A Mechanistically and Operationally Simple Route to Metal-N-Heterocyclic Carbene (NHC) Complexes

Nikolaos V Tzouras; Fady Nahra; Laura Falivene; Luigi Cavallo; Marina Saab; Kristof Van Hecke; Alba Collado; Christopher J Collett; Andrew D Smith; Catherine S J Cazin; Steven P Nolan

doi:10.1002/chem.202000564

A Mechanistically and Operationally Simple Route to Metal-N-Heterocyclic Carbene (NHC) Complexes

Chemistry. 2020 Apr 6;26(20):4515-4519. doi: 10.1002/chem.202000564. Epub 2020 Mar 12.

Authors

Affiliations

¹ Department of Chemistry and Centre for Sustainable Chemistry, Ghent University, Krijgslaan 281,S-3, 9000, Ghent, Belgium.
² Separation and Conversion Technology Unit, VITO (Flemish Institute for Technological Research), Boeretang 200, B-2400, Mol, Belgium.
³ KAUST Catalysis Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.
⁴ EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK.

PMID: 32022329
DOI: 10.1002/chem.202000564

Abstract

We have been puzzled by the involvement of weak organic and inorganic bases in the synthesis of metal-N-heterocyclic carbene (NHC) complexes. Such bases are insufficiently strong to permit the presumed required deprotonation of the azolium salt (the carbene precursor) prior to metal binding. Experimental and computational studies provide support for a base-assisted concerted process that does not require free NHC formation. The synthetic protocol was found applicable to a number of transition-metal- and main-group-centered NHC compounds and could become the synthetic route of choice to form M-NHC bonds.

Keywords: N-heterocyclic carbenes; complexes; mechanism; synthesis; weak bases.

Abstract

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