Rational design of highly active "hybrid" phosphine-phosphinite pincer iridium catalysts for alkane metathesis

Agnieszka J. Nawara-Hultzsch, Jason D. Hackenberg, Benudhar Punji, Carolyn Supplee, Thomas J. Emge, Brad C. Bailey, Richard R. Schrock, Maurice Brookhart, Alan S. Goldman

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Abstract

Both the bisphosphine and bisphosphinite pincer complexes ( tBu4PCP)IrH2 and (tBu4POCOP)IrH2 can cocatalyze alkane metathesis in tandem with olefin metathesis catalysts, but the two complexes have different resting states during catalysis, suggesting that different steps are turnover-limiting in each case. This led to the hypothesis that a complex with intermediate properties would be catalytically more active than either of these two species. Accordingly, "hybrid" phosphine-phosphinite pincer ligands (PCOP) and the corresponding iridium complexes were synthesized (3c-e). In tandem with olefin-metathesis catalyst MoF12, (tBu4PCOP)IrH2 displays significantly higher activity for the metathesis of n-hexane than does (tBu4PCP)IrH 2 or (tBu4POCOP)IrH2. (tBu2PCOP iPr2)IrH4 (3d) is even more active (>30-fold more active than (tBu4POCOP)IrH2) and affords nearly 4.6 M alkane products after 8 h at 125 C.

Original languageEnglish
Pages (from-to)2505-2514
Number of pages10
JournalACS Catalysis
Volume3
Issue number11
DOIs
Publication statusPublished - Nov 1 2013

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Keywords

  • alkane metathesis
  • dehydrogenation
  • homogeneous catalysis
  • iridium
  • pincer complexes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

Cite this

Nawara-Hultzsch, A. J., Hackenberg, J. D., Punji, B., Supplee, C., Emge, T. J., Bailey, B. C., Schrock, R. R., Brookhart, M., & Goldman, A. S. (2013). Rational design of highly active "hybrid" phosphine-phosphinite pincer iridium catalysts for alkane metathesis. ACS Catalysis, 3(11), 2505-2514. https://doi.org/10.1021/cs400624c