FK₄H₄^-: Planar Tetracoordinate Fluorine Stabilized by Multicenter Ionic Bonding

Area of Science:

• Inorganic Chemistry
• Theoretical Chemistry
• Materials Science

Background:

• Planar tetracoordinate fluorine (ptF) species are rare due to fluorine's high electronegativity.
• The existence of stable ptF structures challenges conventional chemical bonding theories.

Purpose of the Study:

• To report the discovery and characterization of a novel ternary square ptF cluster, FK4H4-.
• To investigate the structural stability, bonding nature, and electronic properties of this unique species.

Main Methods:

• Computational chemistry methods, including Density Functional Theory (DFT) and Coupled Cluster (CCSD(T)) calculations.
• Analysis of bonding characteristics, including lone pair electron distribution and multicenter bonding.

Main Results:

• Identification of FK4H4- as a true global minimum (GM) structure with significant dynamic stability.
• Detailed bonding analysis revealed multicenter ionic bonds and K-H-K three-center two-electron (3c-2e) σ bonds, rather than σ aromaticity.
• The cluster exhibits characteristics of a pseudohalogen anion with a Vertical Detachment Energy (VDE) of 3.57 eV.

Conclusions:

• The FK4H4- cluster represents a significant advancement in the study of ptF species.
• Its unique combination of ptF structure and pseudohalogen anion character makes it an exotic species of high theoretical and experimental interest.
• This discovery is expected to stimulate further research into novel ptF compounds and superhalogens.