Application of Fourier transform ion cyclotron resonance mass spectrometry to the characterization of selected transition metal imido and acetylene complexes and metal carbon clusters

The gas-phase reactivity of group 3 transition metal imido ions and metal-carbon cluster ions, and the photochemistry of selected metalacetylene ions have been studied using Fourier transform ion cyclotron resonance mass spectrometry. A variety of gas-phase techniques have been employed to probe reaction mechanisms, ion structures and thermochemistry of these systems. Due to the d$\sp0$ electronic configuration of the metal center, MNH$\sp+$ (M = Sc and Y) provide an opportunity to study alternative mechanisms of C-C and C-H activation other than the most commonly observed oxidative addition. The reactivity of these metal imido ions with simple alkenes is reported. A general reaction mechanism involving the formation of a four-centered 2-azametallacyclobutane key intermediate followed by a $\beta$-hydrogen transfer to the metal center is proposed to explain the reactions observed. Proposed mechanisms for the observed reactions are discussed in light of the condensed-phase early-transition metal cyclometallation chemistry.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI)The reactivity of Nb$\sb4$C$\sb4\sp+$ generated from the secondary reaction of Nb$\sb4\sp+$ with ethylene is investigated to provide experimental evidence for the theoretically calculated 2x2x2 cubic crystallite structure. The results are compared with the previously reported reactivity of Nb$\sb4$C$\sb4\sp+$ generated in a supersonic source by seeding the expansion gas with methane. Finally, gas-phase photodissociation of metal-acetylene ions is studied to provide experimental evidence for the trends in bonding observed in ab initio calculations. From the photoappearance thresholds of the simple cleavage product M$\sp+$, experimental bond energy values are assigned. Ion-molecule reactions and competitive CID are used to obtain complementary information