34755-45-8Relevant articles and documents
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
Buckner, Steven W.,Gord, James R.,Freiser Ben S.
, p. 6606 - 6612 (1988)
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.
