Direct Access to IMesF and IMesF2 by Electrophilic Fluorination of Abnormal N-Heterocyclic Carbenes
Year: 2019
Type: article
Abstract: The incorporation of fluorine atoms into the N-heterocyclic carbene (NHC) ligand backbone in a Mn(I) complex [CpMn(CO) 2 (IMes)] was achieved via a sequence of the C–H bond deprotonation and electrophilic fluorination of the anionic abnormal carbene moiety with N -fluorobenzenesulfonimide. The demetallation of resulting complexes [CpMn(CO) 2 (IMes F 1-2 )] with triflic acid afforded the imidazolium salts IMes F 1-2 ·HOTf, the precursors of the corresponding fluorinated NHCs. Interestingly, the IMes F 2 ligand was found to be more electron-donating than its well-known analogue IMes Cl 2 notwithstanding the higher electronegativity of fluorine atoms. A systematic experimental and density functional theory study of this NHC series allowed us to fully rationalize this unexpected behavior, revealing that the weaker σ-donation of IMes F 2 is compensated by its lower π-accepting properties due to the strong mesomeric +M effect of the fluorine substituents.
Source: Organometallics
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2943666088