Can bridged 1,6-X-[10]annulenes (X = SiH(2), SiMe(2), PH, and S) exist?
[structure: see text] In contrast to the 1,6-X-[10]annulenes (X = CH(2), O, NH) with delocalized forms (c), their X = PH and S counterparts favor the bisnorcaradiene structures (b). Forms b and c are close in energy with X = SiH(2) and SiMe(2). The computed nucleus independent chemical shifts (NICS), show both annulenes (c) and cyclic polyenes (a) to be aromatic. Strain-introduced structural localization, e.g., due to four bulky SiMe(3) substituents, reduces but does not eliminate aromaticity.
Jiao
Haijun
H
Department of Chemistry, Shanxi Normal University, Linfen 041004, China.
van Eikema Hommes
Nicolaas J R
NJ
von Ragué Schleyer
Paul
P