N-Heterocyclic carbenes (NHCs) are nowadays ubiquitous in organometallic chemistry and catalysis. A simple synthetic route to these is presented.

Two new Zn(II) complexes with tridentate hydrazone-based ligands (condensation products of 2-acetylthiazole) were synthesized and characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy and single crystal X-ray diffraction methods. The complexes 1, 2 and recently synthesized [ZnL³(NCS)₂] (L³ = (E)-N,N,N-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium) complex 3 were tested as potential catalysts for the ketone-amine-alkyne (KA²) coupling reaction. The gas-phase geometry optimization of newly synthesized and characterized Zn(II) complexes has been computed at the density functional theory (DFT)/B3LYP/6–31G level of theory, while the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO and LUMO) energies were calculated within the time-dependent density functional theory (TD-DFT) at B3LYP/6-31G and B3LYP/6-311G(d,p) levels of theory. From the energies of frontier molecular orbitals (HOMO–LUMO), the reactivity descriptors, such as chemical potential (μ), hardness (η), softness (S), electronegativity (χ) and electrophilicity index (ω) have been calculated. The energetic behavior of the investigated compounds (1 and 2) has been examined in gas phase and solvent media using the polarizable continuum model. For comparison reasons, the same calculations have been performed for recently synthesized [ZnL³(NCS)₂] complex 3. DFT results show that compound 1 has the smaller frontier orbital gap so, it is more polarizable and is associated with a higher chemical reactivity, low kinetic stability and is termed as soft molecule.

Secondary ligand–metal interactions are decisive in many catalytic transformations. While arene–gold interactions have repeatedly been reported as critical structural feature in many high‐performance gold catalysts, we herein report that these interactions can also be replaced by Au⋅⋅⋅H−C hydrogen bonds without suffering any reduction in catalytic performance. Systematic experimental and computational studies on a series of ylide‐substituted phosphines featuring either a PPh₃ (^PhYPhos) or PCy₃ (^CyYPhos) moiety showed that the arene‐gold interaction in the aryl‐substituted compounds is efficiently compensated by the formation of Au⋅⋅⋅H−C hydrogen bonds. The strongest interaction is found with the C−H moiety next to the onium center, which due to the polarization results in remarkably strong interactions with the shortest Au⋅⋅⋅H−C hydrogen bonds reported to date. Calorimetric studies on the formation of the gold complexes further confirmed that the ^PhYPhos and ^CyYPhos ligands form similarly stable complexes. Consequently, both ligands showed the same catalytic performance in the hydroamination, hydrophenoxylation and hydrocarboxylation of alkynes, thus demonstrating that Au⋅⋅⋅H−C hydrogen bonds are equally suited for the generation of highly effective gold catalysts than gold‐arene interactions. The generality of this observation was confirmed by a comparative study between a biaryl phosphine ligand and its cyclohexyl‐substituted derivative, which again showed identical catalytic performance. These observations clearly support Au⋅⋅⋅H−C hydrogen bonds as fundamental secondary interactions in gold catalysts, thus further increasing the number of design elements that can be used for future catalyst construction.

The development of novel and operationally simple synthetic routes to carbene‐metal‐amido (CMA) complexes of copper, silver and gold relevant for photonic applications are reported. A mild base and sustainable solvents allow all reactions to be conducted in air and at room temperature, leading to high yields of the targeted compounds even on multigram scales. The effect of various mild bases on the N−H metallation was studied in silico and experimentally, while a mechanochemical, solvent‐free synthetic approach was also developed. Our photophysical studies on [M(NHC)(Cbz)] (Cbz=carbazolyl) indicate that the occurrence of fluorescent or phosphorescent states is determined primarily by the metal, providing control over the excited state properties. Consequently, we demonstrate the potential of the new CMAs beyond luminescence applications by employing a selected CMA as a photocatalyst. The exemplified synthetic ease is expected to accelerate the applications of CMAs in photocatalysis and materials chemistry.