Poly[μ-aqua-aqua-μ4-naphthalene-1,8-dicarboxylato-barium]: a layer structure

The title compound, [Ba(C12H6O4)(H2O)2]n, is represented by a layer-like structure built of BaO8 polyhedra. The asymmetric unit contains a Ba2+ ion, half a coordinating water molecule and half a μ4-bridging naphthalene-1,8-dicarboxylate (1,8-nap) ligand, the whole structure being generated by twofold rotational symmetry. The carboxylate groups of the 1,8-nap ligands act as bridges linking four Ba2+ ions, while each Ba2+ ion is eight-coordinated by O atoms from four 1,8-nap ligands and two coordinating water molecules. In the crystal, there are O—H⋯O hydrogen bonds involving the water molecules and carboxylate O atoms in the BaO8 polyhedra. Each BaO8 polyhedron is connected via corner-sharing water O atoms or edge-sharing ligand O atoms, forming a sheet parallel to the bc plane. These sheets stack along the a-axis direction and are connected via van der Waals forces only. The naphthalene groups protrude above and below the layers of the BaO8 polyhedra and there are voids of ca 208 Å3 bounded by these groups. No residual electron density was found in this region. The crystal studied was twinned by pseudo-merohedry, with a refined twin component ratio of 0.5261 (1):0.4739 (1).

The title compound, [Ba(C 12 H 6 O 4 )(H 2 O) 2 ] n , is represented by a layer-like structure built of BaO 8 polyhedra. The asymmetric unit contains a Ba 2+ ion, half a coordinating water molecule and half a 4 -bridging naphthalene-1, 8-dicarboxylate (1,8nap) ligand, the whole structure being generated by twofold rotational symmetry. The carboxylate groups of the 1,8-nap ligands act as bridges linking four Ba 2+ ions, while each Ba 2+ ion is eight-coordinated by O atoms from four 1,8-nap ligands and two coordinating water molecules. In the crystal, there are O-HÁ Á ÁO hydrogen bonds involving the water molecules and carboxylate O atoms in the BaO 8 polyhedra. Each BaO 8 polyhedron is connected via corner-sharing water O atoms or edge-sharing ligand O atoms, forming a sheet parallel to the bc plane. These sheets stack along the a-axis direction and are connected via van der Waals forces only. The naphthalene groups protrude above and below the layers of the BaO 8 polyhedra and there are voids of ca 208 Å 3 bounded by these groups. No residual electron density was found in this region. The crystal studied was twinned by pseudo-merohedry, with a refined twin component ratio of 0.5261 (1):0.4739 (1).
(1,8-nap) has been used extensively to construct a number of metal organic complexes (Wen et al., 2007(Wen et al., ,2008Zhang et al., 2008), including the related barium compound Ba(C 12 H 6 O 4 ) [Fu et al., 2011]. To prepare a new barium complex incorporating 1,8-nap ligand, we have synthesized the title compound and report herein on its crystal structure.
The title compound is a non-interpenetrating two-dimensional layer-like structure consisting of BaO 8 clusters, which are similar to the reported compound Ba(C 12 H 6 O 4 ) [Fu et al., 2011]. As shown in Fig Furthermore, each BaO 8 polyhedra is connected via corner-sharing H 2 O oxygen atoms or edge-sharing ligand oxygen atoms to form a two-dimensional sheet parallel to the bc plane. All Ba atoms in the two-dimensional layer are coplanar, with adjacent Ba···Ba distance of 4.4821 (6), 4.9292 (6) and 5.0972 (6) Å.
By considering the Ba atoms as the nodes, this two-dimensional layered structure can be topologically represented as a 6-connected (3,6) net.
In the crystal, there are O-H···O hydrogen bonds involving the water molecules and the carboxylate O atoms in the BaO 8 clusters (Fig. 2 and Table 1). There are no π-π stacking interactions, only van der Waals forces are present between the layers that stack along the a direction. The naphthalene groups protrude above and below the layers of the BaO 8 clusters and there are voids of ca. 208 Å 3 bounded by these groups. No residual electron density was found in this region.

Experimental
A mixture of naphthalene-1,8-dicarboxylic (0.2 g), BaCO 3 (0.05 g) and H 2 O (15 ml) was heated at 443 K for 3 d in a sealed 25 ml Teflon-lined stainless steel vessel under autogenous pressure. After cooling to room temperature at a rate of 20°C h -1 , colourless prismatic crystals suitable for single-crystal X-ray diffraction analysis were obtained in low yield.

Poly[µ-aqua-aqua-µ 4 -naphthalene-1,8-dicarboxylato-barium]
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.54 e Å −3 Δρ min = −0.57 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.