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Reaction intermediates in homogeneous gold catalysis
Shcherbachenko, Elena ; Roithová, Jana (advisor) ; Matoušová, Eliška (referee)
The presented master thesis is devoted to the investigation of reaction intermediates in homogeneous gold catalysis. Electrospray ionization mass spectrometry (ESI-MS) was used as the primary research technique in this study. Delayed reactant labeling was used as the main method. I have focused mainly on the hydration of 1-phenyl-1-propyne catalyzed by the gold complex [Au(IPr)(MeCN)]BF4 (IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2- ylidene). I have detected two main intermediates containing one or two gold atoms, respectively (monoaurated and diaurated intermediate). I have obtained rate constants for the degradation of the reaction intermediates and their half-lives. I have derived kinetic isotope effects for the formation and the decomposition of the detected intermediates. I have shown that the kinetics of the degradation of both intermediates is identical, therefore I conclude that hydration of alkynes catalyzed by gold complex [Au(IPr)(MeCN)]BF4 proceeds most probably via neutral monoaurated intermediates. These neutral intermediates are detected by ESI-MS as protonated (monoaurated intermediate) or tagged by a second gold cation (diaurated intermediate). Key words: gold catalysis, reaction intermediates, electrospray ionization, mass spectrometry.
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Characterization of organogold compounds
Shcherbachenko, Elena ; Roithová, Jana (advisor) ; Míšek, Jiří (referee)
Geminally diaurated complexes are important intermediates involved in some of the gold catalyzed reactions and therefore they have become a subject of the current research. The aim of this thesis was to assess the influence of electronic structure of an aryl ligand on the stability of gold complexes with three-center-two-electron interaction Au2C. A series of geminally diaurated complexes was obtained by a reaction of gold complex [(IPr)Au(NCMe)]BF4 (IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2-ylidene) with arylboronic acids ArB(OH)2 bearing different substituents at the aryl group (Ar = para- O2NC6H4, para-NCC6H4, para-ClC6H4, C6H5, para-H3CC6H4, para-H3COC6H4, meta- O2NC6H4, meta-NCC6H4, meta-H3CC6H4, ortho-O2NC6H4, ortho-NCC6H4, ortho-H3CC6H4). Mass spectrometry (MS) was used as the main experimental method in this study. Appearance energies (AE) for the fragmentation of geminally diaurated complexes were estimated by the methods MS/MS. The obtained energies were plotted against the corresponding Hammett σ-constants to assess the correlation between the electronic structure of a given aryl ligand and the stability of the Au2C bond. It was found that structures of gold complexes derived from the cyanophenylboronic acids do not correspond to the geminally diaurated complexes but to the...
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Research of gold catalyzed reactions
Jašíková, Lucie ; Roithová, Jana (advisor) ; Polášek, Miroslav (referee) ; Starý, Ivo (referee)
The main focus of the current dissertation thesis is research of gold catalyzed reactions. I was using mass spectrometry as the primary research technique. I complemented the results with infrared multiphoton dissociation spectroscopy, nuclear magnetic resonance spectroscopy and quantum chemical calculations. I have investigated the interaction of the gold(I) cation with unsaturated hydrocarbons in the first part of my thesis. Secondly, I have studied gold(I) or silver(I) affinity to gold acetylides. In the last part, I have investigated the reaction mechanism of a gold mediated addition of methanol to alkynes. I found out that the gold(I) cation interacts stronger with gold acetylides than with nonactivated triple CC bonds. I showed that the complexes containing two gold atoms represent the key intermediates in the mechanism of addition of methanol to alkynes and that the ligand on the gold catalyst plays a fundamental role in the determination of the mechanism. Powered by TCPDF (www.tcpdf.org)
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Reaction intermediates in homogeneous gold catalysis
Shcherbachenko, Elena ; Roithová, Jana (advisor) ; Matoušová, Eliška (referee)
The presented master thesis is devoted to the investigation of reaction intermediates in homogeneous gold catalysis. Electrospray ionization mass spectrometry (ESI-MS) was used as the primary research technique in this study. Delayed reactant labeling was used as the main method. I have focused mainly on the hydration of 1-phenyl-1-propyne catalyzed by the gold complex [Au(IPr)(MeCN)]BF4 (IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2- ylidene). I have detected two main intermediates containing one or two gold atoms, respectively (monoaurated and diaurated intermediate). I have obtained rate constants for the degradation of the reaction intermediates and their half-lives. I have derived kinetic isotope effects for the formation and the decomposition of the detected intermediates. I have shown that the kinetics of the degradation of both intermediates is identical, therefore I conclude that hydration of alkynes catalyzed by gold complex [Au(IPr)(MeCN)]BF4 proceeds most probably via neutral monoaurated intermediates. These neutral intermediates are detected by ESI-MS as protonated (monoaurated intermediate) or tagged by a second gold cation (diaurated intermediate). Key words: gold catalysis, reaction intermediates, electrospray ionization, mass spectrometry.
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Characterization of organogold compounds
Shcherbachenko, Elena ; Roithová, Jana (advisor) ; Míšek, Jiří (referee)
Geminally diaurated complexes are important intermediates involved in some of the gold catalyzed reactions and therefore they have become a subject of the current research. The aim of this thesis was to assess the influence of electronic structure of an aryl ligand on the stability of gold complexes with three-center-two-electron interaction Au2C. A series of geminally diaurated complexes was obtained by a reaction of gold complex [(IPr)Au(NCMe)]BF4 (IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2-ylidene) with arylboronic acids ArB(OH)2 bearing different substituents at the aryl group (Ar = para- O2NC6H4, para-NCC6H4, para-ClC6H4, C6H5, para-H3CC6H4, para-H3COC6H4, meta- O2NC6H4, meta-NCC6H4, meta-H3CC6H4, ortho-O2NC6H4, ortho-NCC6H4, ortho-H3CC6H4). Mass spectrometry (MS) was used as the main experimental method in this study. Appearance energies (AE) for the fragmentation of geminally diaurated complexes were estimated by the methods MS/MS. The obtained energies were plotted against the corresponding Hammett σ-constants to assess the correlation between the electronic structure of a given aryl ligand and the stability of the Au2C bond. It was found that structures of gold complexes derived from the cyanophenylboronic acids do not correspond to the geminally diaurated complexes but to the...
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