Do Planar Tetracoordinate Fluorine Atoms Exist? Revisiting a Theoretical Prediction

Abstract

We re-examined the existence of planar tetracoordinateF (ptF)atoms, which was proposed recently by using high-level ab initio methodssuch as coupled-cluster singles and doubles with perturbative triples(CCSD(T)) with large basis sets. Our calculations indicate that theplanar structures of FIn4 (+) (D (4h)), FTl4 (+) (D (4h)), FGaIn3 (+) (C (2V)), FIn2Tl2 (+) (D (2h)), FIn3Tl+ (C (2V)), and FInTl3 (+) (C (2V)) are not the minimum energy states; by contrast, theyare transition states. Density functional theory calculations overestimatethe size of the cavity formed by the four peripheral atoms, leadingto erroneous conclusions regarding the existence of ptF atoms. Ouranalysis suggests that the preference for non-planar structures inthe six cations studied is not due to the pseudo Jahn-Tellereffect. Additionally, spin-orbit coupling does not alter themain conclusion that the ptF atom does not exist. If sufficientlylarge cavity formation by group 13 elements to accommodate the centralF(-) ion is guaranteed, then the existence of ptFatoms is plausible.