cyclo-Tetra-μ-malato-κ(16) O,O′,O′′:O′′′-tetra­kis[bis­(1H-benzimidazole-κN (3))cobalt(II)] eicosa­hydrate

The title compound, [Co(4)(C(4)H(4)O(5))(4)(C(7)H(6)N(2))(8)]·20H(2)O, consists of tetra­nuclear Co(II) complexes and disordered uncoordinated water mol­ecules. The tetra­meric complex mol­ecule has [Image: see text] 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 π–π stacking between adjacent complexes. The crystal structure also involves N—H⋯O and O—H⋯O hydrogen bonds.