Catena(hexa-aqua-cobalt(ii) tetra-aqua-(μ2-1,2,4,5-benzenecarboxylato-o,o’) -cobalt(ii) hydrate): a new symmetry for an old polymorphic phase

Abstract

The title cobalt complex (C10H38Co2O26) consists of [Co(H2O)4(C10H2O8)]2-n anionic chains, balanced by [(Co(H2O)6]2+ cations and eight solvato water molecules, some of which are disordered. The chains are formed by Co(H2O)4 “beads” threaded by fully deprotonated benzenecarboxylato anions binding in a stretched, trans fashion, and they are linked by H-bonds into a 2D structure. The cationic groups and solvato water molecules form a second kind of 2D arrays, “sanwiched” by the latter ones and linking the lot into a 3D structure through a very complex H-bonding interaction scheme. The structure presents a very conspicuous pseudo symmetry, and it appears to be a slight polymorphic modification of an already published isologue of identical formulation but with the higher symmetry properly attained, in a volume half as large. The slight differences between both structures seems to reside mainly in the (disordered) solvates, as suggested by the overlap of both models.