Interplay between solvent and counteranion stabilization of highly unsaturated rhodium(III) complexes: Facile unsaturation-induced dearomatization

Mark Gandelman, Leonid Konstantinovski, Haim Rozenberg, David Milstein

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53 Citations (Scopus)


Abstraction of the chloride ligand from the PCN-based chloromethylrhodium complex 2 by AgX (X = BF4-, CF3SO3-) or a direct C-C cleavage reaction of the PCN ligand 1 with [(coe)2Rh(solv)n]+X- (coe = cyclooctene) lead to the formation of the coordinatively unsaturated rhodium(III) complexes 3. Compound 3a (X = BF4-) exhibits a unique medium effect; the metal center is stabilized by reversible coordination of the bulky counteranion or solvent as a function of temperature. Reaction of [(PCN)Rh(CH3)(CI)] with AgBArf in diethyl ether leads to an apparent rhodium(III) 14-electron complex 4, which is stabilized by reversible, weak coordination of a solvent molecule. This complex coordinates donors as weak as diethyl ether and dichloromethane. Upon substitution of the BF4- ion in [(PCN)Rh(CH3)]BF4 by the noncoordinating BArf- ion in a noncoordinating medium, the resulting highly unsaturated intermediate undergoes a 1,2-metal-to-carbon methyl shift, followed by β-hydrogen elimination, leading to the Rh-stabilized methylene arenium complex 5. This process represents a unique mild, dearomatization of the aromatic system induced by unsaturation.

Original languageEnglish
Pages (from-to)2595-2602
Number of pages8
JournalChemistry - A European Journal
Issue number11
Publication statusPublished - Jun 6 2003



  • Dearomatization
  • N,P ligands
  • Rhodium
  • Tridentate ligands
  • Unsaturated complexes

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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