Combination of Lacunary Polyoxometalates and High-Nuclear Transition Metal Clusters under Hydrothermal Conditions: IX. A Series of Novel Polyoxotungstates Sandwiched by Octa-Copper Clusters

The reaction of CuCl2 center dot 2H(2)O with trivacant Keggin polyoxoanions K8Na2[A-alpha-GeW9O34]center dot 25 H2O or K-10[A-alpha-SiW9O34]center dot 25H(2)O in the presence of 1,2-diaminopropane (dap), ethylenediamine (en) or 2,2'-bipyridine (2,2'-bpy) under hydrothermal conditions afforded five novel hybrid inorganic-organic octa-Cu sandwiched polyoxotungstates (POTs): H-4[Cu-8(II)(dap)(4)(H2O)(2)(B-alpha-Ge-W9O34)(2)]center dot 13 H2O (1), (H(2)en)(2)[CU8II- (en)(4)(H2O)(2)(B-alpha-GeW9O34)(2)]center dot 5H(2)O(2), (H(2)en)(2)[Cu-8(II)(en)(4)(H2O)(2)(B-alpha-SiW9O34)(2)]center dot 8H(2)O (3), [Cu-II(H2O)(2)]H-2[CU8II (en)(4)(H2O)(2)(B-alpha-SiW9O34)(2)] (4), and [CU2II(H2O)(2)(2,2'-bpy)(2)]{[Cu-II(bdyl)](2)- [Cu-8(II)(2,2'-bpy)(4)(H2O)(2)(B-alpha-GeW9O34)(2)]}center dot 4H(2)O (bdyl = 2,2'-bipyridinyl)(5). Additionally, CUCl2 center dot 2H(2)O reacts with the mixture of GeO2, Na2WO4 center dot 2H(2)O, H2SiW12O40 center dot 2H(2)O in the presence of 2,2'-bpy and 4,4'-bpy under hydrothermal conditions leading to another novel mixed-valent octa-Cu sandwiched POT hybrid: [Cu-I(2,2'-bpy) (4,4'-bpy)](2)[{CU2I(2,2'-bpy)(2)(4,4'bpy)(2)[(CU2CU6II)-C-I(2,2'-bpy)(2)(4,4'-bpy)(2)(B- alpha-GeW9O34)(2)}]center dot 2H(2)O (6). 1, 2, and 3 are discrete dimers constructed from two trivacant Keggin [B-alpha-XW9O34](10-)(X=Ge-IV/Si-IV) fragments and an octa Cu cluster whereas 4 displays the 3D (3,6)-connected nets with (4.6(2))- (4(2).6(4).8(7).10(2)) topology, which are built by octa-Cu sandwiched polyoxometalate building blocks through copper cation bridges. 5 is a novel 2D layer based on octa-Cu sandwiched POT clusters and [CU2II(bdyl)] units. Interestingly, the rollover metalation of 2,2'-bpy is firstly observed in the system containing the copper complex under hydrothermal conditions. 6 is a discrete mixed-valent octa-Cu sandwiched POT supported by two Cu-I-complexes [CU2I(2,2'-bpy)(2)(4,4'-bpy)](2+) through 4,4'-bpy bridges, which constructs a novel dodeca-copper cluster. Notably, the octa-Cu cluster in 6 is mixed-valent and is different from those in 1-5. To our knowledge, 1-6 represent a rare family of POTs incorporating novel octa-nuclear transition-metal clusters in polyoxometalate chemistry. They were structurally characterized by FF-IR spectra, elemental analysis, thermogravimetric analysis, and single-crystal Xray diffraction. The magnetic properties of 1, 4, and 5 were quantitatively analyzed by the MAGPACK software package.