Efficient stereochemical communication in phosphine-amine palladium-complexes: Exploration of N-substituent effects in coordination chemistry and catalysis

Gergely Farkas, Zsófia Császár, Kristóf Stágel, Evelin Nemes, Szabolcs Balogh, Imre Tóth, Attila Bényei, György Lendvay, József Bakos

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Six-membered chelate complexes of type [Pd(1a-e)Cl2] (2a-e) and [Pd(1a-e)(η3-PhCHCHCHPh)]BF4 (3a-e) of a series of systematically varied chiral phosphine-amine ligands (S,S)-Ph2PCH(CH3)CH2CH(CH3)NHR 1a-e (R = benzyl 1a, R = ethyl 1b, R = (S)-α-phenylethyl 1c, R = isopropyl 1d, R = methyl 1e) have been studied. The complexes 2a-e were characterized by X-ray crystallography, DFT analysis and in solution by 1D and 2D NMR spectroscopy. A very good correlation has been observed between the steric demand of the N-substituent and the distortion of the chelate. Furthermore, it has been proved that sterically more demanding N-substituents are capable of distorting the chelate to a larger extent along one single, well defined conformational pathway. The careful variation of the N-substituent thus allows a precise stereochemical fine tuning of the metal's coordination sphere. As a substantiation of this concept, the investigation of complexes 3a-e revealed that the exo/endo ratio as well as the twisting of the allyl moiety around the Pd-allyl axis can easily be modified by the proper choice of the nitrogen substituent. Furthermore, Pd-catalysts with ligands 1a-e provided high enantioselectivities (up to 96%) in asymmetric allylic alkylation reactions.

Original languageEnglish
Pages (from-to)129-140
Number of pages12
JournalJournal of Organometallic Chemistry
Volume846
DOIs
Publication statusPublished - Jan 1 2017

Keywords

  • Allylic alkylation
  • Palladium
  • Phosphine-amine
  • Ring bending

ASJC Scopus subject areas

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

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