Reactions of Nine-Atom Germanium Clusters in Solutions

The discovery of dimers of nine-atom germanium clusters, [Ge9–Ge9]6–, showed that 2-center–2-electron exo-bonds can exist between such clusters. This formally 'oxidative' coupling of two clusters was the first redox reaction involving these species. This finding stimulated the systematic study of reactions of nine-atom germanium clusters with soft oxidizing agents, presented here. This study revealed that these clusters can bond to each other in different modes to form larger oligomers such as trimers, [Ge9=Ge9=Ge9]6–, and tetramers, [Ge9=Ge9=Ge9=Ge9]8–. Reactions of the clusters with Ph3Sb and Ph3Bi produced the first functionalized Zintl ions [Ph2Bi–Ge9–BiPh2]2–, [Ph2Sb–Ge9–SbPh2]2–, [Ph–Ge9–SbPh2]2–, and [Ph2Sb–Ge9–Ge9–SbPh2]4–. Initially the reaction mechanism for these additions was not clear but further detailed studies suggested that these reactions were in fact nucleophilic additions of the anions Ph2E– (E= Sb and Bi) to the naked clusters Ge9n-. The reaction mechanism is widely discussed in the thesis. These general ideas were explored further for possible use in more rational synthesis of similar derivatives of deltahedral Zintl ions by addition of other groups. Both mono- and di-substituted germanium clusters with –SnPh3, –SnMe3, –GePh3 and –CMe3 were obtained by similar reactions and were characterized by single crystal X-ray diffraction and in solution by NMR spectroscopy.