Ring-Expanded N-Heterocyclic Copper(I) Boryl Complexes: The Structures of [(6-Dipp)CuBcat], [(6-Dipp)CuBneop], and [(6-Dipp)CuBhex]

Dawid J. Babula, Rex S.C. Charman, Thomas H. Jerome, Thomas M. Horsley Downie, Mary F. Mahon, David J. Liptrot

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σ-Bond metathesis reactions between [(6-Dipp)CuOtBu] (6-Dipp=:C({Dipp}NCH2)2CH2, Dipp=2,6-iPr2−C6H3) and three diboranes gave access to three new copper(I) boryl complexes [(6-Dipp)CuBcat], [(6-Dipp)CuBneop], and [(6-Dipp)CuBhex] (cat=1,2-O2C6H4; neop=(OCH2)2C(CH3)2; hex=OC(CH3)HCH2C(CH3)2O). Whilst [(6-Dipp)CuBcat] and [(6-Dipp)CuBneop] formed rapidly in toluene, access to [(6-Dipp)CuBhex] required heating to 60 °C for days. The complexes were characterised by single-crystal X-ray crystallography which showed in all three cases that the systems were monomers and distorted-linear at the copper atom. The stability of [(6-Dipp)CuBneop] was found to be comparable to that of [(IPr*)Cu-Bneop] (IPr*=1,3-bis(2,6-(diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene); it persisted in solution for days with no sign of decomposition. [(6-Dipp)CuBhex] is a rare crystallographically characterised example of a complex containing a boryl anion supported by the hexylene glycolato ligand.

Original languageEnglish
Article numbere202300043
JournalEuropean Journal of Inorganic Chemistry
Issue number13
Early online date27 Feb 2023
Publication statusPublished - 2 May 2023

Bibliographical note

Funding Information:
DJL thanks the Royal Society for the support of a University Research Fellowship. We wish to thank the University of Bath for funding and MC for use of their analytical facilities. 2
Royal Society - URF\R1\1910

Data Availability Statement

The data that support the findings of this study are available in the supplementary material of this article.


  • boron
  • boryl anion
  • carbene ligands
  • copper
  • ring-expanded N-heterocyclic carbene

ASJC Scopus subject areas

  • Inorganic Chemistry


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