Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographies.

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 61-64.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Stephen F. Martin. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2002. / Includes bibliographical references. Also available on microfiche.

The carbonylation of methanol catalysed by Group 9 metals is the principle industrial route to acetic acid. It has been one of the most important applications of homogeneous catalysts for thirty years. In that time the preferred catalytic species has descended the group from cobalt, through rhodium, and recently to iridium with the introduction of B.P. Chemical's Cativa process. Rhodium and iridium are precious metals, it would be advantageous to develop a catalytic system which does not depend on a rare metal. One way this could be achieved is by improving cobalt catalysed carbonylation. Work has concentrated on the ability of the cyclopentadienyl, pentamethylcyclopentadienyl and triethyl phosphine ligands to promote cobalt catalysts. Several novel cobalt catalysts and one novel rhodium catalyst have been discovered for the carbonylation of methanol to methyl acetate. CH3OH + ROH Co/Catalyst-→ CH3COOR + H2O At 120°C using [Cp*Co(CO)2] and Pet3 as catalyst precursors rates of methanol carbonylation have been achieved which are, to our knowledge, far greater than any previously reported for cobalt catalysts. The initial rate of carbonylation compares favourably with that of rhodium based systems. High Pressure Infrared Spectroscopy has been utilised extensively as a tool for investigating the solution behaviour of the novel catalyst precursors [CpCo(CO)PMe2ph], [CpCo(CO)2], [Cp*Co(CO)2] and [Cp*Rh(C0)2].

[RhCl(CO)(Pet3)2] or a compound prepared in situ from [Rh2(OAc)4] and Pet3 have been shown to be active catalysts for the carbonylation of allylic halides under relatively mild conditions. This reaction is of considerable significance since it is a rare example of a system in which C-Cl bonds can be carbonylated using a rhodiun based system. The reaction occurs in the absence of added base and there is little isomerisation of the double bond when forming the ester. Using either 3-chlorobut-l-ene or l-clilorobut-2-ene, the products obtained are identical. The oxidative addition of 1-clilorobut-2-ene occurs via an S[sub]N2 mechanism whereas an S[sub]N2' mechanism operates for the 3-chlorobut-1-ene because of the steric effects of the methyl group adjacent to the chlorine. Extensive mechanistic studies have been carried out and many of the intermediates have been characterised using multinuclear variable temperature, high pressure NMR and high pressure IR as well as isolation of the intermediates. The oxidative addition and migratory insertion complexes have both been characterised using the above methods enabling the mechanism of the carbonylation reaction to be elucidated. Supercritical carbon dioxide has been used to replace ethanol as the solvent to increase the concentration of carbon monoxide in the solution in an attempt to achieve a greater ester:ether ratio. However, catalyst solubility was a problem in these reactions. In an attempt to solve this problem phosphine ligands containing organo-fluorine groups were investigated. With the fluorinated groups present on the phosphine ligands the rhodium complex was soluble in the supercritical carbon dioxide. The ethylene spacer between the phosphorus atom and the fluorinated chain ensured that the fluorinated phosphines had a similar basicity to that of triethylphosphine. However, only low yields were obtained from the catalytic reactions possibly due the failure of the supercritical carbon dioxide to stabilise the ionic intermediates of the oxidative addition reaction.

The use of the catalyst precursors rhodium acetate [Rh2(OAc)4], carbon monoxide and triethyl phosphine in an alcoholic solvent forms a catalytic species capable of the double carbonylation of diiodomethane. When this reaction is carried out in ethanol, the major products are diethylmalonate (DEM) and ethyl iodide. CH2l2 + 2CO + 2EtOH □(→┴([Rh^2(OAc)4 ]/ PEt3/CO ) ) CH2(COOEt)2 +2Hl The ethyl iodide is formed by the reaction of EtOH with HI, presumably forming equal amounts of water. The other, minor, products of this reaction were diethoxymethane (CH2(OEt)2), ethyl propanoate (CH3CO2Et) with a trace of ethyl acetate (CH3CO2Et). The diethoxymethane is formed by the ethanolysis of the substrate and the ethyl propanoate may be from the carbonylation of ethyl iodide formed in situ. The source of the ethyl acetate has been shown to be ketene, a metal complex thereof being shown to be the singly carbonylated intermediate between diiodomethane and DEM. Possibly the most notable feature of this catalytic reaction is that it occurs in the absence of added base. A review of all the double carbonylation reactions reported to date reveals this catalytic system to be unique in this respect (see chapter one). It is the solvent, EtOH, which acts as the sink for HI in this system and this accounts for the high yields of EtI. A thorough study of the mechanism of this reaction has led to the proposal of the mechanistic cycle shown in figure A. The most salient feature of this mechanism is the proposal of a metallo ketene intermediate. Evidence for the involvement of a metallo ketene complex in this reaction comes from the study of the attempted synthesis of the iodoacyl intermediate 3d and a deuterium labelling study (chapter three).

No description available.

No description available.

No description available.