Modular Establishment of a Diketopyrrolopyrrole‐Based Polymer Library via Pd‐Catalyzed Direct C–H (Hetero)arylation: a Highly Efficient Approach to Discover Low‐Bandgap Polymers

A concise, highly efficient palladium‐catalyzed direct C–H (hetero)arylation is developed to modularly assemble a diketopyrrolopyrrole ( DTDPP )‐based polymer library to screen low‐bandgap and near‐infrared (NIR) absorbing materials. The DTDPP ‐based copolymers P1 and P2 with an alternating donor–acceptor–donor–acceptor (D–A–D–A) sequence and the homopolymer P9 exhibit planarity and excellent π‐conjugation, which lead to low bandgaps (down to 1.22 eV) as well as strong and broad NIR absorption bands (up to 1000 nm).     

用ICP-AES测定三烷基氧膦-煤油中的Ru,Rh和Pd元素

使用Ru,Rh和Pd水溶液标准,选取乙醇作为稀释液,用ICP-AES测定三烷基氧膦(trialkyl phos-phine oxide,TRPO)-煤油体系中Ru,Rh和Pd。研究了溶液配制中30%TRPO-煤油(v/v)比例、水溶液比例和硝酸浓度对测定Ru,Rh和Pd的影响。选取30%TRPO-煤油在溶液中的体积比为10%,水溶液体积比为5%和溶液的硝酸浓度为0.20mol.L-1时,配制的溶液呈均一溶液,处于稳定状态。根据上述条件,建立了ICP-AES测定有机相30%TRPO-煤油中的Ru,Rh和Pd的分析方法。Ru,Rh和Pd的检测限分别为0.057,0.025和0.118mg.L-1。方法的相对标准偏差小于3%。此方法不仅用于30%TRPO-煤油中Ru,Rh和Pd的测定,也可用于其他有机相体系中Ru,Rh和Pd的测定。     

Influence of Pd precursors on the catalytic performance of Pd–H4SiW12O40/SiO2 in the direct oxidation of ethylene to acetic acid

The effects of palladium precursors (PdCl₂, (NH₄)₂PdCl₄, Pd(NH₃)₂Cl₂, Pd(NO₃)₂ and Pd(CH₃COO)₂) on the catalytic properties in the selective oxidation of ethylene to acetic acid have been investigated for 1.0 wt% Pd–30 wt% H₄SiW₁₂O₄₀/SiO₂. The structures of the catalysts were characterized using X-ray diffraction, N₂ adsorption, H₂-pulse chemical adsorption, infrared spectrometry of the adsorbed pyridine, H₂ temperature-programmed reduction and X-ray photoelectron spectroscopy. The present study demonstrates that the different palladium precursors can lead to the significant changes in the dispersion of palladium. It is found that Pd dispersion decreases as follows: PdCl₂ > (NH₄)₂PdCl₄ > Pd(NO₃)₂ > Pd(NH₃)₂Cl₂ > Pd(C₂H₃O₂)₂, which is nearly identical to the catalytic activity. This indicates that the dispersion of palladium plays an important role in the catalytic activity. Furthermore, density of Lewis (L) and Brönsted (B) acid sites are also strongly dependent on the palladium precursors. It is also demonstrated that an effective catalyst should possess a well combination of Brönsted acid sites with dispersion of palladium.     

Mechanistic insight into the preactivation of a modern palladium catalyst precursor in phosphine-free Heck reactions

Abstract  The use of well-defined trans-dichlorobis(diethanolamine-N)palladium(II) complex (trans-[PdCl₂(DEA)₂]) as a new, modern, and effective Heck precatalyst is reported. The mechanism of the key, initial steps of the reaction, i.e., the formation of the Pd(0) complex, is examined using density functional theory. Graphical abstract        

Pd(0) or Pd(II)-catalyzed ring-opening reactions of benzylidene- and alkylidenecyclopropyl ketones and aldehydes

Pd(0) catalyzed reactions of methylenecyclopropyl carbonyl compounds afforded a convenient method for the synthesis of conjugate (E,E)-1,3-diene derivatives 2 in good to excellent yields. Moreover, we also found that Pd(II)-catalyzed reactions of methylenecyclopropyl carbonyl compounds with water gave 1,5-diketones in good to high yields via a carbene-palladium intermediate. The plausible reaction mechanisms have also been provided on the basis of control and ¹⁸O-labeling experiments.     

Size controlled synthesis of Pd nanoparticles in water and their catalytic application in C-C coupling reactions

Catalytically active Pd nanoparticles have been synthesized in water by a novel reduction of Pd(II) with a Fischer carbene complex where polyethylene glycol (PEG) was used as stabilizer. PEG molecules wrap around the nanoparticles to impart stability and prevent agglomeration, yet leave enough surface area available on the nanoparticle for catalytic activity. Our method is superior to others in terms of rapid generation and stabilization of Pd nanoparticles in water with a cheap, readily available PEG stabilizer. The size of the nanoparticles generated can be controlled by the concentration of PEG in water medium. The size decreased with the increase in the PEG: Pd ratio. This aqueous nano-sized Pd is a highly efficient catalyst for Suzuki, Heck, Sonogashira, and Stille reaction. Water is used as the only solvent for the coupling reactions.     

Ammonia gas sensor based on a spinel semiconductor,Co<Subscript>0.8</Subscript>Ni<Subscript>0.2</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanomaterial

Thick film of nanocrystalline Co_0.8Ni_0.2Fe₂O₄ was obtained by sol–gel citrate method for gas sensing application. The synthesized powder was characterized by X-ray diffraction (XRD) and transmission electron microscopy. The XRD pattern shows spinel type structure of Co_0.8Ni_0.2Fe₂O₄. XRD of Co_0.8Ni_0.2Fe₂O₄ revels formation of solid solution with average grain size of about 30 nm. From gas sensing properties it observed that nickel doping improves the sensor response and selectivity towards ammonia gas and very low response to LPG, CO, and H₂S at 280 °C. Furthermore, incorporation of Pd improves the sensor response and stability of ammonia gas and reduced the operating temperature upto 210 °C. The sensor is a promising candidate for practical detector of ammonia.     

Pd/SWNTs负载型催化剂的制备及其催化性能

利用单壁碳纳米管(SWNTs)自身的还原性, 将PdCl2溶液中的Pd2+直接还原成金属Pd负载在SWNTs表面上, 制备了具有良好催化性能的Pd/SWNTs负载型催化剂. 通过透射电镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和热重分析(TG)对Pd/SWNTs 进行了表征, 并利用Suzuki反应对Pd/SWNTs的催化性能进行了测试. 实验结果表明, 用SWNTs与12 mmol·L-1的PdCl2的水溶液直接作用, 得到Pd/SWNTs催化材料的Pd负载量达到14.13%(w, 质量分数), 颗粒分散均匀, 粒径小(2 nm左右), 与SWNTs结合紧密; 用经过H2还原的Pd/SWNTs作催化剂, 在90 ℃下进行Suzuki反应, 30 min后反应就基本完成, 其联苯的产率达到98.10%, 催化活性较高, 可望广泛用于有机合成反应.     

pd(Ⅱ)-A(bpy、trp)-ATP~(4-)体系混配合物的稳定性

用pH电位法测定40%(V/V)二(口恶)烷-水介质中(I=0.1,25±0.1℃)Pd(Ⅱ)A(bpy、trp~-)-ATP~(4-)体系形成三元混配合物Pd(bpy)(ATP)~(2-)和Pd(trp)(ATP)~3的稳定常数,其lgK_(Pd(A)(ATP)~(2-))~(Pd(A))值分别为5.16和4.11,Jlgk值为-0.02和-1.08,并与lgK_(Pd(phen)(ATP)~(2-))~(Pd(A))-作了比较,其稳定顺序为Pd(phen)(ATP)~(2-)〉Pd(bpy)(ATP)~2〉Pd(trp)(ATP)~(3-).这一变化规律可从配体间πA～πB的合作效应及配体A和ATP~4间芳环堆积作用获得满意解释.