The valorization of CO 2 via photo-or electrocatalytic reduction constitutes a promising approach toward the sustainable production of fuels or value-added chemicals using intermittent renewable energy sources. For this purpose, molecular catalysts are generally studied independently with respect to the photo-or the electrochemical application, although a unifying approach would be much more effective with respect to the mechanistic understanding and the catalyst optimization. In this context, we present a combined photo-and electrocatalytic study of three Mn diimine catalysts, which demonstrates the synergistic interplay between the two methods. The photochemical part of our study involves the development of a catalytic system containing a heteroleptic Cu photosensitizer and the sacrificial BIH reagent. The system shows exclusive selectivity for CO generation and renders turnover numbers which are among the highest reported thus far within the group of fully earth-abundant photocatalytic systems. The electrochemical part of our investigations complements the mechanistic understanding of the photochemical process and demonstrates that in the present case the sacrificial reagent, the photosensitizer, and the irradiation source can be replaced by the electrode and a weak Brønsted acid.

An electrochemical approach toward rearrangement of O-aryl thiocarbamates to the corresponding S-aryl thiocarbamates is presented. The protocol requires only catalytic amounts of electric charge and allows for operation at room temperature. The electrolysis can be carried out with the simplest equipment, i.e., under galvanostatic conditions in an undivided cell. Furthermore, it is demonstrated that when the electrolysis is performed in a microflow reactor, almost quantitative yields can be achieved without using supporting electrolyte.

Hypervalent iodine compounds constitute a popular class of reagents in organic chemistry. Regardless of whether they are generated in situ from an iodoarene precursor with a terminal oxidant or used in stoichiometric amounts, the resulting separation and waste issues are major challenges en route to sustainable and scalable processes. The electrochemical generation of iodine(III) compounds represents an attractive alternative, since electric current is used as traceless oxidant and unstable or hazardous species are conveniently generated in situ. In this context, we have explored the possibility for the use of iodoarene sulfonates and iodobenzoates as ex‐cell mediators for electrosynthesis in 1,1,1,3,3,3‐hexafluoroisopropanol. While 2‐, 3‐ and 4‐iodobenzoate salts proved to be impractical for various reasons, 2‐ and 4‐iodobenzenesulfonates salts can be selectively oxidized to the iodine(III) species and used for synthetic applications. The ionic tag on the mediator allows for electrolysis without supporting electrolyte additives and enables a straightforward recovery from the product mixture.

In a previous paper we have demonstrated that the easily-synthesized class of iron(0) cyclopentadienone complexes constitutes a promising catalyst platform for the electrochemical conversion of CO2 to CO and H2O. One of the unusual features of these catalysts is that catalysis proceeds efficiently in aprotic electrolytes in the absence of acidic additives. Herein we present a detailed study of the underlying catalytic mechanisms. Using a combination of FTIR spectroelectrochemistry, DFT calculations, and nonelectrochemical control experiments, we have identified a number of catalytic intermediates including the active species and the product of catalyst deactivation. On the basis of these insights, we have carried out digital simulations in order to decipher the voltammetric profiles of the iron(0) cyclopentadienones. Further control experiments revealed that the anodic oxidation of the electrolyte constitutes the terminal proton source for the formation of CO and H2O. Taken together, our results suggest a competition between two coexisting catalytic pathways, one of which proceeds via a hitherto unknown Fe–Fe dimer as an active species.

The facilitation of redox-neutral reactions by electrochemical injection of holes and electrons, also known as “electrochemical catalysis”, is a little explored approach that has the potential to expand the scope of electrosynthesis immensely. To systematically improve existing protocols and to pave the way toward new developments, a better understanding of the underlying principles is crucial. In this context, we have studied the Newman–Kwart rearrangement of O-arylthiocarbamates to the corresponding S-aryl derivatives, the key step in the synthesis of thiophenols from the corresponding phenols. This transformation is a particularly useful example because the conventional method requires temperatures up to 300 °C, whereas electrochemical catalysis facilitates the reaction at room temperature. A combined experimental–quantum chemical approach revealed several reaction channels and rendered an explanation for the relationship between the structure and reactivity. Furthermore, it is shown how rapid cyclic voltammetry measurements can serve as a tool to predict the feasibility for specific substrates. The study also revealed distinct parallels to photoredox-catalyzed reactions, in which back-electron transfer and chain propagation are competing pathways.