Poly[hexaaquabis(μ3-heptanedioato-κ3 O:O′:O′′)dimagnesium]

In the title compound, [Mg2(C7H10O4)2(H2O)6]n, the MgII ion is coordinated by three aqua ligands and three O atoms from three heptanedioato ligands in a distorted octahedral geometry. Each heptanedioato ligand bridges three Mg atoms, generating polymeric layers parallel to the bc plane. The polymeric layers related by translation along the a axis interact further via O—H⋯O hydrogen bonds, which consolidate the crystal packing.

In the title compound, [Mg 2 (C 7 H 10 O 4 ) 2 (H 2 O) 6 ] n , the Mg II ion is coordinated by three aqua ligands and three O atoms from three heptanedioato ligands in a distorted octahedral geometry. Each heptanedioato ligand bridges three Mg atoms, generating polymeric layers parallel to the bc plane. The polymeric layers related by translation along the a axis interact further via O-HÁ Á ÁO hydrogen bonds, which consolidate the crystal packing.
Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97. This project was supported by the Scientific Research Fund of Ningbo University (grant No. XKL069) and the Education Department of Zhejiang Province. Grateful thanks are also extended to the K. C. Wong Magna Fund in Ningbo University.

Comment
The past decade has witnessed enormous expansion of research on robust microporous coordination polymers (Borkowski et al., 2006;Dimos et al., 2002;Kim et al., 2001). For such purpose, design and synthesis of novel coordination polymers have been focused on organic ligands, others have reported lists of complexs used dicarboxylic acids. In this contribution, we report the crystal structure of the title compound (I).
In (I) (  (Liu et al., 2009). The Mg 2+ ions are bridged by the pimelate anions, forming the polymeric layers parallel to (100) (Fig. 2). When the Mg atom and the pim 2anions are treated as 3nodes, the two-dimensional layers can be best described as (4.8 2 ) topological network. Intermolecular O-H···O hydrogen bonds (Table 1) between the aqua ligand and carboxylate oxygen atoms make a contribution to stabilization of the three-dimensional framework.

Experimental
Dropwise addition of 1 M NaOH (1.0 ml) to a stirred aqueous solution of (0.1248 g, 0.5 mmol) MgSO 4 .7H 2 O in 5.0 ml H 2 O produced pale-white Mg(OH) 2 .xH 2 O precipitate, which was separated by centrifugation and washed with distilled water several times until no detectable SO 4 2anions in the supernatant. Subsequently, the 0.0815 g (0.5 mmol) pimelic acid was dissolved completely with 15 ml H 2 O, and then the precipitate was added. The resulting mixture was further stirred for 30 min and then filtered. The white filtrate (pH = 5.70) was allowed to stand at room temperature. Slow evaporation for several days afforded colourless platelet-like crystals.