Silicon and Germanium-Based Sesquioxanes as Versatile Building Blocks for Cage Metallacomplexes. A Review

In the present paper, a rapidly developing field of polynuclear cage metallasilsesquioxanes and metallagermsesquioxanes chemistry is surveyed. Deliberate synthesis techniques aimed at the cages of specific nuclearity are described with the emphasis placed onto analysis of similarities and differences between silicon- and germanium-based substances. General approaches towards design of polymeric supramolecular assemblies based on cage metallasilsesquioxanes and metallagermsesquioxanes are outlined and illustrated with appropriate examples. Striking catalytic properties of the title compounds in homogeneous oxidation reactions are noted as one of their prospective application field.