Donor-stabilized silyl cations. Part 7: Neutral hexacoordinate and ionic pentacoordinate silicon chelates with N-isopropylideneimino-acylimidato ligands

Inna Kalikhman, Boris Gostevskii, Olga Girshberg, Akella Sivaramakrishna, Nikolaus Kocher, Dietmar Stalke, Daniel Kost

Research output: Contribution to journalArticlepeer-review

37 Scopus citations

Abstract

Silicon complexes with a new chelating donor group, the isopropylideneimino-acylimidato(N,O) moiety [OC(R)=NN=CMe2], have been prepared (9-12, 15), and their properties are compared with previously described silicon chelates (1, 2, and 16, respectively). The new ligand acts as a more powerful donor than the NNMe2 ligand, based on three criteria: (a) the new complexes form directly as pentacoordinate siliconium salts 9-12, i.e., the expected neutral hexacoordinate precursors ionize spontaneously; (b) comparison of crystallographic bond lengths with those of the NNMe2 complexes shows consistently shorter N-Si coordination bonds and longer Si-halogen bonds in equally substituted new relative to the previously studied complexes; (c) while in the previous series 1, the dihalo complexes 20-22, 25, resisted ionization at any temperature or solvent, the dibromo-isopropylideneimino complexes 19a and 19b ionize reversibly upon decrease of temperature in chloroform solution. Steric congestion forces the trans-dihalo configuration on the dichloro and bibromo complexes 18, 19. The ionization-resistant complexes 17, 18 and the partly ionized 19 form stable ionic siliconium salts when their counterions are replaced by I-, BPh4-, or by reaction with strong Lewis acids, AlCl3 and AlBr3.

Original languageEnglish
Pages (from-to)202-214
Number of pages13
JournalJournal of Organometallic Chemistry
Volume686
Issue number1-2
DOIs
StatePublished - 1 Dec 2003

Keywords

  • Hexacoordinate
  • Ionization
  • Pentacoordinate
  • Silicon
  • Silyl cation

ASJC Scopus subject areas

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

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