Deciphering the mechanism of the nickel-catalyzed hydroalkoxylation reaction: A combined experimental and computational study

Alexis Mifleur, Delphine S. Mérel, André Mortreux, Isabelle Suisse, Frédéric Capet, Xavier Trivelli, Mathieu Sauthier, Stuart Alan Macgregor

Research output: Contribution to journalArticle

13 Citations (Scopus)
34 Downloads (Pure)

Abstract

The [Ni(0)(cod)b2]/PP-catalyzed hydroalkoxylation of butadiene to form butenyl ethers is studied mechanistically, where PP = 1,4-bis(diphenylphosphino)butane (dppb) and 1,2-bis(diphenylphosphinomethyl)-benzene (dppmb). Experimental studies suggest the intermediacy of [(PP)-Ni(0)(butadiene)] and [(PP)Ni(II)(allyl)] intermediates and rule out the involvement of Ni-H species. The related species [(dppb)Ni(0)(1,4-diphenylbutadiene)], 1, and [(PP)Ni(II)(crotyl)(Cl)] complexes 2 (PP = dppmb) and 3 (PP = dppb) have been synthesized and characterized on the basis of VT NMR spectroscopy and X-ray crystallographic studies. Compounds 2 and 3 are shown to be catalytically competent for the hydroalkoxylation reaction. Computational studies on [(dppmb)Ni(0)(butadiene)] indicate a facile protonation that forms a cationic allylic intermediate [(dppmb)Ni(II)(η-C4H7)]OMe. C-O bond formation then occurs via external attack by the solvent-stabilized methoxide nucleophile. Hydroalkoxylation proceeds with modest computed barriers of ca. 18 kcal/mol, and the butenyl ether product formation is only marginally exergonic. Overall, the results are consistent with initial kinetic control leading to the major branched isomer followed by a reversible isomerization process operating under thermodynamic control.

Original languageEnglish
Pages (from-to)6915-6923
Number of pages9
JournalACS Catalysis
Volume7
Issue number10
Early online date30 Aug 2017
DOIs
Publication statusPublished - 6 Oct 2017

Keywords

  • Allyl
  • Butadiene
  • Hydroalkoxylation
  • Mechanism
  • Nickel

ASJC Scopus subject areas

  • Catalysis

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