σ* Radical anions from halogen derivatives of perfluorobenzene
- 1 January 1981
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 77 (4) , 783-790
- https://doi.org/10.1039/f19817700783
Abstract
Electron addition to C6F5I, C6F5Br, the corresponding di-iodo and dibromo derivatives, and C6F5Cl gave only σ* radicals, as deduced from the e.s.r. spectra. Addition was achieved by exposing dilute solutions at 77 K to 60Co γ-rays, and was confirmed by observing a reduction in yield when electron-scavenging solutes were added. The σ* orbital containing the unpaired electron is shown to be largely confined to a single C—Cl, C—Br or C—I bond. However, for the ortho-disubstituted derivatives, the halogen hyperfine parameters were clearly reduced, indicating slight delocalisation into the neighbouring C—halogen bond. No features of the type characteristic of π* anions or the delocalized C6F6 – system were observed. The results are compared with those for the corresponding aryl halide σ* anions, which exhibit less delocalisation of the excess electron onto halogen.Keywords
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