Zintl-Klemm-Busmann concept

At a first glance the above mentioned electron transfer would require the application of the Zintl concept (designated in a later version as the Zintl-Klemm-Busmann concept [10]) as a tool for understanding the structural properties of alkali and alkaline earth amalgams. In simple words the Zintl concept says that the... 

In a salt-like description of these compounds, AE, the alkali metal A transfers its valence electron to the tetrel , and - in agreement with the Zintl-Klemm-Busmann concept [9] - the tetrel elements form P4-analogous tetrahedral clusters [ 4] . These highly charged clusters [ 4] are retained in a liquid ammonia solution of RbPb, as shown by Korber et al. via the crystallization of the ammoniate Rb4Pb4(NH3)2 [10]. The isotypic compounds A4Sii4(N 143)2 were obtained for A = Rb and Cs from reactions of the element Sn, as well as from Cs with Sn(C6Hs)4 in liquid ammonia [10]. 

Which, of course, brings me to the exception—the marvelous and useful Zintl concept.3 The simple notion, introduced by Zintl and popularized by Klemm, Busmann, Herbert Schafer, and others, is that in some compounds AxBy, where A is very electropositive relative to a main group element B, one could just think, that s all, think that the A atoms transfer their electrons to the B atoms, which then use them to form bonds. This very simple idea, in my opinion, is the single most important theoretical concept (and how not very theoretical it is ) in solid state chemistry of this century. And it is important not just because it explains so much chemistry, but because it forges a link between solid state chemistry and organic, or main group, chemistry. 

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