Ionization potentials of silenes (R′2Si=CR2). Experiment and theory

Michael Bendikov, Bahman Solouki, Norbert Auner, Yitzhak Apeloig

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Abstract

We have measured the photoelectron (PE) spectra of two new silenes: the kinetically stable long-lived silene t-BuMe2Si(Me2Si)Si=Ad (3) and a transient silene which was generated in the gas phase by pyrolysis of the corresponding precursor. Previously, PE spectra of only two transient silenes have been reported. The ionization potential (IP) of 3 is 6.9 eV, 2 eV lower than that of H2Si=CH2. Quantum-mechanical calculations reproduce quite well the experimental IPs. The trends in IP1 are well-reproduced by calculations of the silene's HOMO, even at the HF/6-31G(d)//HF/6-31G(d) level of theory. However, the correct absolute IPs are reproduced quantitatively (to within 0.1-0.2 eV) only at a higher theoretical level, such as ROVGF/6-311+G(2df,p), MP4/6-311+G(2df,p), or B3LYP/6-311+G(2df,p). Lower level ab initio calculations, such as ROVGF/3-21G(d) and ROVGF/6-31G(d), reproduce the trends in the IPs. The theoretical and experimental data show that the effect of substituents on the HOMO energy of silenes is slightly smaller than in the corresponding alkenes. Disilyl substitution at the doubly bonded Si atom and dimethyl substitution at the doubly bonded C atom raise the HOMO energy, by 0.6 and 0.8 eV, respectively.

Original languageEnglish
Pages (from-to)1349-1354
Number of pages6
JournalOrganometallics
Volume21
Issue number7
DOIs
Publication statusPublished - Apr 1 2002

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ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

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