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

Abstract The hydrothermal reactions of trivacant Keggin A‐α‐XW 9 O 34 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 (μ 3 ‐OH) 3 O 2 (dap) 3 (H 2 O) 6 }(B‐α‐PW 9 O 34 )][{Ni 6 (μ 3 ‐OH) 3 (dap) 3 (H 2 O) 6 }(B‐α‐PW 9 O 34 )][Ni(dap) 2 (H 2 O) 2 ] ⋅ 4.5 H 2 O ( 1 ), [Cu(dap)(H 2 O) 3 ] 2 [{Cu 8 (dap) 4 (H 2 O) 2 }(B‐α‐SiW 9 O 34 ) 2 ] ⋅ 6 H 2 O ( 2 ), (enH 2 ) 3 H 15 [{Fe II 1.5 Fe III 12 (μ 3 ‐OH) 12 (μ 4 ‐PO 4 ) 4 }(B‐α‐PW 9 O 34 ) 4 ] ⋅ ca.130 H 2 O ( 3 ), [{Cu 6 (μ 3 ‐OH) 3 (en) 3 (H 2 O) 3 }(B‐α‐PW 9 O 34 )] ⋅ 7 H 2 O ( 4 ), [{Ni 6 (μ 3 ‐OH) 3 (en) 3 (H 2 O) 6 }(B‐α‐PW 9 O 34 )] ⋅ 7 H 2 O ( 5 ), [{Ni 6 (μ 3 ‐OH) 3 (en) 2 (H 2 O) 8 }(B‐α‐PW 9 O 34 )] ⋅ 7 H 2 O ( 6 ), [{Ni 6 (μ 3 ‐OH) 3 (dap) 2 (H 2 O) 8 }(B‐α‐PW 9 O 34 )] ⋅ 7 H 2 O ( 7 ), and [{Ni 6 (μ 3 ‐OH) 3 (en) 3 (H 2 O) 6 }(B‐α‐SiW 9 O 34 )][Ni 0.5 (en)] ⋅ 3.5 H 2 O ( 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 (μ 3 ‐OH) 3 O 2 (dap) 3 (H 2 O) 6 }(B‐α‐PW 9 O 34 )] 2− and [{Ni 6 (μ 3 ‐OH) 3 (dap) 3 (H 2 O) 6 }(B‐α‐PW 9 O 34 )]. The dimeric silicotungstate 2 is built up from two trivacant Keggin [B‐α‐SiW 9 O 34 ] 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 III 3 (μ 3 ‐OH) 3 (B‐α‐PW 9 O 34 )] 3− Keggin units linked by a central Fe II 4 O 4 cubane core and four μ 4 ‐PO 4 bridges. Complex 4 is an unprecedented three‐dimensional extended architecture with hexagonal channels built by hexa‐Cu II clusters and trivacant Keggin [B‐α‐PW 9 O 34 ] 9− fragments. The common feature of 5 – 8 is that they contain a B‐α‐isomeric trivacant Keggin fragment capped by a hexa‐Ni II cluster, very similar to the hexa‐Ni II ‐substituted trivacant Keggin 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.