Zintl ion clusters

It has been shown that a variety of substituents can be attached to the outside of the group 14 Zintl ion clusters in exo positions (i.e., not vertex or interstitial positions) [70,73-78]. A variety of alkyl, aryl, and main group moieties have been attached to Ge9 and Sn9 clusters. The structures of these clusters are similar to some organos-tannane clusters prepared via different synthetic routes. This burgeoning class of compounds is rapidly developing however, little is known about the effect of the exo-substituents on the dynamic properties of the clusters. Only the RSng ions, where R = i-Pr, t-Bu, and SnCys, Sn- -Bu3, have been studied in detail [70]. 

Kesanli B, Fettinger J, Eichhom B (2001) The closo-[Sn9M(CO)3] - Zintl ion clusters where M = Cr, Mo, W two stmctural isomers and their dynamic behavior. Chem A Euro J 7 5277-5285... 

Furthermore, evident stmctural similarities between compounds obtained through reaction with Zintl ion clusters and ligand-stabilized cage molecules occur (Table 11). 

Figure 13 Naked Zintl ion clusters Sb4 arachno),Sn (closo), and Snp " (nido)...

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

In an effort to make the distannyne, Ar Sn=SnAr (Ar = 2,6-(2,4,6-Pr 3C6H2)2C6H3), Ar SnH was heated in toluene hydrogen was eliminated but SnC bonds also were cleaved, and gave the paramagnetic cluster Ar 3Sn9 59 (g= ca. 2.031), with a structure that is based on the 21-electron [Sng]3- cage that is known as a Zintl ion.478... 

Zintl ions are polyanions formed by anion clustering in ionic alloys. Two categories were considered those that fit the so-called Zintl-Klemm concept and those that are electron-deficient. 

Structure and Bonding in Zintl Ions and Related Main Group Element Clusters... 

Abstract This chapter reviews the methods that are useful for understanding the structure and bonding in Zintl ions and related bare post-transition element clusters in approximate historical order. After briefly discussing the Zintl-Klemm model the Wade-Mingos rules and related ideas are discussed. The chapter concludes with a discussion of the jellium model and special methods pertaining to bare metal clusters with interstitial atoms. 

Keywords Jellium model Metal clusters Wade-Mingos rules Zintl ions Contents... 

The efforts to rationalize the formulas and structures of Zintl ions and related species predated extensive definitive structural information on anionic post-transition metal clusters obtained by Corbett and his group in the 1970s [8, 9]. After enough such structural information on the bare post-transition metal clusters became available, the resemblance of their polyhedra to the known polyhedral boranes became apparent. For this reason, the simple Zintl-Klemm concept has been largely superseded by newer, more advanced descriptions of chemical bonding in such clusters, initially those applied to the polyhedral boranes. 

The Relationship of Zintl Ions to Polyhedral Boranes The Wade-Mingos Rules and the Aromaticity of Clusters... 

The next development in the understanding of structure and bonding in the Zintl ions recognized their relationship to the polyhedral boranes and the isoelectronic carboranes. Then the Wade-Mingos rules [13-16], which were developed to understand the structure and bonding in polyhedral boranes, could be extended to isovalent Zintl ions and related post-transition element clusters. 

Fig. 3 Examples of the shapes of some Zintl ions and related clusters...

This review will focus on the NMR properties of Zintl ion complexes, namely the solution properties of the ions where E = Si, Ge, Sn, Pb, and the products derived from those clusters. Closely related clusters prepared by other means, such as the recent, elegant organo polystannane work of Schnepf, Power, Huttner, and Fischer, are briefly mentioned but are not the focus of this review. Related overviews of dynamic organometallic complexes [1,2] and the stmcture and bonding of Zintl ions [3-5] can be found in previous reviews and in other chapters of this book. 

The first transition metal derivatives of a Zintl ion was prepared by Teixidor et al. in 1983 in reactions between Pt(PPli4)4 and en solutions of the Eg (E = Sn, Pb) [25, 26]. Despite being the first examples in this important class of clusters, the complexes have yet to be isolated and their structures and compositions remain unknown. The authors propose that complexes have a (PPh3)2PtSng stoichiometry and a nido-ty structure. Based on comparisons with NMR parameters from the past 30 years and the stoichiometry of the reactions described by Teixidor et al., we believe that the Rudolph compounds are most likely 22-electron cZos )-Pf E9Pt (PPh3) complexes. Our rationale is given below. 

The dynamic properties of these two complexes are perhaps the most surprising and interesting of the transition metal Zintl ion complexes. The clusters have markedly different structures but are both prolate in nature with several different Sn environments. The tin atoms at opposite ends of both structures are separated by nearly 9 A, but all 17 atoms are in fast intramolecular exchange on the NMR time scale. 

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