FK<sub>4</sub>H<sub>4</sub><sup>–</sup>: Planar Tetracoordinate Fluorine Stabilized by Multicenter Ionic Bonding
Yanxia Jin, Li-Xia Bai, Jin‐Chang Guo
Abstract
Planar tetracoordinate fluorine (ptF) species are very exotic and scarce due to high electronegativity of fluorine. Herein we report the ternary square ptF cluster, D 4 h FK 4 H 4 –, which is composed of a F center, a square K 4 ring, and four outer H bridges. It is a true global minimum (GM) structure and possesses good dynamic stability. Bonding analyses indicate that there are four lone pairs for the central F atom, along with four K–H–K three-center two-electron (3c–2e) σ bonds for the peripheral K 4 H 4 ligand ring. The stability of ptF is dominated by multicenter ionic bonds rather than the supposed σ aromaticity of the system. Excitingly, it is a pseudohalogen anion with the VDE 3.57 eV at the CCSD(T) level. The merge of ptF with pseudohalogen anion character makes the FK 4 H 4 – cluster an exotic species, which will motivate theoretical and experimental studies on novel ptF species as well as superhalogens.