Pentane-1,5-diammonium tetrachloridopalladate(II)

In the title compound, [NH3(CH2)5NH3][PdCl4], the square-planar [PdCl4]2− anions are centrosymmetric while the diammonium cation lies in a general position. In addition to electrostatic interactions, the two species are linked through N—H⋯Cl hydrogen bonds to form a three-dimensional network.

In the title compound, [NH 3 (CH 2 ) 5 NH 3 ][PdCl 4 ], the squareplanar [PdCl 4 ] 2À anions are centrosymmetric while the diammonium cation lies in a general position. In addition to electrostatic interactions, the two species are linked through N-HÁ Á ÁCl hydrogen bonds to form a three-dimensional network.
Dr Jean Michel Leger is acknowledged for assistance during a preliminary investigation.

Comment
Extensive studies have been carried out on the crystal structures, phase transitions and physical properties of two-dimensional perovskite-like compounds of the families (C n H 2n+1 NH 3 ) 2 MX 4 and [NH 3 -(CH 2 ) n -NH 3 ]MX 4 , where X represents a halogen atom and M is a divalent metal. A few tetrachloropalladate compounds of these families have been structurally (Berg & Søtofte, 1976) and (Maris et al., 1996). We report here the crystal structure, determined at room temperature, of the title palladium-chloride compound [NH 3 -(CH 2 ) 5 -NH 3 ][PdCl 4 ] (I).
The asymmetric unit of (I) contains one cation in general position and two distinct half [PdCl 4 ] 2− units (Fig. 1). The Pd atoms lie on inversion centers and display a square-planar coordination environment with four Cl − ligands. The Pd-Cl distances range from 2.3129 (4) to 2.3207 (6) Å (Table 1). The [PdCl 4 ] moieties pack via longer Pd-Cl contacts (3.0244 (9) and 3.1788 (9) Å) to form puckered two-dimensional layers in the (a,b) plane. The cations are located between these layers and the whole crystallographic organization can be described as a succession of organic and inorganic layers. The diammonium chain adopts a left-handed conformation at one end with a terminal C-C-C-N torsion angles of 67.86 (12)°.
The whole chain makes an angle of 83.55 (3)° with the palladium layer.
The link between the two moieties and the crystal packing is achieved by several hydrogen bonds involving the H atoms of the ammonium groups and the Cl atoms. The three shortest hydrogen bonds (Fig. 2) show a pattern similar to the hydrogen bond scheme found in the tetrachloro and tetrabromocuprate(II) analogues. (Garland et al. 1990). Additional contacts (Table   2) with longer hydrogen chlorine distances and more acute N-H···Cl angles are also present.

Experimental
Crystals for X-ray structural analysis were grown by slow evaporation at room temperature of a saturated aqueous solution obtained by dissolving PdCl 2 (0.2 g, 1.12 mmol) and NH 2 (CH 2 ) 5 NH 2 (0.12 g, 1.12 mmol) in an excess of concentrated HCl.

Refinement
H atoms of the carbon chain skeleton were positioned geometrically and refined using a riding model with U iso (H) values of 1.2U eq (C). H atoms of the ammonium groups were located from difference Fourier map and refined as riding atoms with U iso (H) values of 1.5U eq (N).

Special details
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 > 2σ(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.