Photoelectron spectrum and reactivity of silylalkyl sulphides. Stabilization of radical cations by the β-silyl effect

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The effect of a β-silyl group on sulphur lone pair ionization energies has been re-investigated by use of ab initio and semi-empirical MNDO quantum-chemical calculations. The effect of the interaction between ns and σSiC{black star} orbitals and that of electron reorganization have been shown to be unimportant in the case of silyl-methyl-sulphides. To interpret the observed features of the ionization energies and reactivity, the electron release by the β-silyl group and hyperconjugative interactions have been considered. Stabilization brought about by β-substitution for the ground state of the radical cation is ca. 10 kcal mol-1 for alkyl (10.11 kcal mol-1) and silyl (9.48 kcal mol-1) substituents at the MP2 6-31G{black star}{black star}//HF 6-31G{black star}{black star} level of theory. The effects of the substituents are smaller on the neutral ground state of the molecules (6.80 and 0.50 kcal mol-1 for methyl and silyl groups, respectively) at the same level of theory. The observed low ionization energy of the β-silyl-substituted sulphides must be attributed to differences in the stabilization of the neutral ground states of the silyl- and alkyl-substituted derivatives rather than to the stabilization of the radical cationic ground state in the case of compounds of the type R3SiCH2SH.

Original languageEnglish
Pages (from-to)29-34
Number of pages6
JournalJournal of Organometallic Chemistry
Issue number1-2
Publication statusPublished - Feb 23 1993

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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