Bis(2-amino-1,3-benzothiazol-3-ium) bis(7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylato)cadmate hexahydrate

In the structure of the title complex, (C7H7N2S)2[Cd(C8H8O5)2]·6H2O, the CdII atom is located on an inversion center and is O,O′,O′′-chelated by two symmetry-related 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylate ligands in a distorted octahedral geometry. The 2-aminobenzothiazolium cation links with the Cd complex anion via N—H⋯O hydrogen bonding. Extensive O—H⋯O and N—H⋯O hydrogen bonds involving lattice water molecules occur in the crystal structure.

In the structure of the title complex, (C 7 H 7 N 2 S) 2 -[Cd (C 8 H 8 O 5 ) 2 ]Á6H 2 O, the Cd II atom is located on an inversion center and is O,O 0 ,O 00 -chelated by two symmetry-related 7oxabicyclo[2.2.1]heptane-2,3-dicarboxylate ligands in a distorted octahedral geometry. The 2-aminobenzothiazolium cation links with the Cd complex anion via N-HÁ Á ÁO hydrogen bonding. Extensive O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds involving lattice water molecules occur in the crystal structure.

Experimental
A mixture of 0.5 mmol norcantharidin, 0.5 mmol cadmium acetate, 0.5 mmol 2-aminobenzothiazole and 15 mL distilled water was sealed in a 25 mL Teflon-lined stainless vessel and heated at 443 K for 3 d, then slowly cooled to room temperature. The solution was filtered and block-shaped colorless crystals were obtained.

Refinement
The H atoms bonded to O atoms were located in a difference Fourier maps, repositionned to a correct geometry and subsequently refined using a riding model and allowed to rotate around the pivot oxygen atom (AFIX 6 in SHELXL).
The isotropic ADP of the water hydrogen atoms were set as follows: U iso (H) = 1.5U eq (O). Other H atoms were positioned geometrically and refined using a riding model with C-H = 0.97-0.98 and N-H = 0.86 Å, U iso (H) = 1.2U eq (C,N).  A view of the molecule of (I) showing the atom-labelling scheme with displacement ellipsoids drawn at the 30% probability.

Bis(2-amino-1,3-benzothiazol-3-ium) bis(7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylato)cadmate hexahydrate
Crystal data Hall symbol: -P 1 a = 6.6990 (8) Å b = 10.3103 (10) Å c = 13.0979 (13) Å α = 89.039 (7) Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.