High-activity cobalt catalysts for alkene hydroboration with electronically responsive terpyridine and α-diimine ligands

W. Neil Palmer, Tianning Diao, Iraklis Pappas, Paul J. Chirik

Research output: Contribution to journalArticlepeer-review

Abstract

Cobalt alkyl complexes bearing readily available and redox-active 2,2′:6′,2″-terpyridine and α-diimine ligands have been synthesized, and their electronic structures have been elucidated. In each case, the supporting chelate is reduced to the monoanionic, radical form that is engaged in antiferromagnetic coupling with the cobalt(II) center. Both classes of cobalt alkyls proved to be effective for the isomerization-hydroboration of sterically hindered alkenes. An α-diimine-substituted cobalt allyl complex proved exceptionally active for the reduction of hindered tri-, tetra-, and geminally substituted alkenes, representing one of the most active homogeneous catalysts known for hydroboration. With limonene, formation of an η3-allyl complex with a C-H agostic interaction was identified and accounts for the sluggish reactivity observed with diene substrates. For the terpyridine derivative, unique Markovnikov selectivity with styrene was also observed with HBPin. (Figure Presented).

Original languageEnglish (US)
Pages (from-to)622-626
Number of pages5
JournalACS Catalysis
Volume5
Issue number2
DOIs
StatePublished - Feb 6 2015

Keywords

  • Boronates
  • Catalysis
  • Cobalt
  • Hydroboration
  • Redox-active ligands

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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