Rhodium complexes with chiral counterions: Achiral catalysts in chiral matrices

Romano Dorta, Linda Shimon, David Milstein

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43 Citations (Scopus)

Abstract

The neutral complexes [Rh(I)(NBD)((1S)-10-camphorsulfonate)] (2) and [Rh(I)((R)-N-acetylphenylalanate)] (4) reacted with bis-(diphenylphosphino)ethane (dppe) to form the cationic Rh(I)(NBD)(dppe) complexes, 5 and 6, respectively, accompanied by their corresponding chiral counteranions. Analogously, 4 reacted with 4,4′-dimethylbipyridine to yield complex 7. Complexes 5 and 6 disproportionated in aprotic solvents to form the corresponding bis-diphosphine complexes 8 and 9, respectively. 8 was characterized by an X-ray crystal structure analysis. In order to form achiral Rh(I) complexes bearing chiral countercations new sulfonated monophosphines 13-16 with chiral ammonium cations were synthesized. Tris-triphenylphosphinosulfonic acid (H3TPPS, 11) was used to protonate chiral amines to yield chiral ammonium phosphines 14-16. Thallium-tris-triphenylphosphinosulfonate (Tl3TPPS, 12) underwent metathesis with a chiral quartenary ammonium iodide to yield the proton free chiral ammonium phosphine 13. Phosphines 15 and 16 reacted with [Rh(NBD)2]BF4 to afford the highly charged chiral zwitterionic complexes [Rh(NBD) (TPPS)2][(R)-N, N-dimethyl-1-(naphtyl)ethylammonium] 5 (17) and [Rh(NBD)(TPPS)2][BF4] [(R)-N, N-dimethyl-phenethylammonium]6 (18), respectively. Complexes 5, 6, and 18 were tested as precatalysts for the hydrogenation of de-hydro-N-acetylphenylalanine (19) and methyl-(Z)-(α) -acetoamidocinnamate (MAC, 20) under homogeneous and heterogeneous (silica-supported and self-supported) conditions. None of the reactions was enantioselective.

Original languageEnglish
Pages (from-to)751-758
Number of pages8
JournalJournal of Organometallic Chemistry
Volume689
Issue number4
DOIs
Publication statusPublished - Feb 16 2004

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Keywords

  • Catalysis
  • Chiral counterions
  • Hydrogenation
  • Rhodium

ASJC Scopus subject areas

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

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