3 research outputs found

    Mechanistic Study on the Addition of CO<sub>2</sub> to Epoxides Catalyzed by Ammonium and Phosphonium Salts: A Combined Spectroscopic and Kinetic Approach

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    Herein we report the evaluation of the frequently employed tetrabutyl ammonium and phosphonium halides as well as their bifunctional analogs as catalysts in cyclic carbonate synthesis under benchmarked conditions. The kinetic data of all catalysts were evaluated and the rate constants determined. Moreover, a systematic infrared spectroscopic study of the interactions between cation and anion of the catalysts as well as the interactions between the catalysts and the substrate were conducted. These experimental results were additionally supported by DFT calculations. The observed trends in the interaction between the onium cation and the anion are correlated to their catalytic activity. Moreover, these investigations revealed the mode of the substrate activation for the monofunctional and the bifunctional catalysts. Furthermore, the kinetic studies and in situ infrared experiments revealed a product inhibition of the bifunctional catalysts via the unexpected formation of catalyst–carbonate adducts. The interaction between the catalysts and the product was further studied by infrared spectroscopy. Finally, the rate and the equilibrium constants for the binfunctional catalysts were determined by a Michaelis–Menten model considering a reversible product inhibition

    From Internal Olefins to Linear Amines: Ruthenium-Catalyzed Domino Water–Gas Shift/Hydroamino­methylation Sequence

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    A selective ruthenium-catalyzed water–gas shift/hydroformylation of internal olefins and olefin mixtures is reported. This novel domino reaction takes place through a catalytic water–gas shift reaction, subsequent olefin isomerization, followed by hydroformylation and reductive amination. Key to the success for the efficient one-pot process is the use of a specific 2-phosphino-substituted imidazole ligand and triruthenium dodecacarbonyl as precatalyst. Industrially important internal olefins react with various amines to give the corresponding tertiary amines generally in good yield and selectivity. This reaction sequence constitutes an economically attractive and environmentally favorable process for the synthesis of linear amines

    Investigation into the Equilibrium of Iridium Catalysts for the Hydroformylation of Olefins by Combining In Situ High-Pressure FTIR and NMR Spectroscopy

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    A detailed quantitative study of phosphine-modified hydrido iridium complexes relevant for the hydroformylation reaction has been performed using HP-FTIR and HP-NMR spectroscopy. The equilibrium composition under typical reaction conditions has been characterized. Investigation of the temperature dependency allowed even for a distinction between both configurational isomers of [HIr­(CO)<sub>2</sub>(PPh<sub>3</sub>)<sub>2</sub>]. The trihydride complex [H<sub>3</sub>Ir­(CO)­(PPh<sub>3</sub>)<sub>2</sub>] is part of the investigated equilibrium depending on the ratio of <i>p</i>(H<sub>2</sub>)/<i>p</i>(CO). Single rate constants for the sequence of corresponding equilibrium reactions have been estimated from stopped-flow experiments and conventional measurements, monitoring the concentrations after changing reactant concentrations
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