Acta Cryst. (2008). E64, m538-m539  [ doi:10.1107/S1600536808006715 ]

cyclo-Tetra--malato-¹⁶O,O',O'':O'''-tetrakis[bis(1H-benzimidazole-N³)cobalt(II)] eicosahydrate

J.-H. Li, J.-J. Nie, J.-R. Su and D.-J. Xu

Abstract: The title compound, [Co₄(C₄H₄O₅)₄(C₇H₆N₂)₈]·20H₂O, consists of tetranuclear Co^II complexes and disordered uncoordinated water molecules. The tetrameric complex molecule has symmetry. While two benzimidazole molecules and a tridentate malate dianion coordinate a Co^II ion, the carboxylate O atom from an adjacent malate dianion bridges the Co^II ions to complete a distorted octahedral coordination geometry. The tridentate malate dianion chelates the Co^II ion, and the chelate six- and five-membered rings show half-chair and envelope configurations, respectively. A face-to-face separation of 3.494 (9) Å between parallel benzimidazole ligands indicates the existence of - stacking between adjacent complexes. The crystal structure also involves N-HO and O-HO hydrogen bonds.

Online 14 March 2008

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