Hexaaquacobalt(II) 2,2′-[naphthalene-1,8-diylbis(oxy)]diacetate dihydrate

In the title compound, [Co(H2O)6](C14H10O6)·2H2O, the 2,2′-[naphthalene-1,8-diylbis(oxy)]diacetate dianion L is not coordinated to the CoII ion. The asymmetric unit contains half of the L dianion, half of a [Co(H2O)6]2+ cation (both molecules being completed by inversion symmetry), and one water molecule. The crystal packing features O—H⋯O hydrogen bonding between the carboxylate groups, the aqua ligands and the hydrate water molecules.

In the title compound, [Co(H 2 O) 6 ](C 14 H 10 O 6 )Á2H 2 O, the 2,2 0 -[naphthalene-1,8-diylbis(oxy)]diacetate dianion L is not coordinated to the Co II ion. The asymmetric unit contains half of the L dianion, half of a [Co(H 2 O) 6 ] 2+ cation (both molecules being completed by inversion symmetry), and one water molecule. The crystal packing features O-HÁ Á ÁO hydrogen bonding between the carboxylate groups, the aqua ligands and the hydrate water molecules.
The asymmetric unit of the complex consists of a half ligand L, a half Co II ion complexed with three water molecules and one additional water molecule. The Co II center is octahedrally coordinated by six water molecules. The two carboxylate arms of the LH2 ligand lie in the same plane as the naphthalene ring. The hydrogen atoms of the water molecular and the oxygen atoms which are coordinated by Co II are involved in hydrogen bonding with the oxygen atoms of the carboxylate group (Table 2, Fig. 2). In this case a sheet-like structure is formed.

Experimental
The ligand LH2 was synthesized according to the procedure published by Mondal et al. (2008).
A mixture of Co(NO 3 ) 2 .6H 2 O (0.05 mmol, 0.015 g), L (0.05 mmol, 0.013 g), water (1 ml) and DMF (1 ml) was heated at 393 K in a Teflon-lined autoclave for three days, followed by slow cooling to room temperature. The resulting pink block crystals were filtered off and washed with distilled water.

Refinement
The H atoms on the ligands were positioned geometrically and refined as riding [C-H = 0.93 Å and U iso (H) = 1.2U eq (C)].
Hydrogen atoms of the water molecules were located in the Fourier difference maps and refined with restraints for the O-H distances and H-O-H angles.

Figure 2
Three dimensional supramolecular architecture constructed by intermolecular hydrogen bonds. The dotted lines indicate the hydrogen bonds. 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.