Gas phase negative ion chemistry of organotransition metal complexes. (Volumes I and II)
Abstract
The reactivity, structure and thermochemistry of negative ions of organotransition metal complexes in the gas phase are examined with use of the flowing afterglow-triple quadrupole technique, with emphasis on the gas-phase oxidation reactions of these metal anions with dioxygen. Reaction kinetics and product distributions, product ion structures, oxidation mechanisms, and new thermochemical data for metal polyoxides, metal carbonyls and related metal-oxo systems are described. Oxidation of the metal center by dioxygen occurs slowly in the gas phase for the unsaturated (17-electrons or less) M(CO)$\sb{\rm n}\sp-$ and LM(CO)$\sb{\rm n}\sp-$ complexes, as well as for several M$\sb{\rm n}$(CO)$\sb{\rm m}\sp-$ clusters. In addition, oxidation of organic ligand(s) is observed in some cases. Several experimental techniques were developed for the studies described in this thesis, including energy-resolved CID and ion-molecule reactions, CID appearance energy measurements, and multiple, in situ isotope labeling. Ligand substitution reactions with SO$\sb2$ and CID and ion-molecule reactions with $\sp{18}$O-labeling metal ions were especially useful methods for characterizing the structures of the dioxygen oxidation products. Reactions of two isomeric (C$\sb4$H$\sb6$)Fe(CO)$\sb3$ anion complexes with a variety of small inorganic and organic molecules are described. Effects of the differing organic ligands on the reactivity of the iron center and the proton affinities of the complexes are characterized. Reactions of negative ions with (Bd)Fe(CO)$\sb3$ are also described. Ligand slippage in polyhapto organic ligands is shown to play an important role in the gas-phase reactivity of organometallic oxo complexes such as CpCoO$\sp-$ and CpMnO$\sb2\sp-$ toward Bronsted acids. The oxidizing power of transition metalates such as permanganate and vanadate anions is examined and found to be quite different from that in the condensed phase. A series of transition metal-carbonyl bond energies are determined from CID appearance energy measurements. Appearance energies for CO-loss from binary metal carbonyl anions of the first row and group 6 metals are shown to be good estimates of individual metal-carbonyl bond dissociation energies. Trends in the measured and derived M-CO bond energies are discussed in terms of the electronic configurations of metal carbonyl fragments.
Degree
Ph.D.
Advisors
Squires, Purdue University.
Subject Area
Chemistry|Chemistry
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