Alkoxycarbonylation of Allyl Bromide over Palladium Catalyst in Different Reaction Mediums

Supercritical carbon dioxide(scCO2)and its subcritical analogue are now widely used as environ mentally-friendly substitutes of conventional organic solvents in chemical synthesis[1-4]     

Alkoxycarbonylation of Allyl Bromide over Palladium Catalyst in Different Reaction Mediums

Supercritical carbon dioxide(scCO2)and its subcritical analogue are now widely used as environ mentally-friendly substitutes of conventional organic solvents in chemical synthesis[1-4]     

Effect of Co-solvent on the Palladium Catalyzed Alkoxycarbonylation of Allyl Bromide in Supercritical CO_2

We have studied the palladium-catalyzed alkoxycarbonylation of allyl bromide in supercritical (sc) CO2 and found the reaction rate in sc CO2 was lower than those in some organic solvents1. The possible reason was the lower solubility of sc CO2 for the palladium catalyst. As an effective approach to improve the solubility of varieties of solutes, cosolvent such as ethanol has been widely used in the sc CO2 extraction2,3. Based on the above consideration, we chose several organic reagents…     

Palladium Catalyzed Suzuki Cross-coupling Reaction in Molten Tetra-n-butylammonium Bromide

A practical procedure for palladium catalyzed Suzuki cross-coupling reaction of arylboronic acids with aryl halides, including aryl chlorides in molten tetra-n-butylammonium bromide (TBAB) was developed. The reaction exhibits high efficiency and functional group tolerance. The recovery of the catalyst and molten n-Bu4NBr was also investigated.     

果胶负载钯催化剂的制备及Suzuki反应催化性能

以柑橘皮果胶为载体,采用吸附法制备了果胶负载钯催化剂,并将其应用于四苯硼钠与溴代芳烃的交叉偶联反应中.该反应体系以聚乙二醇400(PEG 400)/H2O为反应溶剂,三乙胺为碱,在空气中于110℃反应15~60 min,四苯硼钠中4个苯基均可顺利参与反应,高产率地获得相应的目标化合物.该方法具有条件温和、反应时间短、收率高且催化剂可循环利用等优点.     

负载钯催化剂上亚硝酸乙酯的催化分解

 研究了亚硝酸乙酯在不同载体及负载钯催化剂上的分解行为．结果显示,固体酸性中心和金属钯中心都可以催化亚硝酸乙酯的分解反应．在C2H5ONO与CO合成草酸二乙酯的反应中,亚硝酸乙酯是在固体催化剂表面发生分解,而不是在气相发生热裂解．并且,该反应的活性与亚硝酸乙酯的分解程度不存在正比关系．通过对分解产物的分析,提出了亚硝酸乙酯在固体催化剂上分解的连续脱氢机理．     

Catalyst Activity and Selectivity in the Isomerising Alkoxycarbonylation of Methyl Oleate

The synthesis of unsymmetrical diphosphine ligands ( 3 a – g ) with an o‐tolyl backbone and tert‐butyl, adamantyl, cyclohexyl and isopropyl substituents on the phosphorus moiety is described (1,2‐(CH₂PR₂)(PR′₂)C₆H₄; 3 a : R=tBu, R′=tBu, 3 b : R=tBu, R′=Cy, 3 c : R=tBu, R′=iPr, 3 d : R=Ad, R′=tBu, 3 e : R=Ad, R′=Cy, 3 f : R=Cy, R′=Cy, 3 g : R=Ad, R′=Ad). The corresponding diphosphine–Pd^II ditriflate complexes [(P^P)Pd(OTf)₂] ( 5 a – g ) were prepared and structurally characterised by X‐ray crystallography. These new complexes were studied as catalyst precursors in the isomerising methoxycarbonylation of methyl oleate, and were found to convert methyl oleate into the corresponding linear α,ω‐diester ( L ) with 70–80 % selectivity. The products of this catalytic reaction with the known [{1,2‐(tBu₂PCH₂)₂C₆H₄}Pd(OTf)₂] complex ( 5 h ) were fully analysed, and revealed the formation of the linear α,ω‐diester ( L , 89.0 %), the methyl‐branched diester B1 (4.3 %), the ethyl‐branched diester B2 (1.0 %), the propyl‐branched diester B3 (0.6 %) and all diesters from butyl‐ to hexadecyl‐branched diesters B4 – B16 (overall 4.8 %) at 90 °C and 20 bar CO. The productivity of the catalytic conversion of methyl oleate with complexes 5 a – g varied with the steric bulk of the alkyl substituent on the phosphorus. Ligands with more bulky groups, like tert ‐ butyl or adamantyl (e.g., 5 a , 5 d , 5 g ), were more productive systems. The formation of the catalytically active hydride species [(P^P)Pd(H)(MeOH)]⁺ ( 6‐MeOH ) was investigated and observed directly for complexes 5 a – e and 5 g , respectively. These hydride species were isolated as the corresponding triphenylphosphine complexes ( 6‐PPh₃ ) and fully characterised, including by X‐ray crystallography. The catalytic productivity of 6 a‐PPh₃ was virtually identical to that of 5 a , thereby confirming the efficient hydride formation of 5 a under catalytic conditions.     

Suzuki Reaction of Aryl Bromides Using a Phosphine-Free Magnetic Nanoparticle-Supported Palladium Catalyst

A palladium catalyst immobilized on superparaganetic nanoparticles was prepared with a palladium loading of 0.30 mmol/g. The catalyst was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, thermogravimetric analysis, Fourier transform infrared, atomic absorption spectrophotometry, and nitrogen adsorption. The immobilized palladium catalyst was an efficient catalyst without added phosphine ligands for the Suzuki cross-coupling reaction of several aryl bromides with phenylboronic acid. The recovery of catalyst was simply by magnetic decantation in the presence of a magnet. The immobilized palladium catalyst can be reused many times without significant degradation in catalytic activity. No leaching of active palladium species into the reaction solution was detected.     

Density Functional Theory Analysis of Anthraquinone Derivative Hydrogenation over Palladium Catalyst

A density functional theory (DFT) analysis was conducted on the hydrogenation of 2‐alkyl‐anthraquinone (AQ), including 2‐ethyl‐9,10‐anthraquinone (eAQ) and 2‐ethyl‐5,6,7,8‐tetrahydro‐9,10‐anthraquinone (H₄eAQ), to the corresponding anthrahydroquinone (AQH₂) over a Pd₆H₂ cluster. Hydrogenation of H₄eAQ is suggested to be more favorable than that of eAQ owing to a higher adsorption energy of the reactant (H₄eAQ), lower barrier of activation energy, and smaller desorption energy of the target product (2‐ethyl‐5,6,7,8‐tetrahydro‐9,10‐anthrahydroquinone, H₄eAQH₂). For the most probable reaction routes, the energy barrier of the second hydrogenation step of AQ is circa 8 kcal mol^?1 higher than that of the first step. Electron transfer of these processes were systematically investigated. Facile electron transfer from Pd₆H₂ cluster to AQ/AQH intermediate favors the hydrogenation of C=O. The electron delocalization over the boundary aromatic ring of AQ/AQH intermediate and the electron‐withdrawing effect of C=O are responsible for the electron transfer. In addition, a pathway of the electron transfer is proposed for the adsorption and subsequent hydrogenation of AQ on the surface of Pd₆H₂ cluster. The electron transfers from the abstracted H atom (reactive H) to a neighbor Pd atom (Pd_H), and finally goes to the carbonyl group through the C₄ atom of AQ aromatic ring (C₄).     

Oxidative Esterification of Methacrolein to Methyl Methacrylate over Supported Palladium Catalyst

Methyl methacrylate (MMA) is an important monomer, widely used for producing acrylic plastics, polymer dispersions for paints and coatings. Traditional acetone cyanhydrin (ACH) method involves toxic hydrogen cyanide and a large quantity of ammonium bisulf…     

高分子载钯催化剂对有机锡烷偶联反应的催化性能及结构表征

制备了几种负载型钯催化剂，用于有机锡烷与有机卤化物的偶联反应中，考察了催化剂的使用寿命及载体对催化剂催化活性的影响，通过XPS、XRD、电镜等技术对催化剂进行了表征。结果表明，催化活性中心的质点钯是金属态钯，即催化剂中的钯可以看成是两配位不饱和的，经过氧化加成、金属转换、还原消除过程完成催化反应。     

Defect Rich Structure Activated 3D Palladium Catalyst for Methanol Oxidation Reaction

Controlling the structure and properties of catalysts through atomic arrangement is the source of producing a new generation of advanced catalysts. A highly active and stable catalyst in catalytic reactions strongly depends on an ideal arrangement structure of metal atoms. We demonstrated that the introduction of the defect-rich structures, low coordination number (CN), and tensile strain in three-dimensional (3D) urchin-like palladium nanoparticles through chlorine bonded with sp-C in graphdiyne (Pd-UNs/Cl-GDY) can regulate the arrangement of metal atoms in the palladium nanoparticles to form a special structure. In situ Fourier infrared spectroscopy (FTIR) and theoretical calculation results show that Pd-UNs/Cl-GDY catalyst is beneficial to the oxidation and removal of CO intermediates. The Pd-UNs/Cl-GDY for methanol oxidation reaction (MOR) that display high current density (363.6 mA cm⁻²) and mass activity (3.6 A mg_Pd⁻¹), 12.0 and 10.9 times higher than Pd nanoparticles, respectively. The Pd-UNs/Cl-GDY catalyst also exhibited robust stability with still retained 95 % activity after 2000 cycles. A defects libraries of the face-centered cubic and hexagonal close-packed crystal catalysts (FH-NPs) were synthesized by introducing chlorine in graphdiyne. Such defect-rich structures, low CN, and tensile strain tailoring methods have opened up a new way for the catalytic reaction of MOR.     

木质素负载钯催化剂的制备及对Heck反应的催化性能

以天然木质素和PdC l2为原料,合成了木质素负载钯催化剂,用IR、XPS、TG、DTA等对其进行了表征.研究表明,该催化剂在空气氛围中能催化丙烯酸与芳基碘的Heck反应,并有一定的重复使用性能.     

壳聚糖席夫碱钯催化碘代苯与丙烯酸乙酯反应

以水杨醛与壳聚糖反应制得的壳聚糖席夫碱配体再与PdCl2反应制得了壳聚糖席夫碱钯催化剂。研究了该催化剂对碘代苯(PhI)与丙烯酸乙酯(EA)偶联生成反式肉桂酸乙酯反应的催化性能。考察了原料比、缚酸剂种类及其用量、反应温度、溶剂、催化剂用量、反应时间等因素对该反应的影响,确定了该催化反应的最佳反应条件。该催化剂经过滤分离、溶剂洗涤,循环使用4次仍有较高的催化活性。     

淀粉负载钯催化剂的制备及对Heck反应的催化性能

淀粉负载钯催化剂的制备及对Heck反应的催化性能;淀粉;钯;负载型催化剂;Heck反应     

Cyclization-Carbonylation-Cyclization Coupling Reaction of Propargyl Ureas with Palladium(II)-Bisoxazoline Catalyst

The cyclization-carbonylation-cyclization coupling reaction (CCC-coupling reaction) of propargyl ureas catalyzed by Pd^II(box) complexes afforded symmetrical ketones bearing two 2-amino-2-oxazoline groups in good to moderate yields.     

Electrothermal Water-Gas Shift Reaction at Room Temperature with a Silicomolybdate-Based Palladium Single-Atom Catalyst

The water-gas shift (WGS) reaction is often conducted at elevated temperature and requires energy-intensive separation of hydrogen (H₂) from methane (CH₄), carbon dioxide (CO₂), and residual carbon monoxide (CO). Designing processes to decouple CO oxidation and H₂ production provides an alternative strategy to obtain high-purity H₂ streams. We report an electrothermal WGS process combining thermal oxidation of CO on a silicomolybdic acid (SMA)-supported Pd single-atom catalyst (Pd₁/CsSMA) and electrocatalytic H₂ evolution. The two half-reactions are coupled through phosphomolybdic acid (PMA) as a redox mediator at a moderate anodic potential of 0.6 V (versus Ag/AgCl). Under optimized conditions, our catalyst exhibited a TOF of 1.2 s⁻¹ with turnover numbers above 40 000 mol mol_Pd⁻¹ achieving stable H₂ production with a purity consistently exceeding 99.99 %.     

A Supported Palladium on Gallium-based Liquid Metal Catalyst for Enhanced Oxygen Reduction Reaction

Developing high-performance catalysts for oxygen reduction reaction to replace costly platinum-based materials is of great importance but still confronted with challenges. Herein, a kind of supported palladium liquid metal catalyst, which is prepared by galvanic replacement, surpasses commercial Pt/C and Pd/C in oxygen reduction catalysis with a higher half-wave potential of 0.92 V, mass activity of 1.85 A/mg_Pd at 0.90 V, and superior durability. The liquid metal support can both optimize the electronic structures of Pd sites and guarantee the dispersion of Pd atoms, which explains the enhanced activity and durability, respectively. This work opens an avenue for rational design of catalysts.     

Water Soluble Starch Stabilized Palladium Nanoparticle: Efficient Catalyst for Miyaura-Suzuki Coupling Reaction

The fabricated water soluble starch stabilized palladium nanoparticle promoted Miyaura‐Suzuki coupling reaction with high catalytic activity and selectivity and in excellent yields, which include recovery and re‐use of this catalyst at least three times.