Why are some (CH)4X6 and (CH2)6X4 polyheteroadamantanes so stable?
The representative isodesmic reactions shown in the Abstract graphic for (CH)(4)X(6) hexaheteroadamantane derivatives reveal energetic nonadditivity to remarkably different extents: while the electropositive element stabilizations are exceptionally large and the pnictide and hexaoxaadamantane stabilizations are more modest, the sulfur and selenium analogues are destabilized. Similar behavior is exhibited by (CH(2))(6)X(4) tetraheteroadamantanes. Analysis shows that aromaticity is not involved; the sign and magnitude of the nonadditivity depends on the interplay of hyperconjugation, electrostatic, and steric (lone pair repulsion) effects.
Wang
Yan
Y
School of Science, Beijing Institute of Technology, Beijing 100081, China.
Wu
Judy I-Chia
JI
Li
Qianshu
Q
Schleyer
Paul von Ragué
Pv