Dicyanidobis(thiourea-κS)cadmium(II) monohydrate

In the title compound, [Cd(CN)2(CH4N2S)2]·H2O, the Cd atom lies on a twofold rotation axis and is bonded to two S atoms of thiourea and two C atoms of the cyanide anions in a distorted tetrahedral environment. The crystal structure is stabilized by N—H⋯N(CN), N—H⋯O, O—H⋯N and N—H⋯S hydrogen bonds.

In the title compound, [Cd(CN) 2 (CH 4 N 2 S) 2 ]ÁH 2 O, the Cd atom lies on a twofold rotation axis and is bonded to two S atoms of thiourea and two C atoms of the cyanide anions in a distorted tetrahedral environment. The crystal structure is stabilized by N-HÁ Á ÁN(CN), N-HÁ Á ÁO, O-HÁ Á ÁN and N-HÁ Á ÁS hydrogen bonds.

Comment
The interest in cadmium(II) complexes of thiourea (Tu) arises because some of them exhibit non-linear optical properties (Rajesh et al., 2004) and they are useful for the convenient preparation of cadmium sulfide based semiconducting materials by their thermal decomposition in air (Stoev et al., 1994). Several crystallographic reports about cadmium(II) complexes of thiourea reveal that it coordinates to cadmium(II) via the sulfur atom (Corao et al., 1969;Marcos et al., 1998;Wang et al., 2002). Recently, we have reported the crystal structures of cadmium(II) complexes of N,N'-dimethylthiourea (Malik et al., 2010) and tetramethylthiourea (Tmtu), [Cd(Tmtu) 2 Br 2 ] (Nawaz et al., 2010a) and [Cd(Tmtu) 2 I 2 ] (Nawaz et al., 2010b). Herein, we report the crystal structure of a cadmium cyanide complex of thiourea, biscyanidobis(thiourea-kS)cadmium(II) monohydrate, [Cd(Tu) 2 (CN) 2 ].H 2 O. The present investigation was carried out in view of our continuous interest in the structural chemistry of cyanido complexes of d 10 metal ions with thiourea type ligands (Ahmad et al., 2009;Hanif et al., 2007).
In the title compound, the Cd atom is situated on a twofold axis of symmetry and is bonded to two cyanide carbon atoms and two sulfur atoms of thiourea ( Figure 1). The four coordinate metal ion adopts a severely distorted tetrahedral geometry, the bond angles being in the range of 95.76 (4) -143.5 (1) °. The Cd-S and Cd-C bond lengths are 2.6363 (5) Å and 2.211 (2) Å respectively. These are in agreement with those reported for related compounds (Marcos et al., 1998;Malik et al. 2010;Nawaz et al., 2010a,b;Wang et al., 2002;Yoshikawa et al., 2003). The two C-N bond lengths in thiourea, C2-N2 and C2-N3, are 1.312 (2) Å and 1.305 (2) Å respectively. The CNH 2 fragments of the two thiourea molecules are essentially planar, the maximum deviation from the mean plane being for the nitrogen atoms with 0.03 (1) Å. These values are consistent with a significant CN double bond character and electron delocalization in the SCN 2 moiety. To the best of our knowledge, this is the first X-ray structure of a cadmium complex having both sulfur containing ligands and cyanide in its coordination sphere.
The molecules pack to form columns parallel to the b direction ( Figure 2). Within these columns, each metal ion interacts with two sulfur atoms of a neighboring molecule (Cd···S: 3.3140 (5) Å), hence extending the tetra-coordinate inner-sphere to a hexa-coordinate outer-sphere with a distorted octahedral environment. These interactions confer to the molecular columns a polymeric chain character.
Intermolecular hydrogen bonding takes place through N-H···S as well as N-H···N(CN) interactions (Table 1). The complex molecules also interact with the water molecules through C-N···H-O and N-H···O bonds. In this scheme the water molecule is tetrahedrally hydrogen bonded to four complex molecules. This generates a three-dimensional hydrogen bonding network where the molecular chains are interconnected through hydrogen bonding either directly or through the water molecules.
supplementary materials sup-2 Experimental To 0.17 g (1.0 mmol) cadmium(II) cyanide (prepared by the reaction of CdCl 2 .H 2 O and KCN in 1:2 molar ratio in water) suspended in 15 mL water was added 2 equivalents of thiourea in methanol. Yellow precipitates formed, were filtered and the filtrate was kept for crystallization. Crystals were grown by slow evaporation of a water/methanol solution at room temperature.

Refinement
All non-H atoms were refined anisotropically. Hydrogen atoms were located in a difference Fourier map and freely refined isotropically. Fig. 1. The molecular structure of the title compound with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level (Symmetry code: i = 0.5-x, y, 0.5z).