Synergic Deprotonation Generates Alkali-Metal Salts of Tethered Fluorenide-NHC Ligands Co-Complexed to Alkali-Metal Amides

Abstract

Synergic combinations of alkali-metal hydrocarbyl/amide reagents were used to synthesise saturated N-heterocyclic carbene (NHC) ligands tethered to a fluorenide anion through deprotonation of a spirocyclic precursor, whereas conventional bases were not successful. The Li₂ derivatives displayed a bridging amide between two Li atoms within the fluorenide-NHC pocket, whereas the Na₂ and K₂ analogues displayed extended solid-state structures with the fluorenide-NHC ligand chelating one alkali metal centre.

Keywords: alkali metals; bimetallic base; carbene ligands; metalation.