title: N-Heterocyclic Carbene Based Tri-organyl-Zn-Alkyl Cations: Synthesis, Structures, and Use in CO2Functionalization.
abstract: 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 CO2through insertion into the Zn-Me bond yielding the corresponding Zn(κ2-OAc)+cation 6+. Both cations 5+and 6+were successfully used in CO2hydrosilylation catalysis for silylformate formation.
authors.affiliation: Institut de Chimie de Strasbourg, CNRS, Université de Strasbourg, 1, rue Blaise Pascal, 67000, Strasbourg, France.
authors.forename: David
authors.initials: D
authors.lastname: Specklin
authors.affiliation: Institut de Chimie de Strasbourg, CNRS, Université de Strasbourg, 1, rue Blaise Pascal, 67000, Strasbourg, France.|LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
authors.forename: Christophe
authors.initials: C
authors.lastname: Fliedel
authors.affiliation: Institut de Chimie de Strasbourg, CNRS, Université de Strasbourg, 1, rue Blaise Pascal, 67000, Strasbourg, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Gourlaouen
authors.affiliation: Institut de Chimie de Strasbourg, CNRS, Université de Strasbourg, 1, rue Blaise Pascal, 67000, Strasbourg, France.
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Bruyere
authors.affiliation: LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
authors.forename: Teresa
authors.initials: T
authors.lastname: Avilés
authors.affiliation: Institut de Chimie de Strasbourg, CNRS, Université de Strasbourg, 1, rue Blaise Pascal, 67000, Strasbourg, France.
authors.forename: Corinne
authors.initials: C
authors.lastname: Boudon
authors.affiliation: Institut de Chimie de Strasbourg, CNRS, Université de Strasbourg, 1, rue Blaise Pascal, 67000, Strasbourg, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Ruhlmann
authors.affiliation: Institut de Chimie de Strasbourg, CNRS, Université de Strasbourg, 1, rue Blaise Pascal, 67000, Strasbourg, France.
authors.forename: Samuel
authors.identifier: http://orcid.org/0000-0001-7393-286X
authors.initials: S
authors.lastname: Dagorne
keywords: CO2 hydrosilylation; CO2 insertion; N-heterocyclic carbenes; cations; zinc