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
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/HydroaminoÂmethylation Sequence
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
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 [HIrÂ(CO)<sub>2</sub>(PPh<sub>3</sub>)<sub>2</sub>]. The trihydride complex [H<sub>3</sub>IrÂ(CO)Â(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