Strong carbon – noble gas covalent bond and fluxionality in hypercoordinate compounds.

Thermodynamic, kinetic, and chemical bonding analysis at the coupled cluster level has been carried out for a series of hypercoordinated carbon compounds with formula CH₄Ng²⁺ (Ng = He–Rn). Results show that these compounds could be stable at room temperature and Born–Oppenheimer molecular dynamics simulations (BOMD) in conjunction with activation energies indicate high kinetic stability. In addition, all chemical bonding descriptors agree with a strong C–Ng covalent bond and a bonding pattern similar to that of CH₅⁺. Finally, BOMD simulations showed that these compounds are fluxional, with a continuous formation/breaking of H–H and C–H bonds. To the best of the authors' knowledge, these results represent the first series of fluxional compounds possessing a covalent bond between a main group element and a noble gas atom. [ABSTRACT FROM AUTHOR]