Polyhedral Silicon and Germanium Compounds

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Polyhedral carbon compounds such as tetrahedrane, prismane, and cubane have long fascinated chemists because of the unique properties and aesthetic appeal due to high symmetry. In an effort to enrich group 14 element chemisty, synthesis of the silicon and germanium analogues is a great challenge since it could lead to novel physical and chemical properties unexpected from the carbon compounds. However, such synthesis was thought to be impossible until recently. The successful syntheses, isolation, and characterization of polyhedral silicon and germanium compounds such as hexasilaprismane, hexagermaprismane, octasilacubane, and octagermacubane have been performed by this project. The research results are as follows.1) Synthesis and characterization of octasilacubane and octagermacubane.2) Structural determination of octasilacubane and octagermacubane by the X-ray crystallography.3) Synthesis and characterization of hexasilaprismane and hexagermaprismane.4) Stuctural determination of hexasilaprismane and hexagermaprismane by the X-ray crystallography.5) Physical properties by UV-Vis spectra and solid state NMR spectra.Prismanes are valence isomers of benzene, Dewar benzene, benzvalene. Indeed, the hexasilaprismane and hexagermaprismane afforded the corresponding Dewar benzene derivatives upon irradiation in solution at low temperature with light having wavelengths of 340-380 nm.