Cation control on the crystal organization of hexanuclear carbonyl cluster anions

The crystal structures of 28 hexanuclear carbonyl cluster anions have been investigated by means of empirical packing potential energy calculations, van der Waals volume analysis, and computer graphics. Data were retrieved from the Cambridge Structural Database. The relationship between shape, size, and charge of the component ions and the formation of preferential aggregates (piles, ''snakes'', layers) in the crystal lattice has been analyzed. It has been shown that, with large organic cations, the packing pattern is essentially that of molecular mixed crystals, while small cations drive toward monodimensional aggregation of the anions. It has been shown that there is a (fairly precise) ratio between the relative volumes of the component ions above which one-dimensional or two-dimensional networks are preferentially established. Some representative cases are discussed in detail.