trans-Chlorido(dimethyl sulfoxide-κS)(pyridine-2-carboxylato-κ2 N,O)platinum(II)

In the title complex, [Pt(C6H4NO2)Cl(C2H6OS)], the PtII ion is in a distorted square-planar environment defined by the N and O atoms from the chelating pyridine-2-carboxylate (pic) anionic ligand, one S atom of the dimethyl sulfoxide molecule and one Cl ion. The complex is disposed about a crystallographic mirror plane parallel to the ac plane passing through all the atoms of the complex except the methyl atoms of the dimethyl sulfoxide. The molecules are stacked in columns along the b axis with a Pt⋯Pt distance of 4.9508 (5) Å. Within the column, intermolecular C—H⋯O hydrogen bonds and weak π–π interactions between adjacent pyridine rings are present, the shortest centroid–centroid distance being 5.153 (4) Å.

In the title complex, [Pt(C 6 H 4 NO 2 )Cl(C 2 H 6 OS)], the Pt II ion is in a distorted square-planar environment defined by the N and O atoms from the chelating pyridine-2-carboxylate (pic) anionic ligand, one S atom of the dimethyl sulfoxide molecule and one Cl ion. The complex is disposed about a crystallographic mirror plane parallel to the ac plane passing through all the atoms of the complex except the methyl atoms of the dimethyl sulfoxide. The molecules are stacked in columns along the b axis with a PtÁ Á ÁPt distance of 4.9508 (5) Å . Within the column, intermolecular C-HÁ Á ÁO hydrogen bonds and weakinteractions between adjacent pyridine rings are present, the shortest centroid-centroid distance being 5.153 (4) Å .
The title complex, [Pt(C 6 H 4 NO 2 )Cl(C 2 H 6 OS)], crystallized in the orthorhombic space group Pnma, whereas, in the previously reported X-ray structure analysis, the complex crystallized in the monoclinic space group P2 1 /n (Annibale et al., 1986). The Pt II ion lies in a distorted square-planar environment defined by the N and O atoms from the chelating pyridine-2-carboxylate (pic) anionic ligand, one S atom of the dimethyl sulfoxide molecule and one Cl ion (Fig. 1). The tight O1-Pt1-N1 chelate angle [81.0 (2)°] results in non-linear trans axes [<O1-Pt1-S1 = 177.70 (16)° and <N1-Pt1-Cl1 Table 1). The complex is disposed about a crystallographic mirror plane parallel to the ac plane passing through all the atoms of the complex at the special positions (x,1/4,z), except the methyl atoms of the dimethyl sulfoxide ( Fig. 2). The molecules are stacked in columns along the b axis with a Pt···Pt distance of 4.9508 (5) Å. In the column, intermolecular C-H···O hydrogen bond (Table 2) and weak π-π interactions between adjacent pyridine rings are present, the shortest centroid-centroid distance being 5.153 (4) Å, and the ring planes are parallel and shifted for 3.807 Å. The intramolecular C-H···O and C-H···Cl hydrogen bonds are also observed (Table 2).

Experimental
Single crystals of the title complex were unexpectedly obtained by reacting K 2 PtCl 4 (0.2000 g, 0.482 mmol) and pyridine-2-carboxylic acid (0.1192 g, 0.968 mmol) in H 2 O (10 ml) under reflux for 5 h. Crystals suitable for X-ray analysis were obtained by slow evaporation from a dimethyl sulfoxide solution of the pale yellow reaction product at 80 °C.

Refinement
H atoms were positioned geometrically and allowed to ride on their respective parent atoms [C-H = 0.95 (aromatic) or 0.98 Å (CH 3 ) and U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C)]. The highest peak (2.60 e Å -3 ) and the deepest hole (-0.79 e Å -3 ) in the difference Fourier map are located 0.87 and 1.04 Å, respectively, from the atom Pt1.

Special details
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 > σ(F 2 ) is used only for calculating Rfactors(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.