published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

Neste trabalho foram estudadas as formas de coordenação de piridinonas, ditiocarbazatos e N-(N\'\',N\'\'-dialquilaminotiocarbonil)-N\'-(2-hidroxifenil)benzoamidinas aos centros metálicos Re (V) e Tc (V). Neste sentido, os complexos triclorobis(trifenilfosfina)oxorrênio(V), [ReOCl3(PPh3)2]57, tribromobis(trifenilfosfina)oxorrênio(V), [ReOBr3(PPh3)2]57, e tetraclorooxorenato(V) de tetrabutilamônio, (NBu4)[ReOCl4]58, foram sintetizados e utilizados como precursores. O precursor tetraclorooxotecnetato(V) de tetrabutilamônio, (NBu4)[TcOCl4], foi sintetizado e disponibilizado pelo grupo de Prof. Dr. Ulrich Abram, da Universidade Livre de Berlin, durante o período de trabalho realizado na Alemanha. <br /> Foram utilizadas as seguintes técnicas para a caracterização dos complexos sintetizados: espectroscopia de absorção na região do infravermelho, análise elementar (C, H, N e S), espectroscopia de ressonância magnética nuclear (31P, 1H e no caso de um dos complexos, também 13C), espectrometria de massas (MS-ESI) e determinação de estruturas cristalinas e moleculares, quando possível, por difração de raios X em monocristal. Por se tratar de um elemento radioativo, a avaliação do percentual de tecnécio em seus complexos foi determinada por meio da técnica de cintilação líquida. <br /> Deste o início deste trabalho foram sintetizados e caracterizados por diversas técnicas 14 novos complexos de rênio e 1 de tecnécio, todos inéditos. Seis ditiocarbazatos, sendo 5 inéditos, também foram sintetizados e caracterizados. / This work evaluated the coordination mode of pyridinones, dithiocarbazates and N-(N\'\',N\'\'-Diethylaminothiocarbonyl)-N\'-(2-hydroxyphenyl)benzamidine, to the metal centers Re (V) and Tc (V). For this purpose, the compounds trichlorobis(triphenylphosphine)oxorhenium(V), [ReOCl3(PPh3)2]43, tribromobis(triphenylphosphine)oxorhenium(V), [ReOBr3(PPh3)2]43, and tetra-n-butyl)ammonium tetrachlorooxorhenate(V), (NBu4)[ReOCl4]44, were synthesized and used as starting materials. The precursor tetra-n-butylammonium tetrachlorooxotechnetate(V), (NBu4)[TcOCl4] was synthesized and released by the Prof. Dr. Ulrich Abram\'s group, at the Freie Universität Berlin, during my research time in Germany. <br /> The complexes were characterized by infrared absorption spectroscopy, elemental analyses (CHNS), mass spectrometry with electrospray ionization (MSESI), nuclear magnetic resonance spectroscopy (31P, 1H and, in one case, also 13C) and had their crystalline and molecular structures, when possible, properties determined by X-ray diffraction on single crystals. Due to its radioactive element, the 99Tc values were determined by standard liquid scintillation counting. <br /> Since the beginning of this work were synthesized and characterized by various techniques 14 new rhenium and 1 technetium complexes, all of then unknown in the literature. All the complexes presented here were obtained in good or excellent yields. Six new dithiocarbazates were obtained and characterized, of which 5 are unknown.

Neste trabalho foram estudadas as formas de coordenação de piridinonas, ditiocarbazatos e N-(N\'\',N\'\'-dialquilaminotiocarbonil)-N\'-(2-hidroxifenil)benzoamidinas aos centros metálicos Re (V) e Tc (V). Neste sentido, os complexos triclorobis(trifenilfosfina)oxorrênio(V), [ReOCl3(PPh3)2]57, tribromobis(trifenilfosfina)oxorrênio(V), [ReOBr3(PPh3)2]57, e tetraclorooxorenato(V) de tetrabutilamônio, (NBu4)[ReOCl4]58, foram sintetizados e utilizados como precursores. O precursor tetraclorooxotecnetato(V) de tetrabutilamônio, (NBu4)[TcOCl4], foi sintetizado e disponibilizado pelo grupo de Prof. Dr. Ulrich Abram, da Universidade Livre de Berlin, durante o período de trabalho realizado na Alemanha. <br /> Foram utilizadas as seguintes técnicas para a caracterização dos complexos sintetizados: espectroscopia de absorção na região do infravermelho, análise elementar (C, H, N e S), espectroscopia de ressonância magnética nuclear (31P, 1H e no caso de um dos complexos, também 13C), espectrometria de massas (MS-ESI) e determinação de estruturas cristalinas e moleculares, quando possível, por difração de raios X em monocristal. Por se tratar de um elemento radioativo, a avaliação do percentual de tecnécio em seus complexos foi determinada por meio da técnica de cintilação líquida. <br /> Deste o início deste trabalho foram sintetizados e caracterizados por diversas técnicas 14 novos complexos de rênio e 1 de tecnécio, todos inéditos. Seis ditiocarbazatos, sendo 5 inéditos, também foram sintetizados e caracterizados. / This work evaluated the coordination mode of pyridinones, dithiocarbazates and N-(N\'\',N\'\'-Diethylaminothiocarbonyl)-N\'-(2-hydroxyphenyl)benzamidine, to the metal centers Re (V) and Tc (V). For this purpose, the compounds trichlorobis(triphenylphosphine)oxorhenium(V), [ReOCl3(PPh3)2]43, tribromobis(triphenylphosphine)oxorhenium(V), [ReOBr3(PPh3)2]43, and tetra-n-butyl)ammonium tetrachlorooxorhenate(V), (NBu4)[ReOCl4]44, were synthesized and used as starting materials. The precursor tetra-n-butylammonium tetrachlorooxotechnetate(V), (NBu4)[TcOCl4] was synthesized and released by the Prof. Dr. Ulrich Abram\'s group, at the Freie Universität Berlin, during my research time in Germany. <br /> The complexes were characterized by infrared absorption spectroscopy, elemental analyses (CHNS), mass spectrometry with electrospray ionization (MSESI), nuclear magnetic resonance spectroscopy (31P, 1H and, in one case, also 13C) and had their crystalline and molecular structures, when possible, properties determined by X-ray diffraction on single crystals. Due to its radioactive element, the 99Tc values were determined by standard liquid scintillation counting. <br /> Since the beginning of this work were synthesized and characterized by various techniques 14 new rhenium and 1 technetium complexes, all of then unknown in the literature. All the complexes presented here were obtained in good or excellent yields. Six new dithiocarbazates were obtained and characterized, of which 5 are unknown.

This thesis reports the studies on the reaction of 1-azabutadienes with PhCH2Re(CO)5 to prepare the cyclometallated azabutadiene tetracarbonyl compounds. Three 1-azabutadienes with different reactivity on the N and C-1 carbons were prepared and their reactions with PhCH2Re(CO)5 were investigated. All the reactions gave a mixture of the cyclorheniated azabutadienes and the isomers of the substituted derivatives formed by substitution by a second azabutadiene. The substituted derivatives as the mixture were always the main products of the reactions and were obtained in good-to-excellent yield even under modified conditions intended to optimise the yield of the cyclorheniated azabutadienes. The yield could not be improved beyond 30 %. Isomerisation of the azabutadiene about the N=C bond provided very rare cis-azabutadiene metal complexes. NMR studies on the mixture of the two isomers and suggested that the product ratio depended on the molar ratio of PhCH2Re(CO)5 in the reaction mixtures. The reactions gave the Re analogues of the products obtained in the corresponding Mn reactions. All the compounds were characterised spectroscopically as well as by microanalysis and examples of all three types were structurally determined by X-ray crystallography. The reactions of the substituted derivative as the mixture of the two isomers with unsaturated molecules including phenyl acetylene, p-methoxyphenyl isocyanide, and phenyl isocyanate and methyl acrylate were investigated.

The transition metal complexes cyclopentadienylrhenium tricarbonyl [CpRe(CO)3, Cp = cyclopentadienyl] and (isopropylcyclopentadienyl)rhenium tricarbonyl [(i-PrCp)Re(CO)3, i-Pr = isopropyl] were photolysed in alkanes at low temperature and the resulting alkane complexes, of the general formula Cp'Re(CO)2(alkane) (Cp' = Cp or (i-PrCp)), were studied using NMR spectroscopy. Characteristic proton chemical shifts (δ) and couplings (3JHH) were observed for alkane complexes of several linear, branched and cyclic alkanes of up to eight carbons. Alkanes with chemically distinct methyl (CH3) and/or methylene (CH2) units were observed alternatively binding through each unit to rhenium. No bound methine unit was observed. Large C-H coupling constants (1JCH) were observed for protons of several bound CH3 and CH2 units, indicating the bound C-H is intact. These species are, thus, alkane sigma (σ) complexes, wherein the alkane has an agostic (M-H-C, 3 centre 2 electron) interaction with the rhenium centre. The CH3 binding mode of (i-PrCp)Re(CO)2(1-pentane) was elucidated; sequential deuteration in the bound CH3 revealed an equilibrium isotope effect (EIE) in the remaining proton/s, confirming that only one C-H has an agostic interaction with rhenium at any instant . NMR parameters δ(1H) (-8.22), δ(13C) ( 42.4) and 1JCH (85 Hz) for the complexed C-H reveal it is unequivocally intact and yet strongly interacting with the rhenium centre, hallmarks for the agostic interaction. Intramolecular exchange was identified between pentane complex isomers Cp'Re(CO)2(1-pentane), Cp'Re(CO)2(2-pentane) and Cp'Re(CO)2(3-pentane). Equilibrium constants were determined, revealing a preference for CH2 binding over CH3. The inequivalent hydrogens found in methylene groups of cyclohexane at low temperature permitted simultaneous observation of axial and equatorial C-H protons of a bound CH2 in CpRe(CO)2(cyclohexane); an EIE, upon deuteration, indicated rapid exchange between complexed C-H bonds in the bound CH2 unit. The rhenium centre was found to prefer complexation of the axial C-H bond, over the equatorial, with K ~2.9. Intermolecular exchange of alkane ligands with free solvent was directly observed, in the competitive complexation of the [CpRe(CO)2] fragment to different alkanes in binary mixtures. The preference cyclohexane > cyclopentane > pentane > isobutane was established and equilibrium constants determined. The kinetics were followed by NMR and modelled, revealing rate constants; decay rates were also determined.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

In situ reduction of hydrido-tris-(3,5-dimethylpyrazolyl)borato(trioxo) rhenium(V) with triphenylphosphine or triethylphosphite leads to a reactive rhenium(V) species that catalytically deoxygenates epoxides at 75-105��C. The reaction is stereospecific, except for trans- and cis-butene oxide which formed minor amounts of the opposite isomer. A variety of different functional groups were tolerated and even epoxides that reacted slowly could be pushed to greater than 95% conversion given extended time and/or higher temperature. The absence of clustering processes shows how the choice of ligand can have a major influence on the design of the catalytic cycle. The rhenium(V) species formed from reduction of Tp'ReO��� was identified as Tp'Re(O)(OH)���. Tp'Re(O)(OH)��� reacted with ethanol and HCl to form ethoxide and hydroxo chloride complexes, respectively. In addition, Tp'Re(O)(OH)��� was an excellent catalytic and stoichiometric reagent for the deoxygenation of epoxides and sulfoxides. Loss of water from Tp'Re(O)(OH)��� to form the catalytically active species Tp'Re02 was shown to be a necessary preequilibrium process. The kinetic behavior of the catalytic system is complex. First-order behavior in [Re][subscript T], zero-order dependence in [PPh���] and saturation behavior for epoxide were observed. The reversible formation of a coordinated epoxide complex was proposed to explain the saturation behavior. The epoxide complex was shown experimentally and computationally to engage in two separate reactions: ring expansion to form a syn-diolate complex, and direct fragmentation to alkene and trioxide. A steady-state concentration of diolate is eventually reached explaining a "burst" of alkene production prior to generation of a pseudo-zero-order catalytic system. The diolate formed is the syn-isomer, which is the kinetically formed product. Direct epoxide fragmentation is the primary source of alkene. This process was determined to be four times faster than ring expansion for cis-stilbene oxide. The synthesis and characterization of a tethered-epoxide Cp* rhenium trioxide complex has been achieved. Reduction of this complex leads to an unsaturated rhenium(V) species that is immediately complexed by the tethered epoxide. Experimental data and molecular mechanics modeling support intramolecular coordination of the epoxide to the rhenium center. These results confirm that the coordinate epoxide is a viable intermediate in rhenium-catalyzed epoxide deoxygenations. / Graduation date: 2003

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, June 1999. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 153-156). Also available on the Internet.