Poly[[μ10-4,4′-(ethane-1,2-diyldioxy)dibenzoato]dipotassium]

The title salt, [K2(C16H12O6)]n, was obtained by the reaction of 1,2-bis[4-(ethyl-carboxyl)-phenoxyl]ethane with KOH in water. The anion lies on a crystallographic inversion center, which is located at the mid-point of the central C—C bond. The K+ cation is coordinated by six O atoms, two from the chelating carboxylate group of the anion and four from four neighboring and monodentately binding anions, giving rise to an irregular [KO6] coordination polyhedron. The coordination mode of the cation leads to the formation of K/O layers parallel to (100). These layers are linked by the nearly coplanar anions (r.m.s. deviation of 0.064 Å of the carboxyl, aryl and O—CH2 groups from the least-squares plane) into a three-dimentional network.

The title salt, [K 2 (C 16 H 12 O 6 )] n , was obtained by the reaction of 1,2-bis[4-(ethyl-carboxyl)-phenoxyl]ethane with KOH in water. The anion lies on a crystallographic inversion center, which is located at the mid-point of the central C-C bond. The K + cation is coordinated by six O atoms, two from the chelating carboxylate group of the anion and four from four neighboring and monodentately binding anions, giving rise to an irregular [KO 6 ] coordination polyhedron. The coordination mode of the cation leads to the formation of K/O layers parallel to (100). These layers are linked by the nearly coplanar anions (r.m.s. deviation of 0.064 Å of the carboxyl, aryl and O-CH 2 groups from the least-squares plane) into a three-dimentional network.
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010 The coordination chemistry of carboxylic compounds is attracting current attention, based on interesting properties like gas adsorption and separation, catalysis, magnetism, luminescence and host-guest chemistry (Su et al., 2010;Zhu et al., 2008) of these compounds. It is well-known that carboxylic acids are excellent building blocks for the construction of coordination polymers, yielding extended frameworks by virtue of their bridging abilities (Ma et al., 2005;Zhang & Chen, 2008). Hence, the present paper aims to promote the search for new metal carboxylic complexes exhibiting special properties in many fields, in particular those bearing multicarboxylic-type ligands, a promising but still rather underdeveloped field of research. We report here the structure of a new polymeric dipotassium dicarboxylic compound ( Fig. 1).
In the asymmetric unit one half of the anion is present. The anion lies on a crystallographic inversion center, which is located at the mid point of the C8-C8 i bond (symmetry code (i) = -x-1, -y-1, -z). All bond lengths and angles of the anion are within normal ranges (Allen et al., 1987). The K + ion is coordinated by six oxygen atoms, two from the ligand and four from neighboring ligands, in a distorted [KO 6 ] polyhedron (Fig 2), whereby one anion coordinates all in all to ten K + cations. The benzene rings of the anion are parallel to each other with a plane-to-plane distance of 3.488 Å. The carboxyl, aryl and O-CH 2 moieties are coplanar with an r.m.s. deviation of 0.0638 Å.
A three-dimensional network is spanned owing to the coordination mode of the potassium cations. The K + cations and the O atoms of the carboxylate anions form a layer parallel to (100). These layers are finally connected by the substituted ethane moieties into a three-dimensional structure (Fig. 2).

Experimental
The precusor of the title compound was prepared by a reported procedure (Ma & Yang, 2011). The title compound was synthesized by the reaction of the precusor, diethyl 4,4′-(ethane-1,2-diyldioxy)-dibenzoate and potassium hydroxide in the conditions as follows: The precusor (1.0 g, 2.8 mM) and KOH (0.31 g, 5.6 mM) were put in water (150 cm 3 ) in a 250 cm 3 flask and the system was stirred for 24 h at 373 K for all solids dissolved and cooled down to room temperature.
After filtration, a colorless solution was obtained. Evaporation of the solution gave a white solid (0.82 g, 77 %), which was washed with ethanol two times (10 ml each). Slow evaporation of a solution of the title compound in water led to the formation of colorless crystals, which were suitable for X-ray characterization.

Refinement
Hydrogen atoms bonded to the C atoms of the anion were positioned geometrically and refined using a riding model with C-H = 0.93 -0.97 Å and with Uiso(H) = 1.2 times Ueq(C). These hydrogen atoms were assigned isotropic thermal parameters and allowed to ride on their respective parent atoms.

Poly[[µ 10 -4,4′-(ethane-1,2-diyldioxy)dibenzoato]dipotassium]
Crystal data 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 > 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.