Untersuchungen zur Darstellung und Reaktivität metalloider Germaniumcluster (English shop)

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The aim of this work was to synthesise further metalloid cluster compounds of group 14. The focus was primarily on techniques that make it possible to prepare larger metalloid clusters. In this way, routes were to be opened up to metalloid cluster compounds that attain a size sufficient for them to be regarded as model compounds for the semiconductor industry, with its rapidly advancing miniaturisation of component structures and circuits.

For example, the disproportionation reaction of germanium(I) bromide made it possible to synthesise the two hitherto largest metalloid germanium clusters (THF)₆Li3Ge₁₄[Ge(SiMe₃)₃]₅ and (THF)₆Li₃Ge₁₄[Si(SiMe₃)₃]₅, whose cluster core exhibits a fullerene-like structure.

In addition, investigations into the reactivity of already existing metalloid cluster compounds were to be carried out. Among other things, the possibility of preparing, isolating and structurally characterising larger metalloid cluster compounds by build-up reactions was to be examined. Thus, with the metalloid cluster Ge₉[Si(SiMe₃)₃]₃-, subsequent reactions were carried out for the first time in the field of metalloid germanium clusters. With the transition metal fragments Cr(CO)₅ and Cr(CO)₃, the compounds [Ge₉[Si(SiMe₃)₃]₃Cr(CO)₅]- and [Ge₉ [Si(SiMe₃)₃]₃Cr(CO)₃]- were formed, in which the electronic influence of the transition metals on the germanium cluster core could be demonstrated.

The presence of the chromium atom in the clusters demonstrably altered the chemical properties. Thus, in gas-phase investigations of the degradation reaction of the clusters, a C–H activation could be observed which opened up completely new reaction channels and may possibly serve as a model system for transition-metal-catalysed C–H activations on germanium surfaces.

Furthermore, the linking of two Ge₉[Si(SiMe₃)₃]₃- molecules by the transition metals of group 10 (M = Cu, Ag, Au) to give [MGe₁₈[Si(SiMe₃)₃]₆]- anions was achieved. Quantum chemical calculations show that the two Ge₉ units also correspond electronically with one another via the transition metals, so that the possibility exists of obtaining, through further reaction with transition metals, an endless chain of [MGe₉] units that could be described as a one-dimensional conductor. Thus, here too, a cluster extension could be achieved through the use of transition metals.