Diaqua(1,4,8,11-tetraazacyclotetradecane)nickel(II) fumarate tetrahydrate

The asymmetric unit of the title complex salt, [Ni(C10H24N4)(H2O)2](C4H2O4)·4H2O, comprises half of a nickel(II) complex dication, half of a fumarate dianion and two water molecules. Both the NiII cation and fumarate anion lie on a crystallographic inversion center. The NiII ion in the cyclam complex is six-coordinated within a distorted N4O2 octahedral geometry, with the four cyclam N atoms in the equatorial plane and the two water molecules in apical positions. The six-membered metalla ring adopts a chair conformation, whereas the five-membered ring exists in a twisted form. In the crystal packing, intermolecular O—H...O hydrogen bonds between the water molecules and the carboxyl groups of the fumarate anions lead to the formation of layers with R42(8) ring motifs. NiII complex cations are sandwiched between two such layers, being held in place by O—H...O, N—H...O and C—H...O hydrogen bonds, consolidating a three-dimensional network.