Hydrothermal syntheses and structural characterization of two sandwich-type arsenotungstates

Two new organic-inorganic composite sandwich-type arsenotungstates [H2dap]6H8[Ni4(H2O)2(B--AsW9O34)2]2 center dot 33H2O (1) and {[Ni(dap)2(H2O)]2[Ni(dap)2]2[Ni4(Hdap)2(B--AsW9O34)2]} center dot 4H2O (2) (dap = 1,2-diaminopropane) have been hydrothermally synthesized by reaction of Na8[A--HAsW9O34] center dot 11H2O with NiCl2 center dot 6H2O in the presence of 1,2-diaminopropane and characterized by elemental analysis, IR spectra, X-ray single-crystal diffraction, and thermogravimetric analysis. 1 crystallizes in the triclinic P1 space group with a = 16.351(6) angstrom, b = 16.423(6) angstrom, c = 19.894(7) angstrom, = 110.630(6)degrees, = 92.684(7)degrees, =104.946(7)degrees, V = 4774(3) angstrom 3, Z = 1, GOOF = 1.033, R1 = 0.0517, wR2 = 0.1086. 2 also crystallizes in the triclinic P1 space group with a = 13.305(4) angstrom, b = 13.882(4) angstrom, c = 17.031(5) angstrom, = 68.109(5)degrees, = 71.511(4)degrees, = 88.407(5)degrees, V = 2753.5(14) angstrom 3, Z = 1, GOOF = 1.051, R1 = 0.0491, wR2 = 0.1150. Notably, 1 is a discrete structure, composed of two tetra-NiII substituted sandwich-type polyoxoanions [Ni4(H2O)2(B--AsW9O34)2]10- with different spatial orientation, whereas 2 displays a organic-inorganic composite 2-D sheet architecture constructed by tetra-NiII sandwiched [Ni4(H2O)2(B--AsW9O34)2]10- units by means of [Ni(dap)2]2+ bridges. Some previously reported transition-metal-substituted sandwich-type polyoxotungstates have been summarized.