Mechanisms of metal-catalyzed reactions: an electrospray ionization mass spectrometry approach

Mass spectrometry, ion spectroscopy, NMR and quantum-chemical calculations are commonly combined to study the structures, properties and reactivity of intermediates in metal- catalyzed reactions. However, our ability to identify the main species present in solution by electrospray ionization mass spectrometry (ESI-MS) and to confirm whether these species are indeed reactive intermediates involved in the study reactions remains limited. Thus, we developed a new method combining isotope labeling with kinetic data extraction for the identification and analysis of intermediates in reaction mixtures termed delayed reactant labeling (DRL). Accordingly, this thesis is divided into 5 Chapters. Chapter 1 gives an overview of ESI-MS as a tool for studying the mechanisms of metal-catalyzed reactions, focusing on gold chemistry. Chapter 2 describes the experimental (ESI-MS, ion spectroscopy and gas chromatography) and theoretical (DFT) methods used in this thesis and the corresponding instrumentation. Chapter 3 details the development of the delayed reactant labeling (DRL) as a technique for studying reaction kinetics by mass spectrometry and examples how it was used to investigate problems in the following chapter. Chapter 4, shows that a Au(I) complex can act as a strong base in a solution containing water..

Mechanismy reakcí katalyzových kovy: Přístup pomocí hmotnostní spektrometrie s elektrosprejovou ionizací

Hmotnostní spektrometrie, iontová spektroskopie, NMR spektroskopie a kvantově- chemické výpočty se běžně kombinují za účelem studia struktur, vlastností a reaktivity meziproduktů v reakcích katalyzovaných sloučeninami kovů. Nicméně naše schopnost identifikovat reaktivní komplexy v roztoku pomocí hmotnostní spektrometrie s elektroprejovou ionizací (ESI-MS) a potvrdit, že tyto komplexy jsou skutečně reaktivními meziprodukty, zůstává omezená. Proto jsme vyvinuli novou metodu, zpožděné značení reaktantů (DRL), založenou na izotopovém značení reaktantů s prodlevou, což umožňuje získání kinetických dat z roztoku spojených s komplexy detekovanými pomocí ESI-MS. Tato práce je rozdělena do 5 kapitol. Kapitola 1 podává přehled ESI-MS jako nástroje pro studium mechanismů reakcí katalyzovaných komplexy kovů se zaměřením na chemii zlata. Kapitola 2 popisuje experimentální (ESI-MS, iontovou spektroskopii a plynovou chromatografii) a teoretické (DFT) metody použité v této práci a odpovídající instrumentaci. Kapitola 3 podrobně popisuje vývoj metody zpožděné značení reaktantů pro studium reakční kinetiky pomocí hmotnostní spektrometrie a příklady toho, jak byla použita při zkoumání problémů v následujících kapitolách. Kapitola 4 ukazuje, že komplex Au(I) může působit jako silná báze v roztoku obsahujícím vodu díky...Mass spectrometry, ion spectroscopy, NMR and quantum-chemical calculations are commonly combined to study the structures, properties and reactivity of intermediates in metal- catalyzed reactions. However, our ability to identify the main species present in solution by electrospray ionization mass spectrometry (ESI-MS) and to confirm whether these species are indeed reactive intermediates involved in the study reactions remains limited. Thus, we developed a new method combining isotope labeling with kinetic data extraction for the identification and analysis of intermediates in reaction mixtures termed delayed reactant labeling (DRL). Accordingly, this thesis is divided into 5 Chapters. Chapter 1 gives an overview of ESI-MS as a tool for studying the mechanisms of metal-catalyzed reactions, focusing on gold chemistry. Chapter 2 describes the experimental (ESI-MS, ion spectroscopy and gas chromatography) and theoretical (DFT) methods used in this thesis and the corresponding instrumentation. Chapter 3 details the development of the delayed reactant labeling (DRL) as a technique for studying reaction kinetics by mass spectrometry and examples how it was used to investigate problems in the following chapter. Chapter 4, shows that a Au(I) complex can act as a strong base in a solution containing water...Katedra organické chemieDepartment of Organic ChemistryFaculty of SciencePřírodovědecká fakult

Why can a gold salt react as a base?

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Reaction Intermediates Kinetics in Solution Investigated by Electrospray Ionization Mass Spectrometry: Diaurated Complexes

A new method to investigate the reaction kinetics of intermediates in solution by electrospray ionization mass spectrometry is presented. The method, referred to as delayed reactant labeling, allows investigation of a reaction mixture containing isotopically labeled and unlabeled reactants with different reaction times. It is shown that we can extract rate constants for the degradation of reaction intermediates and investigate the effects of various reaction conditions on their half-life. This method directly addresses the problem of the relevance of detected gaseous ions toward the investigated reaction solution. It is demonstrated for geminally diaurated intermediates formed in the gold mediated addition of methanol to alkynes. Delayed reactant labeling allows us to directly link the kinetics of the diaurated intermediates with the overall reaction kinetics determined by NMR spectroscopy. It is shown that the kinetics of protodeauration of these intermediates mirrors the kinetics of the addition of methanol demonstrating they are directly involved in the catalytic cycle. Formation as well as decomposition of diaurated intermediates can be drastically slowed down by employing bulky ancillary ligands at the gold catalyst; the catalytic cycle then proceeds via monoaurated intermediates. The reaction is investigated for 1-phenylpropyne (Ph–CC–CH₃) using [AuCl­(PPh₃)]/AgSbF₆ and [AuCl­(IPr)]/AgSbF₆ as model catalysts. Delayed reactant labeling is achieved by using a combination of CH₃OH and CD₃OH or Ph–CC–CH₃ and Ph–CC–CD₃