Room temperature ring expansion of N-heterocyclic carbenes and B-B bond cleavage of diboron(4) compounds

Sabrina Pietsch, Ursula Paul, Ian A. Cade, Michael J. Ingleson*, Udo Radius, Todd B. Marder

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We report the isolation and detailed structural characterization, by solid-state and solution NMR spectroscopy, of the neutral mono- and bis-NHC adducts of bis(catecholato)diboron (B2cat2). The bis-NHC adduct undergoes thermally induced rearrangement, forming a six-membered -B-C=N-C=C-N-heterocyclic ring via C-N bond cleavage and ring expansion of the NHC, whereas the mono-NHC adduct is stable. Bis(neopentylglycolato)diboron (B2neop2) is much more reactive than B2cat2 giving a ring expanded product at room temperature, demonstrating that ring expansion of NHCs can be a very facile process with significant implications for their use in catalysis. Bor-rings are anything but boring: The isolation and detailed structural characterization, by solid-state and solution NMR spectroscopy, of the neutral mono- and bis-NHC adducts of bis(catecholato)diboron (B2cat2) is reported. The bis-NHC adduct undergoes thermally induced rearrangement, forming a six-membered -B-C=N-C=C-N-heterocyclic ring via C-N bond cleavage and ring expansion of the NHC, whereas the mono-NHC adduct is stable, see scheme (B2neop2=bis(neopentylglycolato)diboron).

Original languageEnglish
Pages (from-to)9018-9021
Number of pages4
JournalChemistry - A European Journal
Volume21
Issue number25
DOIs
Publication statusE-pub ahead of print - 8 May 2015

Keywords

  • B-B bond activation
  • boron compounds
  • C-N bond cleavage
  • N-heterocyclic carbene
  • ring expansion reaction

Fingerprint Dive into the research topics of 'Room temperature ring expansion of N-heterocyclic carbenes and B-B bond cleavage of diboron(4) compounds'. Together they form a unique fingerprint.

Cite this