 and the C15-C20/C20-N6/N7-C22 bonds, respectively.
Stirring was maintained for 30 min, while the reaction mixture turns yellow. A solution of cadmium acetate dihydrate (1 mmol) also in ethanol was added under continuous stirring and under slight warming to 60 °C. After 3 h a yellow solid was formed. This solid was filtered-off, washed with small portions of cool ethanol and dried at room conditions. Yellow crystals of the complex, suitable for X-ray analysis, were obtained by recrystallization from a 2:1 mixture of acetone and dimethylformamide.

Refinement
H atoms attached to C atoms were positioned with idealized geometry and were refined isotropic with U eq (H) set to 1.2 times of the U eq (C) for the aromatic and 1.5 times of the U eq (C) for methyl H atoms using a riding model with C-H = 0.93 Å and C-H = 0.96 Å, respectively. H atoms attached to N atoms were located in difference Fourier maps. Their positional and isotropic displacement parameters were refined.  The molecular structure of the title compound with labeling and displacement ellipsoids drawn at the 40% probability level.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq