This mechanism is supported by isotopic and steric effects. Co-catalytic systems were explored for the oxidation of alcohols using sodium bromide or oxoammonium ions with the H202/MTO system. The molecular oxygen binding rate constant for a variety of Co(II)salen derivatives was explored. The rate constant was determined using flash photolysis to dissociate oxygen from the pre-made CO(III)-02· complex. A new twist to the rate constant determination of these reactions was also explored where in flash photolysis severs a cobalt-carbon bond of a Co(Ill)-alkyl complex, producing the CO(III) complex in the presence Of 02 and a radical scavenger.

Catalysis is a very interesting area of chemistry, which is currently developing at a rapid pace. A great deal of effort is being put forth by both industry and academia to make reactions faster and more productive. One method of accomplishing this is by the development of catalysts. Enzymes are an example of catalysts that are able to perform reactions on a very rapid time scale and also very specifically; a goal for every man-made catalyst. A kinetic study can also be carried out for a reaction to gain a better understanding of its mechanism and to determine what type of catalyst would assist the reaction. Kinetic studies can also help determine other factors, such as the shelf life of a chemical, or the optimum temperature for an industrial scale reaction. An area of catalysis being studied at this time is that of oxygenations. Life on this earth depends on the kinetic barriers for oxygen in its various forms. If it were not for these barriers, molecular oxygen, water, and the oxygenated materials in the land would be in a constant equilibrium. These same barriers must be overcome when performing oxygenation reactions on the laboratory or industrial scale. By performing kinetic studies and developing catalysts for these reactions, a large number of reactions can be made more economical, while making less unwanted byproducts. For this dissertation the activation by transition metal complexes of hydrogen peroxide or molecular oxygen coordination will be discussed.

Allylic alcohols were oxidized using hydrogen peroxide as an oxygen source and methyltrioxorhenium (MTO) as catalyst. Hydrogen peroxide and MTO react to form 1:1 and 2:1 rhenium peroxides, denoted as A and B, respectively. The bisperoxide species, B was the reactive form of the catalyst. The rate constants for the oxidation of the allylic alcohols were evaluated using pseudo-first-order techniques and were slower than the corresponding alkenes. An unexpected dependence of the rate constant on [H202] was found for fast-reacting substrates. A mechanism featuring H-bonding of the allylic alcohol with a peroxidic oxygen of the catalyst is proposed. Kinetic measurements with added pyridine N-oxide showed that the rate constants initially decrease with increasing pyridine N-oxide concentration, reach a minimum, and then increase, finally surpassing that of the experiment without pyridine N-oxide.

Spectroscopic studies have been used to describe the mechanism of the decomposition of hydrogen peroxide by solutions of a dimeric Cu(II) complex of a dissymetric Schiff base, [CuSALAD]2.H2O, and imidazole or methyl substituted imidazoles, B, which form monomeric CuSALADB2 complexes, in aqueous ethanol solvent. Freezing Point Depression and Vapor Pressure Lowering studies were carried out to confirm the dimeric nature of the [CuSALAD]2.H2O complex that had been previously reported. The stoichiometry of the [CuSALAD] .H O-imidazole equilibrium was extensively studied pointing to a 1:4 stoichiometry. The CuSALAD. B2 adducts exhibited certain catalytic properties that mimic those of catalase enzymes. The different imidazoles were buffered to acidic, neutral and basic pH media in order to investigate the pH effects of this reaction. Two charge transfer (CT) bands were observed near 420 and 450 nm upon addition of hydrogen peroxide to CuSALADB2 solutions, and were associated with two proposed intermediates (CuBOOH and CuBOOCu). A mechanism consistent with these results has been developed. First order dependence of the rate on CuSALAD. B2 was observed in the presence of excess CuSALAD. B2 over hydrogen peroxide whereas second order dependence was observed with the latter in excess. The CuBOOCu intermediate was unstable in the presence of EDTA and a first order dependence of rate of formation of intermediate on both CuSALAD. B2, and hydrogen peroxide was observed.

Vanadium is one of the more abundant elements in the Earth’s crust and exhibits a wide range of oxidation states in its compounds making it potentially a more sustainable and more economical choice as a catalyst than the noble metals. A wide variety of reactions have been found to be catalysed by homogeneous, supported and heterogeneous vanadium complexes and the number of applications is growing fast. Bringing together the research on the catalytic uses of this element into one essential resource, including theoretical perspectives on proposed mechanisms for vanadium catalysis and an overview of its relevance in biological processes, this book is a useful reference for industrial and academic chemists alike.