In search of 1,3-disila/germa/stannabicyclo[1.1.1]pentanes with short bridgehead-bridgehead distances and low ring strain energies

Abstract

The strain energies and through-space distances between the two bridgehead E atoms of a selection of 1,3-dimethyl-1,3-ditetrelbicyclo[1.1.1]pentanes (tetrel E = Si, Ge or Sn) were examined by quantum chemical calculations at MP2 and B3LYP levels. The aim is to identify which bridges lead to short through-space E,E distances, and simultaneously, to as low strain as possible. A short E,E distance should improve through-space interaction, and a low strain should promote the thermal stability and possibly also facilitate their synthesis. The bridges examined included CH 2 , CMe 2 , CtBu 2 , C(CH 2 ) n (n = 2-4), O, NMe, S, PMe, SiMe 2 , GeMe 2 , and SnMe 2 . The calculations indicate that the phospha bridge is a good compromise providing reasonably low strain as well as E,E through-space distances which are only longer than normal E E single bonds by factors of 1.06-1.10.

Electronic Excitations of 1,4-Disilyl-Substituted 1,4-Disilabicycloalkanes: A MS-CASPT2 Study of the Influence of Cage Size

“…The two bridgehead Si atoms are thereby in relatively close proximity to each other. We have previously computed the geometries and strain energies of the 1,3-disilabicyclo[1.1.1]pentane and 1,4-disilabicyclo [2.2.2]octane, as well as related systems, and found that these species are similarly or less strained than the all-carbon analogues, 10,11 which previously have been generated. 12,13 The compounds investigated herein should thus be realistic synthetic targets.…”