Synthesis and comparative study of (NHC)PdClPy and (NHC)Ni(Cp)Cl complexes: investigation of the electronic properties of NHC ligands and complex characteristics.

The electron-donating and electron-accepting properties of N-heterocyclic carbene (NHC) ligands play a pivotal role in governing their interactions with transition metals, thereby influencing the selectivity and reactivity in catalytic processes. Herein, we report the synthesis of Pd/NHC and Ni/NHC complexes, wherein the electronic parameters of the NHC ligands were systematically varied. By performing a series of controlled structure modifications, we elucidated the influence of the σ-donor and π-acceptor properties of NHC ligands on interactions with the transition metals Pd and Ni and, consequently, the catalytic behavior of Pd and Ni complexes.

Revealing the Mechanism of Combining Best Properties of Homogeneous and Heterogeneous Catalysis in Hybrid Pd/NHC Systems.

The formation of transient hybrid nanoscale metal species from homogeneous molecular precatalysts has been demonstrated by in situ NMR studies of catalytic reactions involving transition metals with N-heterocyclic carbene ligands (M/NHC). These hybrid structures provide benefits of both molecular complexes and nanoparticles, enhancing the activity, selectivity, flexibility, and regulation of active species. However, they are challenging to identify experimentally due to the unsuitability of standard methods used for homogeneous or heterogeneous catalysis.

An Unusual Microdomain Factor Controls Interaction of Organic Halides with the Palladium Phase and Influences Catalytic Activity in the Mizoroki-Heck Reaction.

In this work, using a combination of scanning and transmission electron microscopy (SEM and TEM), the transformations of palladium-containing species in imidazolium ionic liquids in reaction mixtures of the Mizoroki-Heck reaction and in related organic media are studied to understand a challenging question of the relative reactivity of organic halides as key substrates in modern catalytic technologies. The microscopy technique detects the formation of a stable nanosized palladium phase under the action of an aryl (Ar) halide capable of forming microcompartments in an ionic liquid. For the first time, the correlation between the reactivity of the aryl halide and the microdomain structure is observed: Ar-I (well-developed microdomains) > Ar-Br (microphase present) > Ar-Cl (minor amount of microphase).

Synthesis and a combined experimental/theoretical structural study of a comprehensive set of Pd/NHC complexes with -, -, and -halogen-substituted aryl groups (X = F, Cl, Br, CF).

Pd/NHC complexes (NHCs - -heterocyclic carbenes) with electron-withdrawing halogen groups were prepared by developing an optimized synthetic procedure to access imidazolium salts and the corresponding metal complexes. Structural X-ray analysis and computational studies have been carried out to evaluate the effect of halogen and CF substituents on the Pd-NHC bond and have provided insight into the possible electronic effects on the molecular structure. The introduction of electron-withdrawing substituents changes the ratio of σ-/π-contributions to the Pd-NHC bond but does not affect the Pd-NHC bond energy.

Synthesis and characterization of Pd/NHC complexes with fluorinated aryl groups.

The key problem of the instability of fluorine-containing diazadienes was addressed to perform the efficient synthesis of imidazolium salts containing fluorine substituents in the aryl groups. The subsequent reaction of fluorine-containing imidazolium compounds (NHC) with palladium salts under simple conditions afforded new Pd/NHC complexes. Computational and structural studies were performed to assess the effect of fluorine on the Pd-NHC bond and gave insight into the electronic effects in the molecule.

Acid-Base and Anion Binding Properties of Tetrafluorinated 1,3-Benzodiazole, 1,2,3-Benzotriazole and 2,1,3-Benzoselenadiazole.

The influence of fluorination on the acid-base properties and the capacity of structurally related 6-5 bicyclic compounds - 1,3-benzodiazole 1, 1,2,3-benzotriazole 2 and 2,1,3-benzoselenadiazole 3 to σ-hole interactions, i. e. hydrogen (1 and 2) and chalcogen (3) bondings, is studied experimentally and computationally.