Studies on electronic effects in O-, N- and S-chelated ruthenium olefin-metathesis catalysts

Eyal Tzur, Anna Szadkowska, Amos Ben-Asuly, Anna Makal, Israel Goldberg, Krzysztof Woźniak, Karol Grela, N. Gabriel Lemcoff

Research output: Contribution to journalArticlepeer-review

Abstract

A short overview on the structural design of the Hoveyda-Grubbs-type ruthenium initiators chelated through oxygen, nitrogen or sulfur atoms is presented. Our aim was to compare and contrast O-, N- and S-chelated ruthenium complexes to better understand the impact of electron-withdrawing and -donating substituents on the geometry and activity of the ruthenium complexes and to gain further insight into the trans-cis isomerisation process of the S-chelated complexes. To evaluate the different effects of chelating heteroatoms and to probe electronic effects on sulfur- and nitrogen-chelated latent catalysts, we synthesised a series of novel complexes. These catalysts were compared against two well-known oxygen-chelated initiators and a sulfoxide-chelated complex. The structures of the new complexes have been determined by single-crystal X-ray diffraction and analysed to search for correlations between the structural features and activity. The replacement of the oxygen-chelating atom by a sulfur or nitrogen atom resulted in catalysts that were inert at room temperature for typical ring-closing metathesis (RCM) and cross-metathesis reactions and showed catalytic activity only at higher temperatures. Furthermore, one nitrogen-chelated initiator demonstrated thermo-switchable behaviour in RCM reactions, similar to its sulfur-chelated counterparts.

Original languageEnglish
Pages (from-to)8726-8737
Number of pages12
JournalChemistry - A European Journal
Volume16
Issue number29
DOIs
StatePublished - 2 Aug 2010

Keywords

  • Carbenes
  • Chelates
  • Ligand design
  • Metathesis ruthenium

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