How genuine is the quadruple bond in AeF- (Ae = Be-Ba)?

Multiple bonding has fascinated chemist since its inception. Recently, genuine quadruple bond in AeF(-) (Ae = Be-Ba) has been proposed (Chem. Sci. 14 (2023) 4872-4887). The genuineness of such a quadruple bond is scrutinized here with electron localization function (ELF). ELF analysis reveals the presence of a disynptic Ae-F basin which integrates to <2.0 electrons, much lower than expected for quadruple bond. The presence of excess kinetic energy in the bonding basins makes these bonds a unique type called Charge-Shift.

Automated summary

This study examines the genuineness of a proposed quadruple bond in AeF(-) (Ae = Be-Ba) using electron localization function (ELF). The ELF analysis reveals the presence of a disynaptic Ae-F basin with electron integration much lower than expected for a quadruple bond. These bonds are classified as Charge-Shift bonds due to the excess kinetic energy in the bonding basins.