Structures and stabilities of three-membered rings containing a hypervalent atom

Citation
H. Ikeda et S. Inagaki, Structures and stabilities of three-membered rings containing a hypervalent atom, J PHYS CH A, 105(47), 2001, pp. 10711-10718
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF PHYSICAL CHEMISTRY A
ISSN journal
1089-5639 → ACNP
Volume
105
Issue
47
Year of publication
2001
Pages
10711 - 10718
Database
ISI
SICI code
1089-5639(20011129)105:47<10711:SASOTR>2.0.ZU;2-3
Abstract
We investigated the structures and the stabilities of the three-membered ri ngs FnX-CH2-Y (X = Si, P, S; Y = CH2, NH, O; n = 2 or 3) containing a hyper valent atom (X) and disclosed their origins by developing and applying an e lectron-pair bond model for hypervalent molecules. For the rings containing a pentacoordinated Si or P atom, the (ap, eq) isomers with the ring bonds in the apical and equatorial positions are local minima, while the (eq, eq) isomers with both ring bonds in the equatorial positions are the transitio n states of pseudorotation reactions due to the high ring strains. In contr ast, the (ap, eq) and (eq, eq) isomers for the rings containing a tetracoor dinated P or S atom are both local minima. The tetracoordinated species are less strained than the pentacoordinated ones because of the effect of the lone pair on X giving rise to less antibonding properties of the electron d elocalization between the geminal ring bonds on X. Moreover, the more strai ned (eq, eq) isomers are surprisingly more stable than the (ap, eq) isomers in most of the tetracoordinated species. The relative stabilities are cont rolled by the repulsion between the lone pair on X and the apical bond. The relative stabilities of the (ap, eq) isomers with Y (= NH, O) in the apica l and equatorial positions are predicted and discussed.