1. σ-Aromaticity in an Unsaturated Ring: Osmapentalene Derivatives Containing a Metallacyclopropene Unit.
- Author
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Zhu, Congqing, Zhou, Xiaoxi, Xing, Hongjie, An, Ke, Zhu, Jun, and Xia, Haiping
- Subjects
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AROMATICITY , *METALLACYCLES , *ALLENE , *OSMIUM , *DENSITY functional theory - Abstract
In general, aromaticity can be clarified as π- and σ-aromaticity according to the type of electrons with major contributions. The traditional π-aromaticity generally describes the π-conjugation in fully unsaturated rings whereas σ-aromaticity may stabilize fully saturated rings with delocalization caused by σ-electron conjugation. Reported herein is an example of σ-aromaticity in an unsaturated three-membered ring (3 MR), which is supported by experimental observations and theoretical calculations. Specifically, when the 3 MR in cyclopropaosmapentalene is cleaved by ethane through two isodesmic reactions, both of them are highly endothermic (+29.7 and +35.0 kcal mol−1). These positive values are in sharp contrast to the expected exothermicity, thus indicating aromaticity in the 3 MR. Further nucleus-independent chemical shift and anisotropy of the current-induced density calculations reveal the nature of σ-aromaticity in the unsaturated 3 MR. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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