ScF2+ and ScHe3+: two highly-charged episodes from the gas-phase adventures of scandium

Quantum chemical calculations on the thermochemistry of gas-phase ScF2+ and ScHe3+ are reported. As the lightest possible closed-shell combinations of a transition metal with a halogen or rare gas atom, the identified species each possess noteworthy attributes. Our calculations show that ScF2+ is thermodynamically stable; its dissociation to either Sc2+ + F or Sc+ + F+ is highly endothermic. Further, ScF2+ is a plausible exothermic product of a yet-unknown class of electron-detachment reactions which can be described as associative charge doubling: viz., F+ + Sc → ScF2+ + e. The triply-charged species ScHe3+ appears to be the lightest known thermodynamically stable molecular trication.