trans-Bis(5-amino-1,3,4-thiadiazol-2-thiolato-κS 2)bis(triphenylphosphane-κP)palladium(II) dimethyl sulfoxide disolvate hemihydrate

The title complex, [Pd(C2H2N3S2)2(C18H15P)2]·2C2H6OS·0.5H2O, was obtained from the reaction of trans-[(Ph3P)2PdCl2] with 5-amino-1,3,4-thiadiazole-2-thione (SSNH2) in a 2:1 molar ratio. The PdII atom, located in a crystallographic center of symmetry, has a square-planar geometry with two triphenylphosphine P-coordinated molecules and two SSNH2 ligands with the S atoms in a trans conformation. The latter ligand exhibits N—H⋯N hydrogen-bonding contacts formed by the amino group with the thiadiazole ring, generating a chain along the c axis. The asymmetric unit contains one half of the complex molecule along with disordered dimethyl sulfoxide and water molecules.

The title complex, [Pd(C 2 H 2 N 3 S 2 ) 2 (C 18 H 15 P) 2 ]Á2C 2 H 6 OSÁ-0.5H 2 O, was obtained from the reaction of trans-[(Ph 3 P) 2 PdCl 2 ] with 5-amino-1,3,4-thiadiazole-2-thione (SSNH 2 ) in a 2:1 molar ratio. The Pd II atom, located in a crystallographic center of symmetry, has a square-planar geometry with two triphenylphosphine P-coordinated molecules and two SSNH 2 ligands with the S atoms in a trans conformation. The latter ligand exhibits N-HÁ Á ÁN hydrogenbonding contacts formed by the amino group with the thiadiazole ring, generating a chain along the c axis. The asymmetric unit contains one half of the complex molecule along with disordered dimethyl sulfoxide and water molecules.

Related literature
For background to the design and synthesis of ligands that contain efficient metal coordination sites and hydrogenbonding functionalities, see: Beatty (2001). The SSNH 2 (5amino-1,3,4-thiadiazole-2-thiol) ligand exists in the thione and thiol forms and can converted into the thiolate form depending on the affinity of the metal, see: Tzeng et al. (1999). For SSNH 2 acting as a ligand and as auxiliary in the construction of hydrogen bonds in coordination compounds with Pd II , see: Tzeng, Lee et al. (2004), with Pt II , see: Tannai et al. (2006), with Cd II , see: Gao et al. (2009) and with Au I , see: Tzeng et al. (1999); Tzeng, Huang et al. (2004). For the thiolate form, see: Downie et al. (1972).

Experimental
Crystal data [Pd(C 2

Martínez and David Morales-Morales Comment
Hydrogen bonds are commonly used to generate supramolecular assemblies of coordination complexes, in this field an important area of research is the design and synthesis of ligands that contain efficient metal coordination sites and hydrogen bonding functionalities (Beatty, 2001). In this context the ligand 5-amino-1,3,4-thiadiazole-2-thiol (SSNH 2 ) has been used as building block for the construction of hydrogen bonded frameworks. The ligand SSNH 2 can exists in the thione and thiol forms, however it can converted into the thiolate form depending on the affinity of the metal (Tzeng, et al., 1999). Several reports of SSNH 2 acting as a ligand and as auxiliary in the construction of hydrogen bonds in coordination compounds with Pd(II) (Tzeng, Lee et al., 2004), Pt(II) (Tannai, et al., 2006), Cd(II) (Gao, et al., 2009) and Au(I) (Tzeng, et al., 1999;Tzeng, Huang et al., 2004) have been informed in the literature. Thus, in this opportunity we would like to report the crystal structure of the Pd(II) complex, trans-[(Ph 3 P) 2 Pd(SSNH 2 ) 2 ] DMSO, H 2 O.
The molecular structure of the title compound is shown in Figure 1. The selected bond distances and angles are listed in Table 1. Only half molecule of the complex is found in the asymmetric unit and an inversion operator is needed for the generation of a whole molecule. The Pd(II) atom in the complex exhibits a square-planar arrangement, however the geometry is forced by the steric hindrance and electronic repulsions due to the interactions between the phenyl and the heterocycle rings. The SSNH 2 ligands are bonded to the metal center by the sulfur atoms in a trans arrangement with the thiadiazole groups found out of the plane of the Pd(II) coordination environment. The distance C2-S2 confirms that the ligand exists in the thiolate form (Downie, et al., 1972). The free amine group of the ligand SSNH 2 forms a hydrogen bond N6-H6A···N4 with the nitrogen atom of the thiadiazole ring related by symmetry, generating a centrosymmetric eight-member cycle, that is extended along the c-axes to form a chain framework. These chains are kept together by weak C-H···π [C9-H9···Cg(C13-C18)] intermolecular interactions. The compound crystallized with one molecule of DMSO that exhibits disorder on its structure, and one molecule of water. Weak interactions of N6-H6B···O1 (DMSO) solvent and O2-H atom of the DMSO solvent are observed. Although the solvent molecules do not participate in the strong interactions, they are important in the stabilization of the compound in the crystal lattice.
After this time, a reddish-orangey precipitated was noted, and the solution was filtered under vacuum to afford compound trans-[(Ph 3 P) 2 Pd(SSNH 2 ) 2 ] (59 mg, 95% yield). Crystals suitable for single-crystal X-ray diffraction analysis were  The molecular structure of the title compound with displacement ellipsoids at the 30% probability, the hydrogen atoms,  The title compound is linked by N-H···N intermolecular interactions along the c axes, the hydrogen atoms for the interactions are drawn.

Crystal data
[Pd(C 2 H 2 N 3 S 2 ) 2 (C 18 H 15 P) 2 ]·2C 2 H 6 OS·0. Hydrogen site location: inferred from neighbouring sites H atoms treated by a mixture of independent and constrained refinement w = 1/[σ 2 (F o 2 ) + (0.0611P) 2 ] where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.63 e Å −3 Δρ min = −0.37 e Å −3 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.