Date of Award:

5-1996

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Chemistry and Biochemistry

Advisor/Chair:

John L. Hubbard

Abstract

This work is concentrated on the thermodynamic and kinetic aspects of water, alcohols, alkyl halides, ethers, and lactones bound and activated by the electrophilic [Cp'Ru(N0)] +2 and [Cp’Ru (NO)(CH3)] + centers (Cp' = cyclopentadienyl group). Counterions in these systems include OSO2CF3- (OTf-) and [(3, 5-(CF3)2C6H3)4B]- ([BAr4']-). The displacement of OTf- in Cp'Ru(N0) (0Tf)2 by H20 in dichloromethane is exothermic but entropically unfavorable due to the required reorganization of the solvent cage around released triflate ions. Thermodynamic parameters are also determined for OTf displacement by chloride and tetrahydrofuran (THF) using the 19F nuclear magnetic resonance (NMR) spectroscopy. The conversion of the [Cp’Ru (NO)(OH2)2] +2 to [Cp’Ru (NO)(μ-OH)} 2 +2 in aqueous solutions is characterized thermodynamically and kinetically by potentiometric and NMR methods.

The results of the study of rhodium triflato complex trans- [Rh (CO)(PPh3)2(OTf)] show that OTf coordinates to the metal center in wet dichloromethane solutions, but the compound crystallizes as a water-coordinated triflate salt trans- [Rh (CO)(PPh3)2(OH2)] [OTf]. Thermodynamic parameters for alcohol (methanol, ethanol, isopropanol) binding to the Cp*Ru(N0) (0Tf)2 are determined from the 19F NMR spectroscopic data. The kinetics of the oxidation of alcohols to aldehydes or ketones via Ru (II) >>> Ru (0) redox process is studied by NMR methods. The results of the study support {3-hydrogen elimination mechanism, comprising one of the very few mechanistic investigations on reactions of this kind. Alkyl iodides are found to bind to the [Cp*Ru (NO)(CH3)] + fragment via displacement of a THF ligand in the presence of a BAr4 •-counterion, forming alkyl halide complexes that convert to [Cp’Ru (NO)(μ-I)]2+2. The mixed ruthenium-chromium complex [CpCr (NO)2(μ-I) (Ru (Cp’) (NOW is characterized as primarily a [Ru-I >> Cr] system as opposed to a [Ru << I-Cr] model. The complex [Cp*Ru (NO)(CH3) (THF)] is found to catalyze aerobic oxidation of THF to -y-butyrolactone. The new -y-butyrolactone ruthenium complex is isolated and characterized by X-ray methods in the solid state. The mechanism of catalytic oxidation is studied by 18O-labeled infrared spectroscopic methods. Radical decomposition of the intermediate hydroperoxy-tetrahydrofuran gives 1, 6-diol-diformate [CH(O)-(CH2)6-CH(O)]. The radical mechanism for the catalytic oxidation of THF is proposed.

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Chemistry Commons

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