Diaquabis(5-fluoro-2-hydroxybenzoato-κO 1)zinc(II)

The title compound, [Zn(C7H4FO3)2(H2O)2], is a monomeric ZnII complex. The ZnII atom, which lies on a twofold rotation axis, is situated in a distorted tetrahedral environment composed of two monodentate carboxlyate O atoms and two water O atoms. O—H⋯O hydrogen bonds link these units, forming sheets that are stacked along the c axis.

The title compound, [Zn(C 7 H 4 FO 3 ) 2 (H 2 O) 2 ], is a monomeric Zn II complex. The Zn II atom, which lies on a twofold rotation axis, is situated in a distorted tetrahedral environment composed of two monodentate carboxlyate O atoms and two water O atoms. O-HÁ Á ÁO hydrogen bonds link these units, forming sheets that are stacked along the c axis.
Financial support from the National Science Foundation, awards CHE-0714555 and CHE-0714439, is gratefully acknowledged. Metal carboxylate complexes have long been an extensively studied class of compounds (Mehrotra & Bohra, 1983), and in recent years they have become a major focus of study due to their potentally useful properties (Janiak, 2003;Wasuke et al., 2005). As a continuation of our own studies (Ellsworth & zur Loye, 2008), we report here the crystal structure of the title compound.
The structure of the title compound is built from the monomeric complex of formula Zn(5-fsalcyl) 2 (H 2 O) 2 ( Fig. 1) (5-fsalcyl = 5-fluorosalicylate). The asymmetric unit consists of one Zn II atom that lies on a twofold rotation axis, one 5-fsalcyl ligand, and one water molecule. The coordination environment of the Zn II atom is that of a distorted tetrahedron consisting of two equivalent O atoms from two monodentate carboxylates, and two equivalent O atoms from two water molecules. All four Zn-O bond distances fall within the normal range, with an average length of 1.969 (2) Å. It is worth noting that for the carboxylate O2 atom, the Zn···O2 distance of 2.692 (2)Å falls outside the range considered normal for a Zn-O coordination bond (Wang et al., 2006).
Due to its monodentate binding mode, the 5-fsalcyl carboxylate group adopts a highly asymmetrical configuration. This is manifested in a C1-O1 distance [1.289 (3) Å] for the coordinating O atom that is noticeably longer than the C1-O2 distance [1.246 (3) Å] corresponding to the noncoordinating O atom. In addition, the carboxylate group of the 5-fsalcyl ligand is twisted with a dihedral angle of 9.7 (2) ° with respect to the phenyl ring. As is typical for salicylates, the hydroxyl group of 5-fsalcyl is internally hydrogen bonded to its carboxylate O1 that is located on the same side of the ligand (Brownless et al., 1999).
The monomeric units are hydrogen bonded into chains that are themselves hydrogen bonded into sheets that are stacked along the c axis (Fig. 2).

Experimental
All chemicals and solvents were purchased from commercial sources and used without further purification. 5-Fluorosalicylic acid (3 mmol) was added to 100 ml of water and subsequently brought to pH 6.5 by the addition of 3M NaOH with constant