Structure and stability of propellane-like E[Formula: see text].

Propellane-like structures are an important building block for group-14 compounds. Therefore, in the present work, we study theoretically various such structures of the form E[Formula: see text] starting with the pure molecules for which E = E' = E″ = C, Si, Ge, or Sn. Subsequently, we study the systems with E ≠ E' = E″ and finally, we consider some selected cases molecules for which E, E', and E″ all are different. Special emphasis is put on identifying structural trends for the molecules with at least two different group-14 elements. The resulting scheme is, we believe, generally valid for group-14 based systems with more than one type of group-14 elements.