Synthesis of Silicon and Germanium-Containing Heterosumanenes via Rhodium-Catalyzed Cyclodehydrogenation of Silicon/Germanium-Hydrogen and Carbon-Hydrogen Bonds.

A three-step synthesis of C3-symmetric trisilasumanene and trigermasumanene, heteroanalogues of the π-bowl sumanene, was achieved using a threefold rhodium-catalyzed cyclodehydrogenation of Si/Ge-H and C-H bonds as the key step. Trigermasumanene was proven to adopt a planar geometry by single crystal X-ray diffraction for the first time. The optical properties were also investigated by UV-vis and fluorescence spectroscopy.