REDUCED CLUSTERS WITH REMARKABLE TOPOLOGICAL AND ELECTRONIC-PROPERTIES OF THE TYPE OF [V18O42(X)]N-(X=SO4,VO4) WITH TD-SYMMETRY AND RELATED CLUSTERS [V(18-P)AS2PO42(X)]M-(X=SO3,SO4,H2O-P=3,4)

The novel cluster-compounds Na6[V18O42H9(VO4)].21 H2O, (NH4)8[V18O42(SO4)].25 H2O, K6[V15As6O42(H2O)].8 H2O, (NH4)6[V14As8O42(SO3)], (NH4)6[V14As8O42(SO4)] and [N(CH3)4]4[V14As8O42(H2O)] were prepared and characterized by IR- and UV/Vis/NIR-spectroscopy, magnetic measurements and complete crystal structure analysis. For structural data see Inhaltsubersicht. Topological relations to the rhombicuboctahedron spanned by 24 O-atoms of the genuine hypothetical alpha-Keggin ion, at which the square planes are capped by V = O or As2O groups, are discussed. Of particular interest are the "extended" Keggin ions [V18O42(X)]n- (X = SO4, VO4), (formaly derived from the hypothetical genuine alpha-Keggin ion by addition of six V = O groups) which have quite different electron populations in spite of the same structure of their cluster shells.