| Guided ion beam mass spectrometry is used to investigate the kinetic energy dependence of a number of reactions of atomic transition metal ions with a variety of alkanes and other molecules. The reaction of ground state Co$sp+$, Ni$sp+$, Cu$sp+$ and Zn$sp+$ with a series of alkanes studied. Thermodynamic information is derived for ionic and neutral M-CH$sb3$ and M-H bond dissociation energies. Periodic trends in the thermochemical results are used to assess the effect of orbital occupation and electronic charge of the metal as well as the nature and polarizability of the ligand on transition metal bonding. The isotopic effects of the reactions of ground state Ca$sp+$ and Zn$sp+$ with H$sb2$, HD and D$sb2$ are examined. Ca$sp+$ is found to react by a direct mechanism while Zn$sp+$ via a pairwise interaction. These results clearly demonstrate the effect of occupation and relative energy of the 4s and 3d orbitals in determining ion reactivity and can be understood and predicted using molecular orbital concepts. The electronic state dependence of the reaction of Cr$sp+$ with methane is studied. The electronic state of Cr$sp+$ is varied by altering the ionization technique. Ground state ($sp6$S) Cr$sp+$ reacts with methane endothermically to produce CrCH$sb2sp+$, CrH$sp+$ and CrCH$sb3sp+$. Excited states ($sp4$D and possibly $sp4$G) react with higher efficiency to form the same products, while no evidence for reaction of the first excited state ($sp6$D) is observed. The lowest energy product, CrCH$sb2sp+$, has not previously been observed for the ground state reaction. The results are interpreted to indicate that reaction occurs partially via a H-Cr$sp+$-CH$sb3$ intermediate which has a quartet ground state and partially via a direct mechanism. The reactivity of the different electronic states of Cr$sp+$ can be explained using molecular orbital concepts and spin conservation. In a complementary study, the reactions of ground state Cr$sp+$ with ethane, ethylene, ethylene oxide and cyclopropane are examined yielding thermochemistry for a series of chromium species: CrCH$sp+$, CrCH$sb2sp+$, and CrCH$sb3sp+$. Other reactions examined are ground state Zn$sp+$ and Ca$sp+$ with O$sb2$, and the electronic state dependence of the reaction of Mn$sp+$ with ethane. |
