Heterogeneous versus Homogeneous Palladium Catalysts for Cross-Coupling Reactions

Utility of a heterogeneous palladium catalyst for the synthesis of a molecular semiconductor via Stille, Suzuki, and direct heteroarylation cross-coupling reactions

Demonstration of the utility of a commercially available heterogeneous palladium catalyst in the synthesis of a relevant high performance molecular semiconductor.

Dendrimer-encapsulated Pd nanoparticles as catalysts for C–C cross-couplings in flow microreactors

Dendrimer-encapsulated Pd nanoparticles anchored within continuous flow microreactors are efficient for C–C cross-coupling reactions. This is witnessed by the good catalytic performance for the Heck–Cassar and Suzuki–Miyaura couplings.

Versatile functionalization of carbon electrodes with a polypyridine ligand: metallation and electrocatalytic H+ and CO2 reduction

A carbon electrode is functionalized with a polypyridine ligand and subsequently metallated to catalyze the electroreduction of H⁺ and CO₂.

Heterogeneous Cu/OMS-2 as an efficient catalyst for the synthesis of tetrasubstituted 1,4-enediones and 4H-pyrido[1,2-a]-pyrimidin-4-ones

Copper supported on OMS-2: a heterogeneous catalyst Cu/OMS-2 was prepared for the synthesis of tetrasubstituted 1,4-enediones and 4H-pyrido[1,2-a]-pyrimidin-4-ones under the same conditions with air as the oxidant.

Thermoregulated Aqueous Biphasic Catalysis of Sonogashira Reactions

A water-based thermoregulated system for Pd-catalyzed Sonogashira reactions is presented, which allows for not only a highly efficient homogeneous catalytic reaction, but also an easy separation/recovery of the catalyst. The novel catalytic system exhibits high efficiency and excellent reusability. In addition, the Sonogashira reactions are performed with Pd(OAc)2 without a copper co-catalyst.

Controlled synthesis of uniform palladium nanoparticles on novel micro-porous carbon as a recyclable heterogeneous catalyst for the Heck reaction

Highly dispersed palladium nanoparticles encaged by micro-porous carbon exhibit excellent cycling performance towards the Heck cross-coupling reaction.

Clean and fast cross-coupling of aryl halides in one-pot

Unsymmetrically coupled biaryls are synthesized in high yield starting from different aryl bromides and bis(pinacolato)diboron by carrying out the Miyaura borylation reaction followed by the Suzuki–Miyaura reaction in the same reaction pot over 1–2 mol % SiliaCat DPP-Pd. The SiliaCat DPP-Pd catalyst is air-stable and the method does not require the use of inert conditions. The use of non-toxic isopropanol or 2-butanol as reaction solvent further adds to the environmental benefits of this new green synthetic methodology.

A highly Lewis-acidic Pd(iv) surface on Pd@SiO2 nanocatalysts for hydroalkoxylation reactions

The Pd(iv) species, generated on the surface of Pd@SiO₂ nanocatalysts via oxidation with iodobenzene dichloride (PhICl₂) or N-chlorosuccinimide (NCS), showed high reactivity and superior stability for hydroalkoxylation reactions.

Sustainable catalysis: rational Pd loading on MIL-101Cr-NH2 for more efficient and recyclable Suzuki-Miyaura reactions

Palladium nanoparticles have been immobilized into an amino-functionalized metal-organic framework (MOF), MIL-101Cr-NH2, to form Pd@MIL-101Cr-NH2. Four materials with different loadings of palladium have been prepared (denoted as 4-, 8-, 12-, and 16 wt%Pd@MIL-101Cr-NH2). The effects of catalyst loading and the size and distribution of the Pd nanoparticles on the catalytic performance have been studied. The catalysts were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), N2-sorption isotherms, elemental analysis, and thermogravimetric analysis (TGA). To better characterize the palladium nanoparticles and their distribution in MIL-101Cr-NH2, electron tomography was employed to reconstruct the 3D volume of 8 wt%Pd@MIL-101Cr-NH2 particles. The pair distribution functions (PDFs) of the samples were extracted from total scattering experiments using high-energy X-rays (60 keV). The catalytic activity of the four MOF materials with different loadings of palladium nanoparticles was studied in the Suzuki-Miyaura cross-coupling reaction. The best catalytic performance was obtained with the MOF that contained 8 wt% palladium nanoparticles. The metallic palladium nanoparticles were homogeneously distributed, with an average size of 2.6 nm. Excellent yields were obtained for a wide scope of substrates under remarkably mild conditions (water, aerobic conditions, room temperature, catalyst loading as low as 0.15 mol%). The material can be recycled at least 10 times without alteration of its catalytic properties.

Chiral metal nanoparticle-catalyzed asymmetric C-C bond formation reactions

Chiral ligand-modified metal nanoparticles possess an attractive potential for application in asymmetric synthesis. This article focuses on chiral-nanoparticle-catalyzed asymmetric C-C bond formation reactions and discusses the nature of the active species.

The sol-gel entrapment of noble metals in hybrid silicas: a molecular insight

BACKGROUND

Why are metal nanoparticles sol-gel entrapped in ORMOSIL so active and stable? In other words, why ORMOSIL-entrapped metal nanoparticles are more active and selective than many heterogenized counterparts, including silica-entrapped noble metals?

RESULTS

Unveiling specific interactions between MNPs and the molecular structure of ORMOSIL, this work investigates subtle structural aspects through DRIFT spectroscopy.

CONCLUSIONS

The results point to interactions between entrapped Pd and Pt nanocrystallites with the organosilica sol-gel cages similar to those taking place in enzymes.

Cross-coupling of alkyl halides with aryl or alkyl Grignards catalyzed by dinuclear Ni(II) complexes containing functionalized tripodal amine-pyrazolyl ligands

Structurally distinctive dinuclear Ni(II) complexes with furan or thiophene tethered amine-pyrazolyl tripodal hybrid ligands have been synthesized and crystallographically characterized. All complexes are catalytically active towards cross-coupling of aryl/alkyl Grignard reagents with β-H containing alkyl halides at room temperature in the presence of N,N,N',N'-tetramethylethylenediamine (TMEDA). The catalytic efficacy of the complexes is dependent on the tether substituent at the central amine. Two species, Ni(II) TMEDA and Mg(II) TMEDA complexes, have been isolated from the catalytic reaction mixtures under different conditions. Some ligand-stabilized Ni(II) and Mg(II) bimetallic species have also been identified in the ESI-MS spectra.