An organic–inorganic hybrid nickel-substituted arsenotungstate consisting of three types of polyoxotungstate units

A new organic–inorganic hybrid nickel-substituted arsenotungstate [Na(H2O)3]2[Ni(H2O)6]2[Ni(H2O)5]{[Ni3(dap)(H2O)2]2(H2W4O16)}{(α-H2AsW6O26)[Ni6(OH)2(H2O)(dap)2](B-α-HAsW9O34)}2·7H2O (1) (dap = 1,2-diaminopropane) has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Crystal data for 1: C18H144As4N12Na2Ni21O176W34, Mr = 11174.92, triclinic, space group P-1, a = 15.004(4) Å, b = 16.357(5) Å, c = 22.070(6) Å, α = 80.458(5)°, β = 79.291(5)°, γ = 72.074(5)°, V = 5030(3) Å3, Z = 1, GOOF = 1.007, R1 = 0.0703, wR2 = 0.1670. The skeleton of 1 is a centric nanoscale cluster and is composed of two asymmetric sandwich-type clusters {(α-H2AsW6O26)[Ni6(OH)2(H2O)(dap)2](B-α-AsW9O34)}7− linked by a symmetric cluster {[Ni3(dap)(H2O)2]2(H2W4O16)}6+. Notably, 1 is an interesting polyoxometalate containing the trivacant Keggin [B-α-AsW9O34]9−, hexavacant Keggin [α-AsW6O26]11− and tetrameric [W4O16]8− units. Magnetic measurements indicate that 1 shows the ferromagnetic interactions within NiII centers.