  Eleven possible candidates for compounds of pentavalent praseodymium were
investigated with relativistic density functional theory using the B3LYP
functional with ZORA scalar relativistic correction and including spin orbit
coupling effects. Two of those candidates had previously been synthesized and
another two of them were previously theoretically predicted. Three new species
were proposed here as possible candidates for the compounds of Pr in its fifth
oxidation state: PrF4+, PrO2F2- and PrOF2+. The main technical obstacle in
synthesizing these ions is their high reactivity due to large electron
affinity; decomposition via bimolecular reaction pathways and low energy of
excitation to the triplet state constitute other stability limiting factors.
