| Summary: | The title compound, [Co4(C4H4O5)4(C7H6N2)8]·20H2O, consists of tetranuclear CoII complexes and disordered uncoordinated water molecules. The tetrameric complex molecule has overline{4} symmetry. While two benzimidazole molecules and a tridentate malate dianion coordinate a CoII ion, the carboxylate O atom from an adjacent malate dianion bridges the CoII ions to complete a distorted octahedral coordination geometry. The tridentate malate dianion chelates the CoII 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 π–π stacking between adjacent complexes. The crystal structure also involves N—H...O and O—H...O hydrogen bonds.
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