Imidazolylidene Cu(II) complexes: synthesis using imidazolium carboxylate precursors and structure rearrangement pathways

S�gaud, Nathalie; McMaster, Jonathan; van Koten, Gerard; Albrecht, Martin

Abstract

Copper(II) complexes of type (NHC)CuX2 (X = OAc, Cl, Br, BF4, NO3) bearing monodentate N-heterocyclic carbenes (NHCs) were prepared by in situ decarboxylation of imidazolium carboxylates as a new synthetic methodology for Cu(II)-NHC complexes. In contrast to the classical deprotonation method, the decarboxylation protocol does not require anaerobic conditions and provides access to complexes with NHCs that are unstable as free carbenes such as N,N’-diisopropyl-imidazolylidene and N,N’-dimethyl-imidazolylidene. Spectroscopic evidence of the formation of the Cu‒CNHC bond is provided by UV-vis and EPR, in particular by the 44 MHz carbene hyperfine coupling constant using a 13C-labelled imidazolylidene ligand. A variation of the nature of the carbene N-substituents and the anions bound to the Cu(II) center is possible with this methodology. These variations strongly influence the stability of the complexes. Structural rearrangement and ligand reorganization was observed during recrystallisation, which are comprised of heterolytic Cu‒CNHC bond dissociation for unstable NHC ligands as well as homolytic Cu‒X bond cleavage and disproportionation reactions depending on the nature of the anion X in the copper complex.

Citation

Ségaud, N., McMaster, J., van Koten, G., & Albrecht, M. (2019). Imidazolylidene Cu(II) complexes: synthesis using imidazolium carboxylate precursors and structure rearrangement pathways. Inorganic Chemistry, 58(23), 16047-16058. https://doi.org/10.1021/acs.inorgchem.9b02568

• Journal Article Type: Article
• Acceptance Date: Oct 23, 2019
• Online Publication Date: Nov 12, 2019
• Publication Date: Dec 2, 2019
• Deposit Date: Nov 11, 2019
• Publicly Available Date: Nov 13, 2020
• Journal: Inorganic Chemistry
• Print ISSN: 0020-1669
• Electronic ISSN: 1520-510X
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 58
• Issue: 23
• Pages: 16047-16058
• DOI: https://doi.org/10.1021/acs.inorgchem.9b02568
• Keywords: Physical and Theoretical Chemistry; Inorganic Chemistry
• Public URL: https://nottingham-repository.worktribe.com/output/3200009
• Publisher URL: https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b02568
• Additional Information: This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Inorganic Chemistry, copyright © American Chemical Society after peer review.To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b02568