title: Poly[diaqua-[μ-1,4-bis-(1H-imidazol-1-yl)benzene-κ(2)N(3):N(3')](μ-fumarato-κ(2)O(1):O(4))nickel(II)].
abstract: In the title compound, [Ni(C(4)H(2)O(4))(C(12)H(10)N(4))(H(2)O)(2)](n), the Ni(II) ion has a distorted octa-hedral coordination geometry. The asymmetric unit is composed of an Ni(2+) ion, located on a twofold rotation axis, one half of a 1,4-bis-(1H-imidazol-1-yl)benzene (BIMB) ligand and one half of a fumarte (fum(2-)) dianion, both ligands being located about inversion centers, and a coordinating water mol-ecule. The Ni(II) ions are linked by two BIMB ligands and two fum(2-) dianions, forming a four-connected layered structure parallel to (010) with a 4(4)-sql topology. Within each layer, there are rhombic grids with dimensions of ca 13.5 × 9.0 Å and approximate angles of 109 and 70°. The crystal packing features a two-dimensional → two-dimensional parallel/parallel interpenetration in which one undulating layer is catenated to another equivalent one, forming a new bilayer. Moreover, the entangled two-dimensional layers are connected by O-H⋯O and C-H⋯O hydrogen bonds, generating a three-dimensional structure.
authors.affiliation: College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070,  People's Republic of China.
authors.forename: Chang-Xin
authors.initials: CX
authors.lastname: Bian
authors.forename: Xiao-Qiang
authors.initials: XQ
authors.lastname: Yao
authors.forename: Yu-Min
authors.initials: YM
authors.lastname: Song