Competing reactions of hypercoordinate silicon dichelates

Inna Kalikhman, Boris Gostevskii, Evgenia Kertsnus, Stephan Deuerlein, Dietmar Stalke, Mark Botoshansky, Daniel Kost

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17 Scopus citations


Neutral hexacoordinate silicon complexes derived from hydrazide chelating ligands with imino-donor groups, and their pentacoordinate ionic dissociation products, undergo facile intramolecular aldol-type condensation catalyzed by their chloride counterion leading to formation of a third chelate ring. In analogous silacyclobutane dichelates, in the absence of halide counterion, a similar uncatalyzed rearrangement takes place, accompanied by opening of the four-membered ring. In the absence of a-protons necessary for the condensation, the four-membered ring residue adds directly to one of the imino-carbon atoms forming a new C-C bond and closing a different chelate ring. This latter addition to the imino carbon is the preferred reaction pathway, even in the presence of 12 α-protons, when cyanide ion replaces the chloride counterion and acts as nucleophile. The cyanide reactivity is rationalized in terms of the HSAB concept. An unusual intramolecular rearrangement involving the migration of a t- butyl group from silicon to carbon, while enabling the unprecedented attachment of a third hydrazide chelating agent, leading to a hexacoordinate trichelate complex, is presented.

Original languageEnglish
Pages (from-to)1029-1034
Number of pages6
JournalJournal of Physical Organic Chemistry
Issue number12 SPEC. ISS.
StatePublished - 1 Dec 2008


  • Aldol condensation of imines
  • Hypercoordinate silicon
  • Molecular rearrangement
  • Silacyclobutane complex
  • Silicon trichelate


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