SiGe₂ and Ge₃: Cyclic Digermenes that Undergo Unexpected Ring‐Expansion Reactions^†

Abstract

The heavy cyclopropene analogues 1H‐siladigermirene R₄SiGe₂ (1 a) and 1H‐trigermirene R₄Ge₃ (1 b) have been obtained, and the X‐ray crystal structure of 1 a shows that it forms an isosceles triangle with a highly trans‐bent endocyclic GeGe bond (bending angle 51.0(2)°). The interaction of 1 a and 1 b with CH₂Cl₂ unexpectedly affords the unusual four‐membered‐ring compounds 2 a and 2 b as a result of ring expansion (see scheme: E=Si, Ge; R=SiMetBu₂).