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Doped Semimetal Clusters: Ternary, Intermetalloid Anions [Ln@Sn7Bi7]4– and [Ln@Sn4Bi9]4– (Ln = La, Ce) with Adjustable Magnetic Properties

Lips, Felicitas, Hołyńska, Małgorzata, Clérac, Rodolphe, Linne, Uwe, Schellenberg, Inga, Pöttgen, Rainer, Weigend, Florian, Dehnen, Stefanie
Journal of the American Chemical Society 2012 v.134 no.2 pp. 1181-1191
anions, cations, magnetic properties, metalloids, oxidation, salts, topology
Two K([2.2.2]crypt) salts of lanthanide-doped semimetal clusters were prepared, both of which contain at the same time two types of ternary intermetalloid anions, [Ln@Sn₇Bi₇]⁴– and [Ln@Sn₄Bi₉]⁴–, in 0.70:0.30 (Ln = La) or 0.39:0.61 (Ln = Ce) ratios. The cluster shells represent nondeltahedral, fullerane-type arrangements of 14 or 13 main group metal atoms that embed the Ln³⁺ cations. The assignment of formal +III oxidation states for the Ln sites was confirmed by means of magnetic measurements that reveal a diamagnetic La(III) compound and a paramagnetic Ce(III) analogue. Whereas the cluster anions with a 14-atomic main-group metal cage represent the second examples in addition to a related Eu(II) cluster published just recently, the 13-atomic cages exhibit a yet unprecedented enneahedral topology. In contrast to the larger cages, which accord to the Zintl–Klemm–Busmann electron number–structure correlation, the smaller clusters require a more profound interpretation of the bonding situation. Quantum chemical investigations served to shed light on these unusual complexes and showed significant narrowing of the HOMO–LUMO gap upon incorporation of Ce³⁺ within the semimetal cages.