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)[Mn-2(H2O)(10)Mn-4(H2O)(2)(XW9O34)(2)] center dot 18H(2)O (X = Ge, 1; X = Si, 2), Na-4[Mn-4 (H2O)(18)Mn-4(H2O)(2)(XW9O34)(2)]center dot 22H(2)O (X = Ge, 3; X = Si, 4) and K3Na5[Mn-2(H2O)(6)Mn-4(H2O)(2)(SiW9O34)(2)]center dot 23.5H(2)O (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 [Mn-4(H2O)(2)(B-alpha-XW9O34)(2)](12-) (X = Ge or Si) by two mu(2)-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 ID 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 [Mn-4(H2O)(2)(SiW9O34)(12-) and the binuclear {Mn-2(H2O)(6)}(4+) group. The magnetic studies of compounds 1, 4 and 5 indicate that the anti ferromagnetic interactions are predominant in the three compounds between Mn(II) metal ions. (C) 2008 Elsevier Inc. All rights reserved.