trans-Bis(2-acetamido-5-methylbenzoato-κO 1)tetraaquazinc

In the title compound, [Zn(C10H10NO3)2(H2O)4], the ZnII atom lies on a crystallographic inversion center and is six-coordinated by two monodentate trans-related 2-(N-acetylamino)-5-methylbenzoato ligands and four water molecules, giving a slightly distorted octahedral geometry. There are two intramolecular hydrogen bonds [amine N—H⋯Ocarboxyl and water O—H⋯Ocarboxyl], while extensive intermolecular water O—H⋯O hydrogen-bonding interactions extend the complex units into a two-dimensional network structure along (100).

In the title compound, [Zn(C 10 H 10 NO 3 ) 2 (H 2 O) 4 ], the Zn II atom lies on a crystallographic inversion center and is sixcoordinated by two monodentate trans-related 2-(N-acetylamino)-5-methylbenzoato ligands and four water molecules, giving a slightly distorted octahedral geometry. There are two intramolecular hydrogen bonds [amine N-HÁ Á ÁO carboxyl and water O-HÁ Á ÁO carboxyl ], while extensive intermolecular water O-HÁ Á ÁO hydrogen-bonding interactions extend the complex units into a two-dimensional network structure along (100).

Related literature
The study of metal coordination polymers has enhanced our understanding of the relationship between molecular structure and material function, see: Dai et al. (2005); Moulton & Zaworotko (2001).

Comment
In recent decades, the study of metal coordination polymers has witnessed tremendous growth as an attractive interface between synthetic chemistry and materials science, which significantly boosts the understanding of the relationship between molecular structure and material function (Moulton & Zaworotko, 2001;Dai et al., 2005). The crystal engineering of coordination polymers is highly influenced by the judicious choice of ligands, metal coordination geometry, template design and other subtle factors, such as counterions, solvent choice and reaction temperature. The deprotonated 2-(N-acetylamino)-5-methylbenzoic acid (HNB) ligands are good candidates in this respect for the construction of supramolecular architectures because in such bitopical ligands the N-acetyl group can act as a hydrogen-bond donor and/or acceptor, while the carboxyl function has strong coordination abilities with many metal ions. Taking these advantages into account, recently we have begun to assemble HNB and zinc ions into polymeric complexes under hydrothermal conditions. Herein, we report the synthesis and crystal structure of the title compound, [Zn(C 10 H 10 NO 3 ) 2 (H 2 O) 4 ] (I).
In the structure of (I) the Zn II metal center lies on a crystallographic inversion center. The local coordination environment around Zn II atom is slightly distorted octahedral, comprising two monodentate trans-related 2-(N-acetylamino)-5-methylbenzoato ligands and four water molecules (Fig. 1). Two intramolecular hydrogen bonds [amine N-H···O carboxyl and water O-H···O carboxyl ] stabilize the complex units while extensive intermolecular water O-H···O acetyl hydrogen-bonding interactions are observed in the structure (Table 1), giving rise to double-stranded chains. Further interactions involving the coordinated water ligands and the uncoordinated O atoms of the carboxyl group are gives a two-dimensional network structure (Fig. 2).

Refinement
H atoms attached to carbon and nitrogen were positioned geometrically and treated using a riding model, fixing the bond lengths at 0.86, 0.96 and 0.93 Å for NH, CH 2 and aromatic CH groups, respectively and U iso (H) = 1.2U eq (N, C)]. The aqua H atoms were located from difference maps and their coordinates refined but with U iso (H) = 1.5U eq (O).