Gas-Phase Reactions of Transition-Metal Ions with Molecular Oxygen:  Room-Temperature Kinetics and Periodicities in Reactivity

Abstract

An Inductively-Coupled Plasma/Selected-Ion Flow Tube (ICP/SIFT) tandem mass spectrometer has been employed in a systematic survey of room-temperature reactions of O 2 with 29 transition-metal ions. 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. Rate coefficients were measured for the reactions of first-row atomic ions from Sc + to Zn + , of second-row atomic ions from Y + to Cd + (excluding Tc + ) and of third-row atomic ions from La + to Hg + . Both O-atom abstraction and O 2 addition were observed as primary reaction channels. Periodicities in reactivity are identified and are compared with periodicities in the O-atom affinity of the atomic ion. O-atom abstraction was observed to be efficient when exothermic and inefficient when endothermic. NbO + , MoO + , TaO + , and WO + reacted further in a second O-atom transfer reaction with O 2 . ReO 2 + produced by direct addition of O 2 to Re + reacted further by both O-atom abstraction and O 2 addition. Sequential O 2 addition was observed to produce the higher oxides: MO 3 + (M ) Ti, V, Y, Zr, Hf, Os), MO 4 + (M ) Cr, Fe, Co, Ni, Cu, Nb, Mo, Ru, Rh, Hf, Ta, W, Re, Os, Ir, Pt, Au), MO 5 + (M ) V, Re, Os), MO 6 + (M ) Nb, W, Re) and MO 7 + (M ) V). Novel termolecular reactions second-order in oxygen were identified for Os + and ZrO + at high oxygen concentrations to produce O 2 + and OsO + from Os + and a neutral metal oxide from Zr + .

Oxygenation Mechanism of Ions in Dynamic Reaction Cell ICP-MS

“…When an element of the fifth period was included in a target system, another calculation model, less precise than the DFT, was used for calculation of the energies of the whole reaction even though the energy of oxygen could be calculated precisely by DFT. Published thermochemistry data [26][27][28][29]44 are shown together with the results in order to validate the calculations.…”

“…[26][27][28][29] Although these recent discussions of reaction cell mechanisms might be thought sufficient, there is a lack of consideration of reaction systems and reaction routes and a reliance on reference data rather than calculation of data specific to the systems under investigation. In addition, although ions are detected in ICP-MS analysis, there is a lack of thermal energy data for the ions.…”

Comment on “Role of (NO)2 Dimer in Reactions of Fe+ with NO and NO2 Studied by ICP-SIFT Mass Spectrometry”

“…3 Bohme 2013 argues the plausibility of (5)-(6) by citing analogous reactions reported by their group involving NO 2 and O 2 . 4,5 Our argument against the three-body mechanism for Fe + + NO is based on the time scale of the reaction specific to that system, depending on the vibrational and rotational frequencies and, significantly, on the dissociation energy of the complex. Os + -O 2 is bound by ~5eV, 6 which is a value given in our original paper that would make Fe + -NO stable enough for the termolecular mechanism to proceed.…”

“…Indeed, stable OsO 2 + is observed. 4 (Metal-NO 2 ) + complexes are characterized by more low energy modes than those for (Metal-NO) + ones and may be more stable. Both effects result in an upper limit on the threebody mechanism that is several orders of magnitude higher than that for the termolecular NO mechanism.…”

Classification of Chemical Elements in the Reaction Cell of ICP-MS Based on the Affinities with Sulfur, Oxygen, and Fluorine

“…Reaction cell technique offers an effective approach for the separation of spectral interferences in the measurement by ICP-MS. 15 In order to achieve specific separations of various spectral interferences, some kinds of gases had been explored as the reaction gas in the reaction cell of ICP-MS, including H 2 , O 2 , NH 3 , CH 3 F, N 2 H 6 , N 2 O, CO, NO, and SF 6 . 5 A systematic investigation of the ion-molecule reactions in the reaction cell will provide useful information for the development of a method for separating spectral interferences.…”