Structure and characterization of zero- to two-dimensional compounds built up of the sandwich-type clusters and transition-metal linkers

Five new heteropolyoxotungstates K2Na2Mn2(H2O)12[Mn2(H2O)10Mn4(H2O)2(XW9O34)2] 18H2O (X ¼ Ge, 1; X ¼ Si, 2), Na4[Mn4 (H2O)18Mn4(H2O)2(XW9O34)2] 22H2O (X ¼ Ge, 3; X ¼ Si, 4) and K3Na5[Mn2(H2O)6Mn4(H2O)2(SiW9O34)2] 23.5H2O (5) have been obtained by the routine synthetic reactions in aqueous solution. In 1 and 2, two isolated Mn2+ ions are covalently linked to the sandwich-type polyoxoanions [Mn4(H2O)2(B-a-XW9O34)2]12 (X ¼ Ge or Si) by two m2-oxygen atoms resulting in the disupporting sandwich-type polyoxometalates (POMs). Compounds 3 and 4 are built from the disupporting sandwich-type polyoxoanions 1 and 2, linked by additional four Mn2+ ions to construct a 1D ladder-like chain-like structure, which is rarely observed in the POM chemistry. Compound 5 represents the first example of the 2D structure consisting of the sandwich-type polyoxoanion [Mn4(H2O)2(SiW9O34)2]12 and the binuclear {Mn2(H2O)6}4+ group. The magnetic studies of compounds 1, 4 and 5 indicate that the antiferromagnetic interactions are predominant in the three compounds between Mn(II) metal ions