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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, reacts with much higher efficiency than does kinetically excited Cr+. FeO+ reacts with NH3 to generate FeNH+ with loss of HjO. Thermochemical studies of VNH+ and FeNH+ involving ion-molecule reactions indicate values of D°(V+-NH) = 101 ± 7 kcal/mol and £)°(Fe+-NH) = 54 ± 14 kcal/mol, the latter value in accord with £>°(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

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We report here on the synthesis and passivation of small (20-30 nm) aluminum nanoparticles using alkyl-substituted epoxides as capping agents. FTIR and 13C NMR spectroscopy indicate that the epoxides polymerize to form a polyether cap on the surfaces of the aluminum nanoparticles. Nanoparticles capped with epoxyhexane and epoxydodecane are stable in air, but particles capped with epoxyisobutane are pyrophoric. TEM images show spherical Al particles. Powder X-ray diffraction shows the presence of crystalline Al. Titrimetric analysis of the core-shell nanostructures in air reveals that 96% of the total aluminum present is active (unoxidized) aluminum.

The partitioning of reaction exothermicity into relative translational energy of the products of gas-phase S, 2 (F-+ CH,CI) and nucleophilic aromatic substitution (F-+ C,H,CI) reactions has been investigated using kinetic energy release Fourier transform ion cyclotron resonance spectroscopy. The chloride product ion is observed to be highly translationally excited for the SN2 reaction, indicating a cold internal energy distribution for the products. For the chlorobenzene reaction the products are not generated with large translational energies The results are compared with a statistical model. Ion-intensity profiles for the CH,CI reaction deviate significantly from the statistical model whereas the chlorobenzene results are consistent with this model. The kinetic energy release for the CH,CI reaction is compared with energy-disposal results for the photodissociation and dissociative electron-attachment processes of halomethanes. In all three cases a node in the molecular orbital between the carbon atom and the departing halogen results in a repulsive energy release. Ion-retention curves for the nucleophilic aromatic substitution reaction are consistent with the existence of a long-lived ion-dipole complex on the exit channel for this reaction.