Catalytic Activity In Heck Reaction Research Articles

Palladium nanoparticles embedded chitosan/poly(vinyl alcohol) composite nanofibers as an efficient and stable heterogeneous catalyst for Heck reaction

ABSTRACTIn this study, palladium nanoparticles were successfully embedded into modified chitosan/poly(vinyl alcohol) composite nanofibers (Pd‐CS/PVA nanofibers) by electrospinning. Then, the Pd‐CS/PVA nanofibers were treated at evaluated temperature to improve its solvent resistance and in situ reduce Pd2+ cations into Pd0 active species. The incorporated palladium nanoparticles with ultra small mean diameter of 3.73 ± 1.04 nm are evenly distributed inside the Pd‐CS/PVA nanofiber. The resulting Pd‐CS/PVA nanofiber mat exhibits high catalytic activity for Heck reaction of aromatic iodides with alkenes and can be recycled for 18 times without loss of initial activity. The high catalytic activity and stability of Pd‐CS/PVA nanofiber mat can be attributed to the ultra small diameter nanofibers, strong chelating ability of chitosan, and fine embedment of palladium species inside the nanofiber. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48026.

Synthesis of (Ph3P)2PdX2 complexes and their catalytic activity for Heck reaction involving aryl halide and acrylate

Two palladium complexes, (Ph3P)2PdBr2 and (Ph3P)2PdI2, were synthesized by a new method and their structures were confirmed by NMR, elemental analysis and X-ray crystallography. The catalytic activity of the two palladium complexes was evaluated in Mizoroki-Heck cross-coupling reaction of aryl halide with acrylate, the results show that they all have high catalytic activity to many different substrates.

A Facile Route for Production of CexOy Modified Carbon Fiber Supported Pd Nanoparticles and Their Highly Efficient Catalytic Activity for Heck Reaction

The highly-efficient carbon nanofibers supported CexOy–Pd NPs catalyst for catalyzing the Heck reaction by the electrospinning technique, hydrogenation reduction and subsequent calcination processes were prepared. The CexOy–Pd NPs/CNFs have enhanced catalytic activity compared with the Pd NPs/CNFs. The CexOy could play an auxiliary role in the catalytic process.

Synthesis of Palladium Nanocubes/Nanorods and Their Catalytic Activity for Heck Reaction of Iodobenzene

Palladium has been used as a catalyst not only in Suzuki and Heck cross coupling reaction in organic chemistry, but also in automobile industry for the reduction of vehicle exhausts. The catalytic activity of Pd nanoparticles depends strongly on their size and exposed crystalline facets. In this study, the single crystalline palladium nanocubes/nanorods were prepared in the presence of polyvinyl pyrrolidone (PVP) and potassium bromide (KBr) using the polyol method. Selected area diffraction pattern and high-resolution transmission electron microscopy (TEM) were performed by TEM. The result shows that the ratio of KBr/PVP is the key factor to determine whether the product is cubes or rods. The as-prepared Pd nanocubes were highly uniform in both size and shape. The ordered packing structures including monolayer and multilayer can be fabricated via the rate-controlled evaporation of solution solvent. The catalytic activity of these Pd nanocubes towards heck reaction of iodobenzene with acrylate or acrylic acid was found to be higher than that of Pd nanorods. We suspect it is caused by the difference of energy state while Pd nanocubes is {100} plane and nanorods is {111} plane.

The Performance of Au-Pd/Ni-Al-O for Heck Reaction

Au-Pd alloy nanoparticles supported on Ni-Al mixed oxide were prepared by impregnation-reduction method. Characterizations of the catalysts were applied by X-ray diffraction and UV-Vis spectrum. The bimetallic catalysts exhibited excellent catalytic activity in Heck reaction under mild conditions. Due to the easy separation of solid catalyst, it is thought as environmental friendly and these catalysts will be potential material in the synthesis of fine chemistry.

Palladium Nanoparticles Supported on Mixed‐Linker Metal–Organic Frameworks as Highly Active Catalysts for Heck Reactions

AbstractWell‐dispersed palladium nanoparticles (Pd NPs) supported on amine‐functionalized, mixed‐linker metal–organic frameworks (MIXMOFs) based on MIL‐53(Al) were prepared by using the ion‐exchange method. Pd NPs were characterized by powder X‐ray diffraction (XRD), N2 adsorption, transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectroscopy (ICP‐AES), and X‐ray photoelectron spectroscopy (XPS). The mean diameter of Pd NPs is approximately 3.2 nm. It was found that the Pd NPs supported on amine‐functionalized MIXMOFs are stable at high temperature. The Pd NPs exhibit efficient catalytic activity for Heck reaction and can be easily recovered and reused.

Preparation of microcapsule-supported palladium catalyst using SPG (Shirasu Porous Glass) emulsification technique

A new method for the preparation of microcapsule-supported palladium catalyst was described. The highly monodisperse cross-linked polystyrene microcapsules containing phosphine ligand were synthesized by the self-assembling of phase separated polymer (SaPSeP) method using diphenyl(4-vinylphenyl)phosphine and divinylbenzene as a monomer and crosslinking agent, respectively, and 2,2′-azobisisobutyronitrile (AIBN) as an initiator within the droplets of oil-in-water (O/W) emulsions, which were prepared by using the Shirasu Porous Glass (SPG) membrane emulsification technique. The prepared microcapsule-supported palladium catalyst exhibited high catalytic activity for Heck reaction and can be reused several times without loss of activity.

Nanoparticles of Pd on Hybrid Polyoxometalate−Ionic Liquid Material: Synthesis, Characterization, and Catalytic Activity for Heck Reaction

By partial exchange of surface protons of a polyoxometalate (POM; H5PO40V2Mo10) by an ionic liquid (IL; butylmethylimidazolium, bmim+), a protonic IL-POM ([bmim]4HPO40V2Mo10) was obtained. Further exchange of this material with Pd2+ yields a final solid that HRTEM and EXAFS-XANES techniques show to be formed by very regular nanoparticles of PdO with ∼2 nm diameter, which are supported on 1 μm particles of IL-POM hybrid material. The PdO nanoparticles can be easily reduced to Pd, and the resultant material is an active and selective catalyst for the Heck reaction. The catalyst can be recycled, though metal leaching occurs in polar solvents. This can be an interesting material for performing Pd-catalyzed reactions in nonpolar solvents or for working in gas-phase reactions.

Novel Ag(I), Pd(II), Ni(II) complexes of N, N′-bis-(2,2-diethoxyethyl)imidazole-2-ylidene: Synthesis, structures, and their catalytic activity towards Heck reaction

Tetra-ether substituted imidazolium salts, LHX (where LH = N, N′-bis(2,2-diethoxyethyl)imidazolium cation and X = Br, BF 4, PF 6, BPh 4, NO 3 and NTf 2 anions) were derived from imidazole. Attempts to produce aldehyde functionalized imidazolium salt through acid hydrolysis of LHBr resulted an unexpected tetra-hydroxy compound L AHBr and the dialdehyde compound L BHBr. Reaction of LHBr with Ag 2O afforded [L 2Ag][AgBr 2] ( 1). Mononuclear Pd-complex trans-[L 2PdCl 2] ( 2) and dinuclear Pd-complex [(LPdCl 2) 2] ( 3) were obtained by 1:1 and 1:2 reaction of in situ generated Ag-carbene with Pd(CH 3CN) 2Cl 2. cis-[LPdPPh 3Cl 2] ( 4) was synthesized from reaction of PPh 3 with dinuclear complex 3. Hydrolysis of 3 under acidic conditions also generates a hydroxy derivative 3A and the aldehyde derivative 3B. Direct heating of LHBr with Ni(OAc) 2 · 4H 2O at 120 °C under vacuum generated trans-[L 2NiBr 2] ( 5). These complexes were characterized by NMR, mass, elemental analysis, and X-ray single crystal diffraction analysis. Pd--Pd interaction was observed in 3. All the Pd complexes exhibited excellent catalytic activity in Heck reaction.