Reversible Cleavage/Formation of the Chromium–Chromium Quintuple Bond in the Highly Regioselective Alkyne Cyclotrimerization

Yu Siang Huang, Gou Tao Huang, Yao Lun Liu, Jen-Shiang K. Yu*, Yi Chou Tsai

*Corresponding author for this work

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Herein we report the employment of the quintuply bonded dichromium amidinates [Cr{κ2-HC(N-2,6-iPr2C6H3)(N-2,6-R2C6H3)}]2 (R=iPr (1), Me (7)) as catalysts to mediate the [2+2+2] cyclotrimerization of terminal alkynes giving 1,3,5-trisubstituted benzenes. During the catalysis, the ultrashort Cr−Cr quintuple bond underwent reversible cleavage/formation, corroborated by the characterization of two inverted arene sandwich dichromium complexes (μ-η66-1,3,5-(Me3Si)3C6H3)[Cr{κ2-HC(N-2,6-iPr2C6H3)(N-2,6-R2C6H3)}]2 (R=iPr (5), Me (8)). In the presence of σ donors, such as THF and 2,4,6-Me3C6H2CN, the bridging arene 1,3,5-(Me3Si)3C6H3 in 5 and 8 was extruded and 1 and 7 were regenerated. Theoretical calculations were employed to disclose the reaction pathways of these highly regioselective [2+2+2] cylcotrimerization reactions of terminal alkynes.

Original languageEnglish
Pages (from-to)15427-15431
Number of pages5
JournalAngewandte Chemie - International Edition
Volume56
Issue number48
DOIs
StatePublished - 27 Nov 2017

Keywords

  • [2+2+2] cyclotrimerization
  • alkynes
  • chromium
  • homogeneous catalysis
  • quintuple bonds

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