3d/4f Sandwich Complex Based on Metallacrowns.

A novel lanthanide double-decker complex with nickel metallacrowns (MCs) as coordinating ligands has been synthesized. In the 3d/4f metallacrown complex Tb[12-MC-4], the central lanthanide ion is sandwiched between two [12-MC-4] units, forming an almost ideal square-antiprismatic coordination sphere. The resulting zenithal angles at the central lanthanide ion are smaller than those for previously reported sandwich compounds.