Planar Pentacoordinate Fluorine Embedded in the Aromatic [FCu5(C10H10)2] Sandwich

Abstract

Designing an experimentally viable planar pentacoordinate fluorine (ppF) species remains challenging, although planar F©Li5F5– and F©Zn5O5– stars have recently been predicted. Here, using the stable [Cu5(C10H10)2]+ sandwich as the ligand cage, we have broken through the limitation of planar ligand rings and designed the first triple-layered ppF [FCu5(C10H10)2] sandwich complex. The ppF [FCu5(C10H10)2] sandwich possesses perfect D5h symmetry, with a FCu5 pentagon sandwiched by two large π-coordinating C10H10 rings. It exhibits good thermodynamic and kinetic stability. Chemical bonding analysis reveals that the stability of the ppF center is dominated by multicenter ionic bonding, while the ligand cage is guarded by the d−π bonding between Cu and C atoms, as well as the localized C–C, C–H, and delocalized π bonds on the C10H10 rings. Magnetic response and adaptive natural density partitioning (AdNDP) analyses reveal a unique global cylindrical aromatic character sustained by robust multicenter interlayer bonding. The current contribution not only introduced a new member to the ppF family but also provided a new “sandwich strategy” for designing planar hypercoordinate fluorine atoms.