Applications of Fourier transform mass spectrometry to the characterization of selected transition metal clusters and metal-ligand systems
Abstract
Fourier transform mass spectrometry (FTMS) is applied to the exploration of ionic clusters and metal-ligand systems. These include Nb$\rm\sb4C\sb4\sp+$, Nb$\sb{\rm n}\sp+$ (n = 2-12), V$\sb8$C$\sb{12}\sp+$, and selected metal-arene ions. Gas-phase Nb$\rm\sb4C\sb4\sp+$ cluster ions are found to be reactive with oxygen, water and methanol. Nb$\rm\sb4C\sb4\sp+$ is observed to oxidatively decompose with oxygen, and to abstract OH and OCH$\sb3$ from water and methanol, respectively. Collisional activation studies on Nb$\sb4$C$\sb4\sp+$ are also described. The reactivity of ammonia with bare metal cluster ions of niobium, Nb$\sb{\rm n}\sp+$ (n = 1-12), is also investigated. With the exception of two sizes (n = 10, 12), the cluster ions are found to react with ammonia through an initial oxidative insertion into the N-H bond and a subsequent dehydrogenation. Novel N$\sb2$ containing cluster ions are formed through secondary reactions with ammonia. The bonding and structure of these ions is explored using collisional activation methods. The rate constants for the reactions of Nb$\sb{\rm n}\sp+$ with NH$\sb3,$ along with their nitrogen atom uptakes are determined for the cluster sizes studied in order to compare their relative reactivities. V$\rm\sb8C\sb{12}\sp+$ belongs to a family of especially abundant ions termed metallo-carbohedrenes, In this thesis we explore the gas-phase chemistry of V$\rm\sb8C\sb{12}\sp+$ clusters with various reagents. An interesting discovery is that V$\rm\sb8C\sb{12}\sp+$ oxidatively decomposes in oxygen. Furthermore, our work provides new data supporting a theoretically proposed low energy structure for metallo-carbohedrenes. Finally, the photodissociation of metal-arene cations is investigated to explore two dissociative pathways: dissociative charge transfer and simple fragmentation.
Degree
Ph.D.
Advisors
Freiser, Purdue University.
Subject Area
Analytical chemistry
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