Application of laser desorption-Fourier transform mass spectrometry to the study of small singly and doubly charged gas phase transition metal ionic species
Abstract
A wide variety of small gas-phase singly and doubly charged transition-metal ionic species were studied by laser desorption-Fourier transform mass spectrometry. The attachment of a ligand to a bare metal ion center can have a significant effect on the reactivity of the metal center. A simple $\pi$ ligand, such as an arene, an alkylnitrile, or an alkene, slows down the reaction of Fe$\sp+$ with propane significantly. Fe$\sp+$-cyclopentadiene easily rearranges into hydridocyclopentadienyliron, making its chemistry much different from that of Fe$\sp+$. Cyclopentadienylallyliron ion is formed from its reaction with propane. The reaction exothermicity can reside with the product ion and affects its subsequent kinetics. The reactions of Fe$\sp+$-benzyne with alkenes ranging from C$\sb2$ to C$\sb4$ change significantly with the alkene size. It is not clear whether such reactions are initiated by the metal center or simply proceed between the ligand and the incoming alkene molecule. Fe$\sp+$-alkene ions react with chlorobenzene via active participation of the alkene ligand, resulting in phenylation of the alkene ligand. The chemistry of Fe$\sb2\sp+$-benzyne is different from that of either Fe$\sb2\sp+$ or FeC$\sb6$H$\sb4\sp+$. ScC$\sb6$H$\sb4\sp+$ is reactive with a wide variety of species, including several oxygen-containing compounds, alkenes, and alkanes. The reaction patterns of ScC$\sb6$H$\sb4\sp+$ with hydrocarbons are different from that of Sc$\sp+$. YCH$\sb3\sp+$ undergoes $\sigma$-bond metathesis with activated C-H bonds, including the benzyl-hydrogen bonds in toluene and allylic C-H bonds of alkenes. Such a reaction pathway is favored over migratory insertion into the Y$\sp+$-CH$\sb3$ bond by C=C double bonds of simple alkenes. LaFe$\sp{2+}$ and YFe$\sp{2+}$ provide the first examples of gas phase doubly charged heterodinuclear cluster ions stable on the order of seconds. Recent theoretical calculations suggest that such stability is kinetic and not themochemical in nature. Both LaFe$\sp{2+}$ and YFe$\sp{2+}$ are reactive with simple alkanes.
Degree
Ph.D.
Advisors
Freiser, Purdue University.
Subject Area
Chemistry
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