trans-Dichloridobis(4-nitroaniline-κN 1)palladium(II)

In the title compound, [PdCl2(C6H6N2O2)2], the PdII atom is coordinated in a distorted square-planar geometry by two N atoms from two 4-nitroaniline ligands and two Cl atoms in a trans arrangement. Intermolecular N—H⋯Cl hydrogen bonds involving the amino groups and chloride anions lead to a chain along [100]. These chains are further self-assembled into a three-dimensional network through N—H⋯O and N—H⋯Cl hydrogen bonds.

In the title compound, [PdCl 2 (C 6 H 6 N 2 O 2 ) 2 ], the Pd II atom is coordinated in a distorted square-planar geometry by two N atoms from two 4-nitroaniline ligands and two Cl atoms in a trans arrangement. Intermolecular N-HÁ Á ÁCl hydrogen bonds involving the amino groups and chloride anions lead to a chain along [100]. These chains are further self-assembled into a three-dimensional network through N-HÁ Á ÁO and N-HÁ Á ÁCl hydrogen bonds.
The author acknowledges Lanzhou Jiaotong University for supporting this work.

Tian-Jun Feng Comment
Palladium compounds have attracted much attention due to their applications in homogeneous and heterogeneous catalyses (Padmanabhan et al., 1985). Some dramatic results in the homogeneous catalysis of the reactions of organic compounds, particularly the successful commercial exploitation of the Wacker one stage process for the homogeneous catalytic oxidation of ethylene to acetaldehyde in the presence of palladium(II) chloride (Hartley, 1973), have contributed to this interest. In this paper, we report the crystal structure of the title compound, a new palladium(II) complex obtained by the reaction of 4-nitroaniline with palladium chloride in ethanol solution.
As illustrated in Fig. 1, the Pd II atom exhibits a distorted square-planar coordination geometry, defined by two N atoms from two 4-nitroaniline ligands and two chloride atoms. The molecule adopts the trans configuration. The bond distances of Pd-N [2.061 (2) Å] and Pd-Cl [2.302 (3) Å] are comparable with the values found in related complexes (Chen et al., 2002;Newkome et al., 1982). The dihedral angle between the aromatic ring plane and the square plane around Pd1 is 70.54 (2)°. Intermolecular N-H···Cl hydrogen bonds involving the amino groups and chlorine anions (Table 1) lead to a chain along [100] (Fig. 2). These chains are further self-assembled into a three-dimensional network through N-H···O and N-H···Cl hydrogen bonds (Fig. 3).

Experimental
A mixture of palladium chloride (0.1 mmol, 0.018 g) and 4-nitroaniline (0.2 mmol, 0.027 g) in 10 ml of anhydrous ethanol was sealed in an autoclave equipped with a Teflon liner (23 ml) and then heated at 353 K for 2 days. Yellow crystals were obtained by slow evaporation of the solvent at room temperature (yield: 49% based on 4-nitroaniline).

Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93 and N-H = 0.90 Å and with U iso (H) = 1.2U eq (C,N). The hightest peak is located 0.99 Å from Pd1 and the deepest hole is located 1.24 Å from H5.  The molecular structure of the title compound, showing 30% probability displacement ellipsoids.