Jarl Ivar van der Vlugt

This study explores the impact of (i) different installation modes of the molecular rhenium catalyst Re within the PCN‐777 metal–organic framework (MOF) and (ii) catalyst loading on the resulting catalytic performance and recyclability of the different hybrid materials in the photocatalytic reduction of CO ₂ to CO. Through systematic investigation, we demonstrate that a robust coordination linkage between a zirconium node of the framework and the catalyst, obtained via solvent‐assisted ligand incorporation (SALI), minimizes rhenium leaching. In contrast, physical entrapment and electrostatic anchoring methods result in significant rhenium leaching after installation. Additionally, we reveal how the installation mode influences the electronic properties of the catalyst, which allows us to tune the catalytic activity. Furthermore, based on these results, we determine the optimal loading and concentration of Re within the MOF matrix for photocatalytic CO ₂ reduction.

The utilization of iron-catalyzed intramolecular C(sp³)-H amination starting from organic aliphatic azides, which are easily available precursors, represents a particularly promising route to synthesize sought-after N-heterocyclic motifs. While significant advances in achiral iron catalysis have been made by the field in recent years, we introduce here a new, highly reactive chiral diamine-bisoxazoline iron(II) system for asymmetric C-H amination with primary azides. The presence of two distinctly different chiral components, i.e., an atropisomeric binaphthyl-diamine backbone and two stereochemically identical oxazoline units, leads to the formation of four stereoisomers, which revealed distinctly different reactivity for the two sets of diastereomers available. Kinetic experiments and detailed computation studies point to a stepwise radical mechanism after the initial rate-limiting azide activation via a 1,5-HAT process at the quintet spin surface. Ligand modification (substitution at the oxazoline ring) significantly enhanced the reactivity, chemoselectivity, and enantioselectivity, thus enabling the synthesis of pyrrolidines in high yield with good stereocontrol under mild, additive-free conditions and with N₂ as the sole byproduct.

Integration of a photocathode, CoCpCp* as redox-mediator and a heterogenized rhenium catalyst within PCN-777 provides a proof-of-concept DS-MOF-PEC system for light-driven CO ₂ reduction.

Here, we present the development and characterization of the novel PhenTAA macrocycle as well as a series of [Ni(R₂PhenTAA)]ⁿ complexes featuring two sites for ligand-centered redox-activity. These differ in the substituent R (R = H, Me, or Ph) and overall charge of the complex n (n = -2, -1, 0, +1, or +2). Electrochemical and spectroscopic techniques (CV, UV/vis-SEC, X-band EPR) reveal that all redox events of the [Ni(R₂PhenTAA)] complexes are ligand-based, with accessible ligand charges of -2, -1, 0, +1, and +2. The o-phenylenediamide (OPD) group functions as the electron donor, while the imine moieties act as electron acceptors. The flanking o-aminobenzaldimine groups delocalize spin density in both the oxidized and reduced ligand states. The reduced complexes have different stabilities depending on the substituent R. For R = H, dimerization occurs upon reduction, whereas for R = Me/Ph, the reduced imine groups are stabilized. This also gives electrochemical access to a [Ni(R₂PhenTAA)]^2- species. DFT and TD-DFT calculations corroborate these findings and further illustrate the unique donor-acceptor properties of the respective OPD and imine moieties. The novel [Ni(R₂PhenTAA)] complexes exhibit up to five different ligand-based oxidation states and are electrochemically stable in a range from -2.4 to +1.8 V for the Me/Ph complexes (vs Fc/Fc⁺).

A heteroleptic supramolecular square containing perylene-diimide moieties features photocatalytic activity for dehalogenation reactions, influenced by substrate binding.

In this paper, we report the synthesis of a unique silicon(I)-based metalla-disilirane and report on its reactivity toward TMS-azide and benzophenone. Metal complexes containing disilylenes ((bis)silylenes with a Si-Si bond) are known, but direct ligation of the Si(I) centers to transition metals always generated dinuclear species. To overcome this problem, we targeted the formation of a mononuclear iron(0)-silicon(I)-based disilylene complex via templated synthesis, starting with ligation of two Si(II) centers to iron(II), followed by a two-step reduction. The DFT structure of the resulting η²-disilylene-iron complex reveals metal-to-silicon π-back donation and a delocalized three-center-two-electron (3c-2e) aromatic system. The Si(I)-Si(I) bond displays unusual but well-defined reactivity. With TMS-azide, both the initial azide adduct and the follow-up four-membered nitrene complex could be isolated. Reaction with benzophenone led to selective 1,4-addition into the Si-Si bond. This work reveals that selective reactions of Si(I)-Si(I) bonds are made possible by metal ligation.

In this paper we report the synthesis of a unique silicon(I)-based metalla-disilirane and report on its reactivity towards TMS-azide and benzophenone. Metal complexes containing disilylenes ((bis)silylenes with a Si‒Si bond) are known, but direct ligation of the Si(I) centers to transition metals has thus far always resulted in formation of multinuclear species. To overcome this problem, we targeted the formation of a mononuclear iron(0)-silicon(I)-based disilylene complex via templated synthesis, starting with ligation of a Si(II)- source to iron(II), followed by a two-step reduction. The DFT structure of the resulting η2-disilylene-iron complex reveals metal-to-silicon -back donation and a delocalized three-center-two-electron (3c‒2e) aromatic system. The Si(I)‒Si(I) bond displays unusual but well-defined reactivity. With TMS-azide, both the azide adduct and the four-membered nitrene complex could be isolated. Reaction with benzophenone led to selective 1,4-addition into the SiSi bond. This work reveals that selective reactions of Si(I)‒Si(I) bonds are made possible by metal ligation.

The cobalt species PPh₄[Co^III(TAML^red)] is a competent and stable catalyst for the sulfimidation of (aryl)(alkyl)‐substituted sulfides with iminoiodinanes, reaching turnover numbers up to 900 and turnover frequencies of 640 min⁻¹ under mild and aerobic conditions. The sulfimidation proceeds in a highly chemoselective manner, even in the presence of alkenes or weak C−H bonds, as supported by inter‐ and intramolecular competition experiments. Functionalization of the sulfide substituent with various electron‐donating and electron‐withdrawing arenes and several alkyl, benzyl and vinyl fragments is tolerated, with up to quantitative product yields. Sulfimidation of phenyl allyl sulfide led to [2,3]‐sigmatropic rearrangement of the initially formed sulfimide species to afford the corresponding N‐allyl‐S‐phenyl‐thiohydroxylamines as attractive products. Mechanistic studies suggest that the actual nitrene transfer to the sulfide proceeds via (previously characterized) electrophilic nitrene radical intermediates that afford the sulfimide products via electronically asynchronous transition states, in which SET from the sulfide to the nitrene radical complex precedes N−S bond formation in a single concerted process.