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The chemistry of lanthanides (Ln=La-Lu) is dominated by the low-valent +3 or +2 oxidation state because of the chemical inertness of the valence 4f electrons. The highest known oxidation state of the whole lanthanide series is +4 for Ce, Pr, Nd, Tb, and Dy. We report the formation of the lanthanide oxide species PrO4 and PrO2 (+) complexes in the gas phase and in a solid noble-gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented Pr(V) oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in a suitable coordination environment.

The chemistry of lanthanides (Ln=La-Lu) is dominated by the low-valent +3 or +2 oxidation state because of the chemical inertness of the valence 4f electrons. The highest known oxidation state of the whole lanthanide series is +4 for Ce, Pr, Nd, Tb, and Dy. We report the formation of the lanthanide oxide species PrO4 and PrO2 (+) complexes in the gas phase and in a solid noble-gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented Pr(V) oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in a suitable coordination environment.

Calculations using density functional theory were performed to explore the mechanisms for atmospheric degradation of isopropyl methyl methylphosphonate (IMMP). The potential energy surface profiles for OH-initiated reaction of IMMP were constructed, and all possible degradation channels were considered. Rate constants were further calculated using transition state theory. It was established from these calculations that H-abstractions from alkyl groups have much lower energy barriers than substitutions of alkoxyl groups, and four possible H-abstraction channels are competitive. Investigations into the secondary reactions under the presence of O2/NO were also performed. It is shown that O2 addition, reaction of peroxide radicals with NO to form RO radicals, and removal of ·RO are the major degradation pathways for alkyl radicals. Four selected products, CH3OP(O)(CH3)OC(O)CH3, CH3OP(O)(O)CH3, (CH3)2CHOP(O)(CH3)OH, and (CH3)2CHOP(O)(CH3)OCHO, are predicted to be the major products in this study. © 2013 Wiley Periodicals, Inc.