New Ionic Crystals of Oppositely Charged Cluster Ions and Their Characterization

By reacting Keggin-type polyoxometalate cluster anions H2W12O406- (metatungstate) or CoIIW12O406- (tungstocobaltate)
with the large aluminum cluster polycation [Al30O8(OH)56(H2O)26]18+, Keggin ion based molecular ionic compounds
[δ-Al13O4(OH)24(H2O)12][XW12O40](OH)·nH2O (X = H2 (1) and Co (2); n ≅ 20) and [W2Al28O18(OH)48(H2O)24][H2W12O40]2·55H2O (3) were obtained. The polygon-shaped cluster ions are packed alternately through intercluster
hydrogen bonds as well as electrostatic interactions, leaving large pores, which result from the packing of large
clusters. The clusters are arranged in square pyramidal geometries, showing face-to-face interactions between
them. The isolation of metastable [δ-Al13O4(OH)24(H2O)12]7+ and the formation of a new transition metal substituted
aluminum heteropolycation [W2Al28O18(OH)48(H2O)24]12+ in 1−3 result from the slow fragmentation and recombination
of Al30 in the presence of suitable counter cluster anions with similar shape and charge.