Z-selective, catalytic internal alkyne semihydrogenation under H 2/CO mixtures by a niobium(III) imido complex

Thomas L. Gianetti, Neil C. Tomson, John Arnold, Robert G. Bergman

Research output: Contribution to journalArticlepeer-review

73 Scopus citations

Abstract

The discovery of a Nb(III)-mediated catalytic hydrogenation of internal alkynes to (Z)-alkenes that proceeds through an unprecedented mechanism is reported. The mechanistic proposal involves initial reduction of the alkyne by the Nb(III) complex (BDI)Nb(N tBu)(CO) 2 to provide a Nb(V) metallacyclopropene, itself capable of σ-bond metathesis reactivity with H 2. The resulting alkenyl hydride species then undergoes reductive elimination to provide the (Z)-alkene product and regenerate a metal complex in the Nb(III) oxidation state. Support for the proposed mechanism is derived from (i) the dependence of the product selectivity on the relative concentrations of CO and H 2, (ii) the isolation of complexes closely related to those proposed to be part of the catalytic cycle, (iii) H/D crossover experiments, and (iv) DFT studies of multiple possible reaction pathways.

Original languageEnglish (US)
Pages (from-to)14904-14907
Number of pages4
JournalJournal of the American Chemical Society
Volume133
Issue number38
DOIs
StatePublished - Sep 28 2011
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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