Cluster complexes of Ge, Sn, and Pb

Extensive research over the past decade has greatly increased the number of cluster complexes of Ge, Sn, and Pb. The properties of M-M bonds and structures of these compounds are similar to the C-C bonds and carbon skeletons in organic compounds. Table 14.7.1 lists some of these cluster compounds that have been synthesized, isolated, and characterized by X-ray crystallography. In 

Structures of metallic cluster complexs of Ge and Sn (for clarity only the metal and halogen atoms are shown, and the organic groups have been omitted)  

The mixed-metal compound [Ge(SiMe3)3]2SnCl2 is a bent molecule [as shown in Fig. 14.7.3(b)], which forms two Ge-Sn bonds with bond lengths 263.6 and 262.6 pm. 

The tetramer [Ge(Cl)Si(SiMe3)3]4 forms a four-membered ring with Ge-Ge bond lengths 255.8 and 250.9 pm [as shown in Fig. 14.7.3(c)], while Ge4(Si Bu3 )4 is the first molecular germanium compound with a Ge4 tetrahedron, as shown in Fig. 14.7.3(d). 

The hexamer Ge6[CH(SiMe3)2]6 has a prismane structure as shown in Fig. 14.7.3(e). The Ge-Ge distances within the two triangular faces are 258 pm, being longer than those in the quadrilateral edges, which are 252 pm. On the other hand, the hexamer (SnPh2)6 exists in the chair conformation, (as shown in Fig. 14.7.3(f)) with Sn-Sn distances 277 to 278 pm. 

---