Reactions of a Germacyclopropabenzene with Elemental Chalcogens: Syntheses and Structures of a Series of Stable 2<i>H</i>-Benzo[<i>c</i>][1,2]chalcogenagermetes

Thermal reactions of a stable germacyclopropabenzene, Tbt(Dip)GeC6H4 (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Dip = 2,6-diisopropylphenyl), with elemental chalcogens in C6D6 at 130 °C resulted in the formation of novel Ge-containing four-membered heterocycles, 2H-benzo[c][1,2]chalcogenagermete derivatives. This is the first example of a ring expansion reaction of cyclopropabenzene derivatives using elemental chalcogen, while several types of ring-opening reactions have been explored for cyclopropabenzene so far. In addition, the 2H-benzo[c][1,2]telluragermete is the first stable compound as a tellurete derivative. Structures of the chalcogenagermetes obtained here were elucidated by X-ray crystallographic analysis, and the experimentally obtained structural parameters were supported by theoretical calculations. The skeletons of chalcogenagermetes have very little strain in their four-membered rings annelated with a benzene ring.