Toward stable N-heterocyclic silylenes at theoretical levels

M. Z. Kassaee, H. Zandi, M. R. Momeni, F. A. Shakib, M. Ghambarian

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


To appreciate the chemistry of N-heterocyclic silylenes, eight silylenic isomers derived from 2-, 3-, and 4-silapyridines (1, 2, and 3, respectively) are compared and contrasted at B3LYP/AUG-cc-pVTZ//B3LYP/6-31+G* and MP2/6-311++G**//B3LYP/6-31+G* levels of theory. Specifically three of eight silylenic isomers are derived from 1: 1H-, 3H-, and 5H-2-silapyridine-2-ylidene (1a, 1b, and 1c, respectively), three from 2: 2H-, 4H-, and 6H-3-silapyridine-3-ylidene (2a, 2b, and 2c, respectively), and finally, two silylenic isomers from 3: 1H-, and 5H-4-silapyridine-4-ylidene (3a, and 3b, respectively). Various thermodynamic parameters are calculated for these eight silylenic minima, along with a kinetic focus on their intramolecular rearrangements to the corresponding silapyridines (1-3). From a thermodynamic point of view, 1a and 3a are the most stable with singlet-triplet energy gaps near to that of Denk's synthesized silylene, i.e. 59.0 and 46.6 vs. 53.0 kcal/mol, respectively. The calculated energy barrier for the [1,2]-H shift of 1a to 1 is 63.4 kcal/mol compared to 80.3 kcal/mol for the [1,4]-H shift of 3a to 3. This study signifies the thermodynamic and kinetic stabilities of 3a which appears compatible with the reported 1a. Considering the σ-donor characteristic of the stable silylenes, the highest nucleophilicity and the lowest electrophilicity is calculated for 3a.

Original languageEnglish (US)
Pages (from-to)16-21
Number of pages6
JournalJournal of Molecular Structure: THEOCHEM
Issue number1-3
StatePublished - Nov 15 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry


  • Ab initio
  • DFT
  • Electrophilicity
  • N-Heterocyclic silylene
  • Nucleophilicity
  • Silapyridine


Dive into the research topics of 'Toward stable N-heterocyclic silylenes at theoretical levels'. Together they form a unique fingerprint.

Cite this