Stable isomers of sila- and germadodecahedrane. A semiempirical (AM1) investigation of the structure of 4/6 and 4/5/6 ring containing E20 (E = Si,Ge) systems

摘要

AM1 molecular orbital calculations with full geometry optimization of 4/6, 5/5 and 4/5/6 isomers of E_(20) (E = Si,Ge) show a clear preference of germanium to be accommodated in four membered rings and to achieve coordination numbers greater than 3 (V A). As a consequence, unlike C_(20) or Si_(20), the dodecahedral form of Ge_(20) was not localized on the potential surface, instead an opened structure derived from an octagermaprismane (IV B) can be predicted. Notable kinetic stabilization in the (SiR)_(20) systems is suggested by the HOMO-LUMO differences.