Unsymmetrical carbene homologues: Isolable pyrido[b]-1,3,2λ2-diazasilole, -germole and -stannole and quantum-chemical comparison with unstable pyrido[c] isomers

Joachim Heinicke, Anca Oprea, Markus K. Kindermann, Tamás Karpati, Laszlo Nyulászi, Tamás Veszprémi

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Abstract

Reaction of the dilithium pyridine-2,3-diamide 1a-Li2 with SiCl4 and subsequent reduction of the resulting 2a with potasium or direct ring closure with GeCl2-dioxane or SnCl2 gave the stable carbene homologues 1,3-dineo-pentylpyrido[b]-1,3,2λ2-diazasilole (3a), -germole (4a) and -stannole (5a). Similarly, the dilithium pyridine-3,4-diamide 1b-Li2 and SiCl4 furnished the pyrido[c]-1,3,2λ-diazasilole (2b). However, attempts to obtain the silylene 3b as well as the analogous germylene and stannylene failed. Ab initio quantum chemical studies of model compounds IIIa, IIIb and benzo-1,3,2λ-diazasilole (IIIc) reveal a comparable thermodynamic stabilization. Unexpected similarlies of benzo and pyrido[b] derivatives and lower kinetic stability of carbene homologues of the pyrido[c]-type (b) correlate with high symmetry of the HOMO π charge densities in the former (IIIa has a nodal plane through the N-atom) and with unsymmetrical charge distribution in IIIb. All compounds are structurally characterized by NMR and MS, the carbene homologues also byu UV and 3a by photoelectron spectroscopy.

Original languageEnglish
Pages (from-to)541-545
Number of pages5
JournalChemistry - A European Journal
Volume4
Issue number3
DOIs
Publication statusPublished - Mar 1998

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Keywords

  • Ab initio calculations
  • Carbene homologous
  • Heterocycles
  • Photoelectron spectroscopy
  • Silanediyl

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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