Iron cation catalyzed reduction of N2O by CO: gas-phase temperature dependent kinetics

Abstract

The ion-molecule reactions Fe(+) + N2O → FeO(+) + N2 and FeO(+) + CO → Fe(+) + CO2, which catalyze the reaction CO + N2O → CO2 + N2, have been studied over the temperature range 120-700 K using a variable temperature selected ion flow tube apparatus. Values of the rate constants for the former two reactions were experimentally derived as k2 (10(-11) cm(3) s(-1)) = 2.0(±0.3) (T/300)(-1.5(±0.2)) + 6.3(±0.9) exp(-515(±77)/T) and k3 (10(-10) cm(3) s(-1)) = 3.1(±0.1) (T/300)(-0.9(±0.1)). Characterizing the energy parameters of the reactions by density functional theory at the B3LYP/TZVP level, the rate constants are modeled, accounting for the intermediate formation of complexes. The reactions are characterized by nonstatistical intrinsic dynamics and rotation-dependent competition between forward and backward fluxes. For Fe(+) + N2O, sextet-quartet switching of the potential energy surfaces is quantified. The rate constant for the clustering reaction FeO(+) + N2O + He → FeO(N2O)(+) + He was also measured, being k4 (10(-27) cm(6) s(-1)) = 1.1(±0.1) (T/300)(-2.5(±0.1)) in the low pressure limit, and analyzed in terms of unimolecular rate theory.

Spin-inversion and spin-selection in the reactions FeO+ + H2 and Fe+ + N2O

“…The wide variety of reaction times and He densities employed allowed for the determination of a third order rate constant of 1.8 (AE0.3) Â 10 À27 cm 6 molecule À2 s À1 for the initial N 2 O association, in reasonable agreement with our previous measurements. 16 Additionally, reaction of these clusters with H 2 to directly reproduce Fe + was allowed and found to have no bearing on the present results, with an effective rate constant r10 À13 cm 3 molecule À1 s À1 . The Monte Carlo plots shown in this work include the contributions of this chemistry.…”

“…The plot shows that the rate constants are well defined and separate, with the quartet rate constant smaller than that for the sextet. The most probable rate constant, k 2b = 2.3 (+0.3/À0.8) Â 10 À11 cm 3 molecule À1 s À1 , is surprisingly smaller than that for the reaction of 6 Fe + , being 16 k 2a = 3.2 (AE0.5) Â 10 À11 cm 3 molecule À1 s À1 . That is why the data curve upwards more than the single state model.…”

“…27 In addition to the reactions shown in scheme (3), other reactions were included to test the sensitivity of the present conclusions. FeO + is known 16 to cluster with N 2 O up to a coordination number of 3. The wide variety of reaction times and He densities employed allowed for the determination of a third order rate constant of 1.8 (AE0.3) Â 10 À27 cm 6 molecule À2 s À1 for the initial N 2 O association, in reasonable agreement with our previous measurements.…”

“…In earlier work 16 we have extended measurements of the temperature dependence of the rate constant of the reaction of Fe + with N 2 O and analyzed the results by a non-statistical rate model. Given the unique temperature dependence observed, significant effort went into verifying only a ground state contribution to the results.…”

Cryokinetics and spin quenching in the N2 adsorption onto rhodium cluster cations

“…It is a recently emphasised question how coupled electronic surfaces enable metal ligand interactions and reactions through changes of spin multiplicities [52]. Most notably J. Troe and co-workers analysed the reaction kinetics of such nonadiabatic processes involving Fe + + NO, N 2 O, NO 2 , and FeO + + CH 4 , H 2 , CO, NO [53][54][55][56][57][58].…”