- State-Specific Reactions of Fe+(6D, 4F) with O2 and c-C2H4O: Do0(Fe+-O) and Effects of Collisional Relaxation
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Reactions with Fe+ with O2 and c-C2H4O are studied by guided ion beam techniques.State-specific reaction cross sections for production of F2O+ are presented for the 6D ground and the 4F first excited states of Fe+.In the reaction with O2, these states exhibit similar cross section energy dependences and magnitudes, in contrast to large differences noted with H2.The dissimilarities are explained in terms of spin and orbital considerations that are much less restrictive in the case of reaction with the triplet O2 molecule.With ethylene oxide, Fe+(6D) reacts endothermically to form FeO+, while Fe(4F) shows exothermic behavior.The clear difference in cross section behaviors allows a precise determination of Do0(Fe+-O)=3.53 +/- 0.06 eV.This derived value is discussed with respect to several past results.Also presented is reaction of O2 with Fe+ created by laser vaporization.A small fraction of the ions produced by this source is not completely quenched by > 1E5 collision with He.The extent of this residual electronic excitation is found to be dependent on the power of the vaporizing laser.
- Loh, S. K.,Fisher, R.,Lian, Li,Cshultz, Richard H.,Armentrout, P. B.
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- Gas-Phase Chemistry of Transition Metal-Imido and -Nitrene Ion Complexes. Oxidative Addition of N-H Bonds in NH3 and Transfer of NH from a Metal Center to an Alkene
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We report here on the gas-phase chemistry of a number of bare transition metal-nitrene and -imido ion complexes, MNH+.Group 3, 4, and 5 atomic metal ions react with NH3 at thermal energies to generate MNH+ via dehydrogenation.A reaction mechanism is proposed involving initial oxidative addition to an N-H bond, in analogy to mechanisms proposed for reactions of gaseous atomic metal ions with hydrocarbons.Cr+ reacts with NH3 via slow condensation to form CrNH3+, as do all group 6-11 atomic metal ions investigated.However, excited-state Cr+ reacts with NH3 via bond-insertion reactions to form CrNH2+ and CrNH+.An unidentified metastable electronic state of Cr+, produced by direct laser desorption of chromium foil, reats with much higher efficiency than does kinetically excited Cr+.FeO+ reacts with NH3 to generate FeNH+ with loss of H2O.Thermochemical studies of VNH+ and FeNH+ involving ion-molecule reactions indicate values of D0(V+-NH) = 101 +/- 7 kcal/mol and D0(Fe+-NH) = 54 +/- 14 kcal/mol, the latter value in accord with D0(Fe+-NH) = 61 +/- 5 kcal/mol obtained from photodissociation.The high bond strength for VNH+ indicates multiple bonding, analogous to that in the isoelectronic VO+, while the weaker bond strength for FeNH+ indicates a single bond, analogous to that in the isoelectronic FeO+.Proton-transfer experiments indicate PA(VN) = 220 +/- 4 kcal/mol from which ΔHf(VN) = 111 +/- 9 kcal/mol and D0(V-N) = 125 +/- 9 kcal/mol are obtained.VNH+ is unreactive with ethene and benzene, but FeNH+ transfers NH to ethene and benzene through metathesis and homologation reactions.A cyclic metalloaminobutane intermediate is consistent with the products of the FeNH+/ethene reaction.
- Buckner, Steven W.,Gord, James R.,Freiser Ben S.
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p. 6606 - 6612
(2007/10/02)
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