Gas-phase reactions of nitric oxide with atomic lanthanide cations: Room-temperature kinetics and periodicity in reactivity

An inductively coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer has been employed in a systematic survey of the room-temperature kinetics of reactions of NO with 13 atomic lanthanide cations from Ce+ to Lu+ (excluding Pm+). The atomic ions are produced at ca. 5500 K in an ICP source and are allowed to decay radiatively and to thermalize by collisions with Ar and He atoms prior to reaction in helium buffer gas at 0.35 ± 0.01 Torr and 295 ± 2 K. All lanthanide cations were observed to exhibit some reactivity towards NO, almost exclusively resulting in LnO+ formation. Reactions were observed that are both first and second order in NO. Periodic trends in the measured reaction efficiencies for direct exothermic O atom transfer correlate with trends in the energy required to promote an electron in Ln+ to achieve either a d1s1 or a d2 excited electronic configuration in which two non-f-electrons are available for bonding. No such correlation is apparent for the remaining reactions.