A combination of lacunary polyoxometalates and high-nuclear transition-metal clusters under hydrothermal conditions. part II: From double cluster, dimer, and tetramer to three-dimensional frameworks

The hydrothermal reactions of trivacant Keggin A-alpha-XW9O34 polyoxoanions (X=P-v/Si-IV) with transition-metal ions (Ni-II/Cu-II/Fe-II) in the presence of amines result in eight novel high-nuclear transition-metal-substituted polyoxotungstates [{Ni-7(mu(3)-OH)(3)O-2- (dap)(3)(H2O)(6)}(B-alpha-PW9O34)][{Ni-6(mu(3)-OH)(3)(dap)(3)(H2O)6}(B-alpha-PW9O34)][Ni- (dap)(2)(H2O)(2)]center dot 4.5H(2)O (1), [Cu(dap)-(H2O)(3)](2)[{Cu-8(dap)(4)(H2O)(2)}(B-alpha-SiW9- O-34)(2)]center dot 6H(2)O (2), (enH(2))(3)H-15[{Fe-1.5(II)-Fe-III (12)(mu(3)-OH)(12)(mu(4)-PO4)(4)}(B-alpha-PW9O34)(4)]center dot ca.130H(2)O (3), [{Cu-6(mu(3)-OH)(3)- (en)(3) (H2O)(3)}(B-alpha-PW9O34)]center dot 7H(2)O (4), [{Ni-6(mu(3)-OH)(3)(en)(3)(H2O)(6)}(B-alpha-PW9O34)]center dot 7H(2)O (5), [{Ni-6(mu(3)-OH)(3)(en)(2)- (H2O)(8)}(B-alpha-PW9O34)]center dot 7H(2)O (6), [{Ni6-(mu(3)-OH)(3)(dap)(2)(H2O)(8)} (B-alpha-PW9O34)]center dot 7H(2)O (7), and [(Ni-6(mu(3)-OH)(3)(en)(3)- (H2O)(6)}(B-alpha-SiW9O34)][Ni-0.5(en)]center dot 3.5 H2O (8) (en=ethylenediamine,dap=1,2-diaminopropane). These compounds have been structurally characterized by elemental analyses, IR spectra, diffuse reflectance spectra, thermogravimatric analysis, and X-ray crystallography. The double-cluster complex of phosphotungstate 1 simultaneously contains hepta- and hexa-Ni-II-substituted trivacant Keggin units [{Ni-7(mu(3)-OH)(3)O-2(dap)(3)(H2O)(6)}(B-alpha-PW9O34)](2-) and [Ni-6(mu(3)-OH)(3)(dap)(3)- (H2O)(6)}(B-alpha-PW9O34)]. The dimeric silicotungstate 2 is built up from two trivacant Keggin [B-alpha-SiW9O34](10-) fragments linked by an octa-Cu-II cluster. The main skeleton of 3 is a tetrameric cluster constructed from four tri-Fe-III-substituted [Fe-3(III)(mu(3)-OH)(3)(B-alpha-PW9O34)](3-) Keggin units linked by a central (Fe4O4)-O-II cubane core and four mu(4)-PO4 bridges. Complex 4 is an unprecedented three-dimensional extended architecture with hexagonal channels built by hexa-Cu-II clusters and trivacant Keggin [B-alpha-PW9O34](9-) fragments. The common feature of 5 - 8 is that they contain a B-cc-isomeric trivacant Keggin fragment capped by a hexa-Ni-II cluster, very similar to the hexa-Ni-II-substituted trivacant Kggin unit in 1. Magnetic measurements illustrate that 1, 2, and 5 have ferromagnetic couplings within the magnetic metal centers, whereas 3 and 4 reveal the antiferromagnetic exchange interactions within the magnetic metal centers. Moreover, the magnetic behavior of 4 and 5 have been theoretically simulated by the MAGPACK magnetic program package.