The room-temperature reactions of nitric oxide with 46 atomic cations have been surveyed systematically across and down the periodic table using an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. Rate coefficients and product distributions were measured for the reactions of first-row cations from K+ to Se+, of second-row cations from Rb+ to Te+ (excluding Tc+), and of third-row cations from Cs+ to Bi+. Reactions both first and second order in NO were identified. The observed bimolecular reactions were thermodynamically controlled. Efficient exothermic electron transfer was observed with Zn+, As+, Se+, Au+, and Hg+. Bimolecular O-atom transfer was observed with Sc+, Ti+, Y+, Zr+, Nb+, La+, Hf+, Ta+, and W+. Of the remaining 32 atomic ions, all but 8 react in novel termolecular reactions second order in NO to produce NO+ and the metal-nitrosyl molecule, the metal-monoxide cation and nitrous oxide, and/or the metal-nitrosyl cation. K+, Rb+, Cs+, Ga+, In+, Tl+, Pb+, and Bi+ are totally unreactive. Further reactions with NO produce the dioxide cations CaO2+, TiO2+, VO2+, CrO2+, SrO2+, ZrO2+, NbO2+, RuO2+, BaO2+, HfO2+, TaO2+, WO2+, ReO2+, and OsO2+ and the still higher order oxides WO3+, ReO3+, and ReO4+. NO ligation was observed in the formation of CaO+(NO), ScO+(NO), TiO+(NO), VO+(NO)(1-3), VO2+(NO)(1-3), SrO+(NO), SrO2+(NO)1,2, RuO+(NO)(1-3), RuO2+(NO)1,2, OsO+(NO)(1-3), and IrO+(NO). The reported reactivities for bare atomic ions provide a benchmark for reactivities of ligated atomic ions and point to possible second-order NO chemistry in biometallic and metal-surface environments leading to the conversion of NO to N2O and the production of metal-nitrosyl molecules.

Catalytic conversion of harmful gases, such as the oxides of nitrogen produced in fossil-fuel combustion into nitrogen and carbon dioxide, is of utmost importance, both environmentally and economically. CO was one of the first gases investigated for eliminating NO from automobile exhaust gas: the reaction of NO with CO [Eq. (1)] is one of the mostimportant reactions occurring in automotive catalytic converters where both reactants are undesirable pollutants.[1]Base-metal oxides, mixed metal-oxide compounds such as perovskites, supported metal catalysts, metal zeolites, and alloys have all been investigated as heterogeneous catalysts for this reaction, which does not occur directly in the gas phase at room temperature to any measurable extent.[1] For example, copper in the + 2 oxidation state has been found to be active both as a base-metal-oxide catalyst and in a metalsupported or perovskite form.We report here the first example of homogeneous catalysis by the reaction described in Equation (1), which occurs in the gas phase with atomic transition-metal cations serving as catalysts. The catalysis occurs in two steps in which NO is first reduced to N 2 O. An analogous three-step catalytic reduction of NO 2 , in which NO 2 is first reduced to NO, was also discovered.The overall catalytic scheme that was established in the study reported here consists of the three catalytic cycles shown in Figure 1. These three cycles were characterized with laboratory measurements of reactions of each of the three nitrogen oxides NO 2 , NO, and N 2 O with up to 29 different transition-metal cations M + [Eqs. (2)- (4)]:

No abstract

Catalytic conversion of harmful gases, such as the oxides of nitrogen produced in fossil-fuel combustion into nitrogen and carbon dioxide, is of utmost importance, both environmentally and economically. CO was one of the first gases investigated for eliminating NO from automobile exhaust gas: the reaction of NO with CO [Eq. (1)] is one of the mostimportant reactions occurring in automotive catalytic converters where both reactants are undesirable pollutants.[1]Base-metal oxides, mixed metal-oxide compounds such as perovskites, supported metal catalysts, metal zeolites, and alloys have all been investigated as heterogeneous catalysts for this reaction, which does not occur directly in the gas phase at room temperature to any measurable extent.[1] For example, copper in the + 2 oxidation state has been found to be active both as a base-metal-oxide catalyst and in a metalsupported or perovskite form.We report here the first example of homogeneous catalysis by the reaction described in Equation (1), which occurs in the gas phase with atomic transition-metal cations serving as catalysts. The catalysis occurs in two steps in which NO is first reduced to N 2 O. An analogous three-step catalytic reduction of NO 2 , in which NO 2 is first reduced to NO, was also discovered.The overall catalytic scheme that was established in the study reported here consists of the three catalytic cycles shown in Figure 1. These three cycles were characterized with laboratory measurements of reactions of each of the three nitrogen oxides NO 2 , NO, and N 2 O with up to 29 different transition-metal cations M + [Eqs. (2)- (4)]:

Results are reported for experimental measurements of the room-temperature chemical reactions between ground-state Hg*+ ions and 16 important environmental and biological gases: SF6, CO, CO2, N2O, D2O, CH4, CH3F, O2, CH3Cl, OCS, CS2, NH3, C6F6, NO2, NO*, and C6H6. The inductively coupled plasma/selected-ion flow tube tandem mass spectrometer used for these measurements has provided both rate and equilibrium constants. Efficient electron transfer (>19%) is observed with CS2, NH3, C6F6, NO2, NO*, and C6H6, molecular addition occurs with D2O, CH4, CH3F, CH3Cl, and OCS, and SF6, CO, CO2, N2O, and O2 showed no measurable reactivity with Hg*+. Theory is used to explore the stabilities and structures of both the observed and unobserved molecular adducts of Hg*+, and reasonable agreement is obtained with experimental observations, given the uncertainties of the theory and experiments. A correlation is reported between the Hg*+ and proton affinities of the ligands investigated. Solvation of Hg*+ with formic acid was observed to increase the rate of electron transfer from NO* by more than 20%.