Poly[(μ2-1,3-di-4-pyridylpropane)(μ3-1,3-phenylenediacetato)cadmium]

In the title compound, [Cd(C10H8O4)(C13H14N2)]n, two symmetry-related Cd atoms are bridged by two carboxylate O atoms into a binuclear Cd2 subunit around an inversion center. The Cd atom has a distorted pentagonal–bipyramidal environment, defined by five O atoms from three different 1,3-phenylendiacetate (1,3-pda) ligands and two N atoms from two 1,3-di-4-pyridylpropane (bpp) ligands. Each Cd2 subunit is linked to four different Cd2 subunits by four 1,3-pda ligands and four bpp ligands, forming a two-dimensional network with rhombic grids (12.50 × 12.50 Å2) extending along the ab plane.


Related literature
For a coordination polymer with a similar structure, see: Nagaraja et al. (2010). For another compound synthesized from the same components as the title compound, see: Zhang et al. (2009). For Cd-O and Cd-N bond lengths in related structures, see: Clegg et al. (1995); Tao et al. (2000).

Comment
In view of progress of crystal engineering, the appropriate choice of metal ions and organic building blocks is the most effective and facile method to assemble metal-organic compounds with various structures (Clegg et al., 1995;Nagaraja et al., 2010;Tao et al., 2000). In the past decade, rigid dicaboxylate and dipyridyl ligands have been widely employed as organic linkers to afford coordination polymers (Tao et al., 2000). Recently, flexible dicaboxylate and dipyridyl ligands have also been used to bond with metal ions (Nagaraja et al., 2010). And the complexes assembled by flexible ligands usually exhibit different structures with those of the complexes assembled by rigid ligands. In this work, we employed Cd(NO 3 ) 2 and two flexible ligands (1,3-phenylendiacetic acid, 1,3-pda, and 1,3-di-4-pyridylpropane, bpp) as our system and obtained the title compound.
As shown in Fig. 1, the symmetry-unique Cd atom is located in a pentagonal-bipyramidal environment, coordinated by five O atoms from three different 1,3-pda ligands at the equatorial sites and two N atoms from two bpp ligands at the axial sites. The Cd1-O [2.302 (3)-2.662 (3) Å] and Cd-N [2.319 (4)-2.320 (4) Å] distances are consistent with those previously observed in the related reported complexes (Clegg et al., 1995;Tao et al., 2000). Two symmetry related Cd atoms (Cd1 and Cd1 i ; symmetry code: (i) -x + 1, -y, -z) are bridged by two carboxylate O atoms into a binuclear Cd 2 subunit around an inversion center. Each Cd 2 subunit is linked to four different Cd 2 subunits by four 1,3-pda ligands and four bpp ligands forming a two-dimensional (4,4) network with rhombic grids (12.50 × 12.50 Å 2 ) extending along the ab plane (Fig. 2).
It should be noted that the complex [Cd 2 (1,3-pda) 2 (bpp) 3 ] n (Zhang et al., 2009) was synthesized from the same components as the title compound. However, its structure is completely different.

Experimental
4H 2 O (31 mg, 0.1 mmol), 1,3-phenylenediacetic acid (19 mg, 0.1 mmol), 1,3-di-4-pyridylpropane (20 mg, 0.1 mmol), 1.5 ml of H 2 O and 1.5 mL of EtOH were loaded to a 10 mL Pyrex glass tube. The tube was sealed and heated in an oven to 438 K for three days, and then cooled to ambient temperature at a rate of 5 K/h to form colourless blocks of the title compound, which were washed with ethanol and dried in air. Yield: 39 mg (78% yield based on Cd). Anal. calcd.

Refinement
All H atoms were placed in geometrically idealized positions (C-H = 0.94 Å for phenyl/pyridyl groups and C-H = 0.98 Å for methylene groups) and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C). Fig. 1. Coordination environment of Cd(II) in the title compound with nonhydrogen atoms represented by thermal ellipsoids at 30% probability level, hydrogen atoms are drawn as spheres of arbitrary radius. [Symmetry codes:

Figures
Crystal data [Cd(C 10