Zintl ions endohedral

T. Fassler, S. D. Hoffmann, Endohedral Zintl ions intermetallic clusters. Angew. Chem. Int. Ed. 43 (2004) 6242. 

Figure 14.13 showed [Oeio] as a sole example of a 10-atom cluster. [Oeio] was reported in 1991, but the structure suffered from a crystallographic disorder (see Box 15.5). Homonuclear Zintl ions with more than nine cage atoms can be stabilized by the inclusion of an interstitial atom. Such endohedral Zintl ions (written as [M E ] where M is the interstitial atom) include ... 

The starting point for this case as described in (a) was the work of Cui et al. [17,18] when a new class of Zintl ions, plumbaspherene, Pbj, and stannaspherene, Sn, were characterized by photoelectron spectroscopy as hosts for building up a new type of endohedral clusters. Gas-phase experiments and theoretical investigations predicted a remarkable stability for the icosahedral plumbaspherene Pbj2 and the stannaspherene Sn cluster anions of Ih point symmetry. These empty polyanions have not yet been synthesized in crystalline form. 

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