A redox-switchable catalyst with an ‘unplugged’ redox tag

Abstract

Two bis-(propyl-imidazolium)-napthalenediimide (NDI) salts were prepared and used as N-Heterocyclic carbene (NHC) precursors for the preparation of dimetallic complexes of rhodium and iridium. Infrared spectroelectrochemical studies indicate that the metals...

Tuning the Catalytic Activity of a Pincer Complex of Rhodium(I) by Supramolecular and Redox Stimuli

“…The reaction was carried out in CD 3 CN at 80 °C, and the evolution of the process was monitored by 1 H NMR spectroscopy. As can be observed from the time‐dependent reaction profile shown in Figure 6a, the reaction exhibits a zeroth order dependence on the substrate, in accordance with previous studies, [12a,c,18] and under these reaction conditions the reaction rate is 1.18±0.04×10 −5 Ms −1 . Then the reaction was repeated under the same conditions, but with the addition of coronene or TBAF.…”

“…In order to address this point, we decided to study the catalytic activity of 2 in the cycloisomerization of alkynoic acids as a model catalytic reaction. We find this reaction suitable for the study, because it is an easy NMR‐monitorable reaction, and because in previous studies we found this reaction is very sensitive to changes in the electron‐donating properties of the ligands and, therefore, particularly useful for carrying out studies on redox‐switchable [12a,c] and supramolecularly modified [8] catalysts. We first studied the cycloisomerization of 4‐pentynoic acid in the presence of 1 mol % of complex 2 .…”

Supramolecular Control of the Oxidative Addition as a Way To Improve the Catalytic Efficiency of Pincer‐Rhodium (I) Complexes

“…The resulting reaction profiles are shown in Figure 4. As can be observed from the plots, the reactions follow a zeroth order dependence on the substrate, in agreement with previous studies [8c,d,23] . This zeroth order dependence of the reaction rate on the substrate concentration means that the resting state the substrate is already coordinated to the catalyst through the alkyne.…”

“…As can be observed in the plots shown in Figure 4, the addition of coronene produces a significant improvement in the catalytic activity, which is manifested by a 2.7‐fold increase of the reaction rate. It is also important to point out that this enhancement on the activity of the catalyst for this specific reaction is similar to that obtained using rhodium complexes with redox‐switchable ligands, [8c,d] thus indicating that the supramolecular control of the process can compete in magnitude with the control provided by redox‐switchable catalysts. Again, when we performed the reaction in the presence of pyrene, instead of coronene, no improvement in the reaction rate was observed, as a consequence of the negligible interaction between pyrene and complex 1 (Figure S26).…”

Dehydrative Coupling of Alcohols by Iridium(III) Complexes with N-Heterocyclic-Pyridine Chelating Ligands Decorated with Naphthalene-Diimide

“…We recently became interested in the use of NDI and PDI functionalities for the preparation of NHC-based redox-switchable catalysts. The presence of the NDI or PDI moieties appended to the NHC ligands allowed toggling the properties of the metals between three electronic levels, and this was used for exploring the redox-switchable properties of the catalysts in the cycloisomerization of alkynoic acids, the hydroamination of alkynes, and the [3+2] cycloaddition of diphenylcyclopropenone and acetylenes . In the incorporation of the NDI moieties into the NHC ligand, we used two strategies, which included the fusion of the NHC ligand at the core positions of the NDI moiety ,, or the functionalization of the NDI at the imide positions .…”