N-Heterocyclic Carbene Based Tri-organyl-Zn–Alkyl Cations: Synthesis, Structures, and Use in CO2 Functionalization

David Specklin, Christophe Fliedel, Christophe Gourlaouen, Jean Charles Bruyere, Teresa Avilés, Corinne Boudon, Laurent Ruhlmann, Samuel Dagorne

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)


Tri-organyl and tricoordinate N-heterocyclic carbene (NHC) Zn–NHC alkyl cations [(nNHC)2Zn-Me]+ (nNHC=C2-bonded-IMes/-IDipp; 3+ and 4+; IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene, IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were first synthesized and structurally characterized by ionization of the corresponding neutral precursors [(nNHC)ZnMe2] with [Ph3C][B(C6F5)4] in the presence of one equivalent of free NHC. Whereas cation [(nIMes)2Zn-Me]+ (3+) is stable, its sterically congested analogue [(nIDipp)2Zn-Me]+ (4+) readily undergoes an nNHC-to-aNHC isomerization in the presence of THF or IDipp to afford the more thermodynamically stable [(aIDipp)(nIDipp)Zn-Me]+ (aIDipp=C4-bonded IDipp, 5+), reflecting the adaptable-to-sterics coordination chemistry of these cations for improved stability. Cations 3+–5+ are the first Zn cations of the type Zn(C)(C′)(C′′)+ (C, C′, C′′=σ-donor carbyl ligand). Kinetic studies combined with DFT calculations agree with an nNHC-to-aNHC process proceeding through the initial deprotonation of 4+ (at a Zn-bonded C4-IDipp moiety) by IDipp. Unlike 3+ and 4+, the rearranged cation 5+ reacts with CO2 through insertion into the Zn–Me bond yielding the corresponding Zn(κ2-OAc)+ cation 6+. Both cations 5+ and 6+ were successfully used in CO2 hydrosilylation catalysis for silylformate formation.

Original languageEnglish
Pages (from-to)5509-5519
Number of pages11
JournalChemistry - A European Journal
Issue number23
Publication statusPublished - 1 Jan 2017


  • cations
  • CO hydrosilylation
  • CO insertion
  • N-heterocyclic carbenes
  • zinc

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