Ionic-Radius-Driven Selection of the Main-Group-Metal Cage for Intermetalloid Clusters [Ln@PbxBi14-x]q- and [Ln@PbyBi13-y]q- (x/q=7/4, 6/3; y/q=4/4, 3/3)

Reactions of the binary, pseudo-homoatomic Zintl anion (Pb2Bi2)(2-) with Ln(C5Me4H)(3) (Ln=La, Ce, Nd, Gd, Sm, Tb) in the presence of [2.2.2] crypt in ethane-1,2-diamine/ toluene yielded ten [K([2.2.2] crypt)]+ salts of lanthanide-doped semimetal clusters with 13 or 14 surface atoms. Single-crystal X-ray diffraction and energy-dispersive X-ray spectroscopy indicated the presence of the anions [Ln@ Pb6Bi8](3-), [Ln@Pb3Bi10](3-), [Ln@Pb7Bi7](4-), or [Ln@Pb4Bi9]4(-) in single or double salts; the latter showed various ratios of the components in the solid state. The anions are the first ternary intermetalloid clusters comprising only elements of the sixth period of the periodic table, namely, Pb, Bi and lanthanides. This study, which was complemented by ESI mass spectrometry and 139La NMR spectroscopy in solution, rationalizes a continuous development of the ratio of 13: 14-atom cages with the ionic radius of the embedded Ln(3+) ion, which seems to select the most suitable cage type. Quantum chemical investigations helped to analyze this situation in more detail and to explain the observed subtle influence of the atomic radii. Magnetic measurements confirmed that the embedded Ln(3+) ions keep their expected paramagnetic or diamagnetic nature.