The photolysis of cyclopentadienyl compounds of tin and mercury. Electron spin resonance spectra and electronic configuration of the cyclopentadienyl, deuteriocyclopentadienyl, and alkylcyclopentadienyl radicals
- 1 January 1980
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 6,p. 941-948
- https://doi.org/10.1039/p29800000941
Abstract
Cyclopentadienyl derivatives of tin(IV) and mercury(II) and alkylcyclopentadienyl derivatives of mercury(II) are photolysed in solution to show the e.s.r. spectra of the appropriate radicals RC5H4·(R = H, D, Me, Et, Pri, or But). The C5H5· radical is a planar π-radical with average D5h symmetry, and its spectrum is broadened in the presence of organic bromides, perhaps by a charge-transfer mechanism. The introduction of alkyl groups breaks the degeneracy of the ψA and ψS molecular orbitals of the π-system by electron release, destabilising the ψS MO, and the e.s.r. spectrum reflects the spin density distribution in the configuration ψA 2ψS 1. Deuterium has a small but detectable perturbing effect: the ψA MO is destabilised by ca. 100 J mol–1, and thermal mixing of the two energy levels results in the configuration ψS 1.515ψA 1.485. This is compatible with the model of a vibrational perturbation of the resonance integral β, rather than of the Coulomb integral α.Keywords
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