A three-dimensional coordination polymer,[Ni（Hbyip2-）（bix）0.5（H2O）]n,has been hydrothermally synthesized.Each Ni2＋ ion is five-coordinated by three carboxylate O atoms from three different 5-（benzoic acid-4-yldiazenyl）isophthalate（Hbyip2-） anions,one N atom from one 1,4-bis（imidazol-1-ylmethyl）benzene（bix） ligand and one O atom from an aqua ligand displaying a distorted square-pyramid.Each Ni atom is defined by three Hbyip2-anions and each Hbyip2-anion adopts a tris（mono-dentate） ligand coordinating to three Ni2＋ ions affording a 36-membered inorganic ring.These rings are further arranged into an undulated two-dimensional layer parallel to the（101） plane.Adjacent two-dimensional networks are linked by bix ligands into a three-dimensional {63,83}{63} framework with a large channel（ca.26.3 × 13.6） along the [100] direction.Each individual {63,83}{63} network interpenetrates with two others in a parallel fashion to generate a 3-fold interpenetrating network.
A new organic-inorganic hybrid sandwich-type arsenotungstate[H2dap]2H2[Ni（dap）2] [Ni（dap）2（H2O）2][Ni4（H2O）2（B-α-AsVW9O34）2]·8H2O 1 （dap = 1,2-diaminopropane） has been synthesized by the reaction of Na6[AsIII2W21O69（H2O）]·nH2O, NiCl2·6H2O and dap under hydrothermal conditions and structurally characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. 1 crystallizes in the monoclinic space group P21/n with a = 13.5133（19）, b = 19.043（3）, c = 17.647（2）, β = 102.585（2）°, V = 4432.0（11） 3, T = 296（2） K, Z = 2, μ = 25.350 mm–1, GOOF = 1.058, R = 0.0353 and wR = 0.0838. The molecular unit of 1 consists of two diprotonated [H2dap]2＋ cations, two protons, one four-coordinate [Ni（dap）2]2＋ cation, one six-coordinate [Ni（dap）2（H2O）2]2＋ cation, one classic tetra-NiII substituted sandwich-type [Ni4（H2O）2（B-α-AsVW9O34）2]10– polyoxoanion and eight lattice water molecules. Furthermore, some reported different types of transition-metal substituted sandwich-type polyoxoanions are summarized and compared.
