Gas-phase activation of silane, disilane and germane by actinide ions; and collision induced dissociation of metal oxide ions in TOF-MS

Abstract

Gas-phase reactions of selected actinide metal ions, An +, with silane, disilane and germane under minimally hyperthermal conditions were studied using a reflectron time-of-flight mass spectrometer (RTOF-MS). Both U + and Np + reacted with silane while Pu + was comparatively inert. The primary reactions with silane yielded the silylenes, AnSiH 2 +; secondary reactions gave AnSi 2H 4 + and AnSi 2H 2 + (An=U, Np). With disilane, single- and double-dehydrogenation by An + produced AnSi 2H 4 + and AnSi 2H 2 + for An=U and Np, while Pu + and Am + were inert. Oxo-ligation rendered plutonium reactive towards silane: UO +, NpO + and PuO + each dehydrogenated disilane to give AnOSi 2H 4 +. With germane, selected lanthanide ions, M +Ln +, were studied along with M +An +. Germylenes, MGeH 2 +, were formed for M=Th, U, Np, Pu, Ce and Tb, while Am + and Tm + were inert. Secondary products were MGe 2 + (M=Th, U, Np, Ce and Tb), ThGe 3 + and ThGe 4 +. The results are assessed in the context of the electronic structures and energetics of the actinide (and lanthanide) ions. For comparison and to confirm consistency with previous studies, a few reactions of CH 4 and C 2H 6 with actinide ions were examined. The nature of anomalous peaks at ion flight times corresponding to “tetrahydride” ions, “AnH 4,” upon introduction of both reactive and inert gases into the reaction region was examined in detail. It was concluded that these aberrant peaks were due to high-energy collision induced dissociation of actinide oxide ions, AnO +, in the first field-free region of the RTOF-MS. The identification of this dissociation phenomenon nullifies a previous report of actinide hydride ions produced by reactions of An + with ethylene oxide.