Acta Cryst. (2008). E64, m1536-m1537 [ doi:10.1107/S1600536808036672 ]
Abstract: The title compound, [Ni(C4H2O4)(C10H8N2)2]·7.34H2O, was obtained by crystallization from an aqueous ethanolic reaction mixture containing nickel(II) acetate, maleic acid, bipyridine, sodium hydroxide and ammonia. The asymmetric unit contains one independent complex molecule and 7.34 water molecules occupying eight crystallographically independent positions. Two of these water molecules are disordered. The nickel(II) atom is coordinated in a distorted octahedral geometry by two O atoms from one carboxylate group of the maleato ligand and by four N atoms from two 2,2'-bipyridine (bipy) ligands. The water molecules, along with the O atoms of the uncoordinated carboxylate group, form an extended hydrophilic three-dimensional hydrogen-bonded system with large cavities in which the hydrophobic bipy ligands are located. One H atom of the maleate ligand is involved in a weak hydrogen bond of the C-HO type. Stacking interactions between the pyridyl rings of the bipy ligands [centroid-centroid distance = 3.549 (15) Å] lead to the formation of pairs of complex molecules.
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