Theoretical study on structures, stability, and bonding of Ng-inserted nitrogen-group fluorides FNgMFn (Ng = Kr, Xe; M = P, As, Sb; n = 2, 4)

Abstract

Although numerous noble-gas compounds with hydrogen, oxygen, and carbon have been characterized, their bonding with nitrogen-group elements remains scarcely explored. In particular, the structures and bonding nature of FNgMFn (Ng = Kr, Xe; M = P, As, Sb; n = 2, 4) have not been systematically investigated. In this work, a comprehensive theoretical study of these Ng-inserted fluorides was conducted using density functional theory combined with high-level CCSD(T) calculations. The results show that FNgMF2 adopts a Cs geometry, whereas FNgMF4 prefers either C2v or C3v symmetry, with the newly identified C2v conformer—reported here for the first time—being lower in energy than the previously studied C3v structure. Moreover, the present work extends the investigation to the As and Sb analogs, which have not been reported previously. Dissociation and transition-state analyses indicate that these species are thermodynamically stable against dimeric and trimeric fragmentation yet metastable toward direct dissociation into Ng + MFn+1, with kinetic barriers of 14–45 kcal/mol. Population and AIM analyses reveal that the Ng–M bonds are predominantly covalent and strengthen from Kr to Xe, whereas the F–Ng bonds are mainly ionic with minor covalent contributions. These findings provide new insights into the bonding characteristics and stability of Ng-inserted nitrogen-group fluorides and extend the understanding of noble-gas chemistry toward heavier p-block elements.