Crystal structure of a new hydrate form of the NSAID sodium diclofenac.

The crystal structure is reported of sodium 2-[2-(2,6-di-chloro-anilino)phen-yl]acetate 3.5-hydrate or tetra-μ-aqua-κ :-deca-aqua-bis-{μ-2-[2-(2,6-di-chloro-anilino)phen-yl]acetato-κ ::}tetra-sodium(I) bis-{2-[2-(2,6-di-chloro-anil-ino)phen-yl]acetate}, {[Na(CHClNO)(HO)](CHClNO)} , which re-presents a new hydrate form of the NSAID sodium diclofenac (SD). The triclinic unit cell contains one ionic compound with formula Na(CHClNO)(HO), in which two symmetry-related carboxyl-ate anions CHClNO are bonded to a centrosymmetric [Na] core cationic cluster, while the others are only hydrogen bonded to the cationic cluster. The conformation for the anions is similar to that found in other diclofenac compounds, and the [Na(O)(HO)] cluster displays an unprecedented geometry, which can be described as an incomplete dicubane cluster formed by face-sharing incomplete cubes. A complex framework of O-H⋯O hydrogen bonds stabilizes the crystal structure. The herein reported crystal structure for SD·3.5HO in space group is different from those previously reported for other hydrates, namely SD·4.75HO (2) and SD·5HO (2/).