Dichloridobis[3-(4-methoxyphenyl)-2-methyl-5-(piperidin-1-yl)-2,3-dihydro-1,2,4-oxadiazole-κN 4]platinum(II)

In title compound, [PtCl2(C15H21N3O2)2], the PtII cation, located on an inversion center, is coordinated by two Cl− anions and two 3-(4-methoxyphenyl)-2-methyl-5-(piperidin-1-yl)-2,3-dihydro-1,2,4-oxadiazole ligands in a distorted Cl2N2 square-planar geometry. The dihydrooxadiazole and piperidine rings display envelope (with the non-coordinating N atom as the flap atom) and chair conformations, respectively. In the crystal, weak C—H⋯Cl hydrogen bonds link the molecules into supramolecular chains running along the b axis. The piperidine ring is disordered over two positions with the occupancy ratio of 0.528 (4):0.472 (4).


Experimental
Crystal data [PtCl 2 (C 15    In the past decade, a great attention has been paid to metal-mediated cycloaddition (CA) of dipoles to nitriles because the activation of nitrile substrates by a suitable metal center often results in promotion of CAs, which are not feasible in socalled pure organic chemistry (Coley et al., 2008, Wagner et al., 2010. Thus, the metal-mediated CA represents an efficient route to free and/or coordinated heterocycles that could be either difficult to obtain or even inaccessible via metal-free protocols (Bokach et al., 2006(Bokach et al., , 2011. Furthermore, an interest in 2,3-dihydro-1,2,4-oxadiazole and their platinum complexes is caused by their potential application in medicine. Despite 2,3-dihydro-1,2,4-oxadiazoles are known, examples of 5-dialkylamino-2,3-dihydro-1,2,4-oxadiazoles and, in particular, their metal complexes are rare. Therefore, the synthesis of new complexes bearing the rare heterocycles as ligands and investigation of their properties, including their biological activity, are of interest. As an amplification of our project focused on metal-mediated CA and reactivity of metal-bound dialkylcyanamides (Kritchenkov et al., 2011)) we synthesized and characterized the title compound by a single-crystal X-ray diffraction.
In the crystal structure, the complexes interact with each other via the weak C-H···Cl hydrogen bond (Table 2), forming the supramolecular chains running along the b axis.

Experimental
Title compound was synthesized and isolated as pure solid by the described method (Kritchenkov et al., 2011). The crystal was obtained by a slow evaporation of chloroform (RT) solution of the title compound. Hexane was added to the solution for improvement of crystallization of the complex.

Refinement
The piperidine ring was found to be disordered over two positions, the occupancies were refined to 0.528 (4)/0.472 (4). H atoms were placed in calculated positions with C-H = 0.93-0.98 Å and included in the refinement in the riding model approximation, U iso (H) set to 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for the others.

Figure 1
View to the C 30 H 42 Cl 2 N 6 O 4 Pt complex in the structure of 1. Thermal ellipsoids are drawn at the 50% probability level.

Special details
Experimental. The piperidine ring was found to be disordered over two positions with the occupancies 0.528/0.472. The non-hydrogen atoms were refined anisotropically. Carbon-and nitrogen-bonded H atoms were placed in calculated positions and were included in the refinement in the "riding" model approximation, with U iso (H) set to 1.5U eq (C) and C-H 0.96 Å for the methyl groups, 1.2U eq (C) and C-H 0.98 Å for the tertiary CH groups, 1.2U eq (C) and C-H 0.93 Å for the carbon atoms of the benzene rings, and 1.2Ueq(N) and N-H 0.91 Å for the tertiary NH groups. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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 Occ. (