Shuttling germanium atoms into branched polysilanes.

Lewis acid-catalyzed rearrangement reactions of trimethylgermylated small permethylated oligosilanes were found to show a strong tendency of the germanium atoms to move to the more highly silylated positions of the molecule. This makes possible the construction of molecules with high germanium content in the core parts of the molecules by the following repeated sequence: introduction of trimethylgermyl group followed by rearrangement. Quantum-mechanical computations at the B3LYP/6-311+G(d,p) level suggest that the exergonic rearrangement proceeds in a reaction cascade via germylium and silylium ions, which transform by 1,2-silyl and -methyl shifts.