A highly efficient polymer‐anchored palladium(II) complex catalyst for hydrogenation,Heck cross‐coupling and cyanation reactions

BACKGROUND: Precise architectures of steric and electronic properties of palladium species play a crucial role in designing highly functionalized catalyst systems responsible for target organic transformations. Pd catalysts supported on polymer materials have been employed extensively as catalysts not only for hydrogenation but also for coupling reactions in the production of fine chemicals. RESULTS: A new polymer‐anchored Pd(II) complex has been synthesized and characterized. The catalyst shows high catalytic activity in the hydrogenation of styrene oxide, Heck cross‐coupling and cyanation reactions of aryl halides. The effect of various reaction parameters were investigated to optimize reaction conditions. The catalytic system shows good activity in the hydrogenation of styrene oxide (conversion 98%) with a selectivity to 2‐phenylethanol (93%) which is higher than its homogeneous analogues. The catalyst also exhibits excellent catalytic activity for the Heck cross‐coupling and cyanation reactions of various substituted and non‐substituted aryl halides. CONCLUSIONS: Results demonstrate that the catalyst is robust and stable and can be recovered quantitatively by simple filtration and reused several times without loss of activity. Copyright © 2010 Society of Chemical Industry     

催化剂种类对液相氢还原法制备超细镍粉的影响

以硫酸镍为原料,研究不同催化剂对液相氢还原法制备超细镍粉的作用效果,重点研究了催化剂用量对还原率的影响。结果表明,添加催化剂可以促进液相氢还原反应的进行,缩短反应时间,提高单位时间内氢氧化 镍浆液还原成金属镍粉的还原率;活性镍粉、PdCl₂、RuCl₃及蒽醌4种催化剂对比实验结果表明,使用质量浓度为 10 mg/L的PdCl₂作为催化剂配料,可以使硫酸镍液相氢还原反应制备超细镍粉在最短时间内到达最高的还原率。     

Pd(0)-<Emphasis Type="Italic">S</Emphasis>-methylisothiourea grafted onto mesoporous MCM-41 and its application as heterogeneous and reusable nanocatalyst for the Suzuki,Stille and Heck cross coupling reactions

In this project palladium (0) S-methylisothiourea was grafted into MCM-41 mesoporous silica. Palladium (0) S-methylisothiourea complex supported on MCM-41 (Pd(0)-SMT-MCM-41), as heterogeneous and reusable catalyst, was used in C–C bond formation between various aryl halides with sodium tetraphenylborate or phenylboronic acid (Suzuki reaction), aryl halides with triphenyltin chloride (Stille reaction), and aryl halides with styrene or n-butyl acrylate (Heck reaction). This catalyst was characterized by various physico-chemical techniques such as X-ray diffraction, transmission electron microscopy, scanning electron microscopy (SEM/EDX), thermal gravimetric analysis (TGA/DTA), fourier transform infrared spectroscopy and inductively coupled plasma. The results indicated that Pd(0)-SMT-MCM-41 catalyst could be easily recovered from reaction mixture for several consequence runs without significant loss of its catalytic activities.     

Gold compounds as efficient co-catalysts in palladium-catalysed alkynylation

A series of inorganic and organometallic compounds of gold [AuCl(tht)], [Au(C₆F₅)(tht)] and Na[AuCl₄] (tht = tetrahydrothiophene) are shown to efficiently co-catalyze the Sonogashira-type cross-coupling reaction of phenylacetylene with aryl halides in THF solution. [AuCl(tppts)] (tppts = trisodium salt of tris(m-sulfonatophenyl)phosphine) co-catalyzes the same reaction in biphasic aqueous systems. Gold compounds are thus revealed as efficient transmetalation catalysts to palladium.     

Thiosemicarbazone Salicylaldiminato‐Palladium(II)‐Catalyzed Mizoroki–Heck Reactions

Four tridentate thiosemicarbazone salicylaldiminato‐palladium(II) complexes of the general formula [Pd(saltsc‐R)PPh₃] [saltsc=salicylaldehyde thiosemicarbazone; R=H ( 1 ), 3‐tert‐butyl ( 2 ), 3‐methoxy ( 3 ), 5‐chloro ( 4 )], have been evaluated as catalyst precursors for the Mizoroki–Heck coupling reaction between a variety of electron‐rich and electron‐poor aryl halides and olefins. The palladium complexes (0.1–1 mol% loading) were found to effectively catalyze these reactions with high yields being obtained when aryl iodides and aryl bromides were utilized. The effects of base, catalyst loading, reaction temperature and reaction time on the catalytic activity of the most active complex were also investigated.     

A Reusable Polymer-Anchored Palladium(II) Schiff Base Complex Catalyst for the Suzuki Cross-Coupling,Heck and Cyanation Reactions

A new polymer-anchored Pd(II) complex has been synthesized, characterized and its catalytic activity was investigated for the Suzuki cross-coupling reaction between aryl halides and arylboronic acid in the presence of K₂CO₃ as a base, for Heck olefination of aryl halides with alkenes, and for cyanation reaction of aryl iodides with K₄Fe(CN)₆ in presence of Et₃N as base. The key features of the catalyst include rapid reactions with excellent conversion without the use of phosphine ligands and total stability under the reactions conditions. The catalyst was recovered by simple filtration and reused five-times without significant loss of catalytic activity.     

A facile preparation of palladium Schiff base complex supported into MCM-41 mesoporous and its catalytic application in Suzuki and Heck reactions

A simple and efficient method for phosphine-free C–C coupling reactions such as Heck and Suzuki reactions in the presence of pyrrole Schiff base complex of palladium immobilized on mesoporous mesoporous of MCM-41 (Pd-Py-MCM-41) has been reported. The Suzuki reaction was carried out in PEG-400 using phenylboronic acid (PhB(OH)₂). Pd-Py-MCM-41 has been found as a promising catalyst for Heck reaction of butyl acrylate with aryl halides (including Cl, Br and I). The catalyst was characterized by FT-IR, TEM, XRD, SEM, BET and ICP-OES techniques. The protocol proves to be efficient and environmentally benign in terms of high yield, easy of recovery and reusability of catalyst.     

Fe3O4-carbon spheres core–shell supported palladium nanoparticles: A robust and recyclable catalyst for suzuki coupling reaction

Suzuki-Miyaura (S-M) is regarded the most powerful way for synthesis biaryls, triaryls, or incorporating of substituted aryl moieties in organic preparation by the cross-coupling of aryl boronic acid with aryl halides using the Pd catalyst. This work reports the combining of the hydrothermal and microwave-assisted protocol to convert the glucose to magnetic carbon spheres (Fe₃O₄-CSPs) decorated with Pd nanoparticles (NPs) as the catalyst for Suzuki-Miyaura cross-coupling reactions. The physicochemical properties in the produced composite were examined using FESEM, HRTEM, nitrogen isotherms, Raman spectroscopy, FTIR, XPS, and XRD. The as-fabricated composite Pd/Fe₃O₄-CSPs is mostly spherical with a core–shell structure and possesses a great surface area of 253.2 m²·g^-1. Its catalytic performance demonstrates that the composite has excellent stability and high tolerance Suzuki-Miyaura cross-coupling reactions in 30 min at 80 ℃. Both activated and deactivated aryl halides provided excellent yield. The as-fabricated catalyst was recycled for up to four catalytic cycles without a substantial decline in performance. Moreover, this research offers a facile roadmap for synthesizing Pd/Fe₃O₄-CSPs composites and promoting the practical implementation of Pd/Fe₃O₄-CSPs catalysts for organic transformation processes.     

纤维素负载三苯膦-钯复合物催化剂的合成及其对Heck偶联反应的催化性能研究

合成了一种新型的纤维素负载的三苯膦（Cell—OPPh3）,随后与醋酸钯反应生成了纤维素负载的三苯膦一钯复合物（Cell—OPPh3-Pd）催化剂,并对其进行了扫描电镜（SEM）、透射电镜（TEM）、热失重（TG）等分析表征。结果表明,催化刺对空气稳定,可有效催化空气条件下芳基卤和丙烯酸酯的Heck偶联反应。     

密闭空间CO消除的Pd/Al_2O_3催化剂合成及其催化性能研究

采用浸渍法制备不同PdCl_2含量的贵金属催化剂,并对反应前后催化剂进行傅里叶红外和物理结构表征。结果表明,PdCl_2质量分数为3%的催化剂活性最高,可在70℃实现低浓度CO的完全转化。反应后,催化剂表面没有明显变化,催化剂比表面积增大,孔容及平均孔径呈减小趋势。研究进口CO浓度和空速对CO转化率的影响,结果表明,在一定浓度范围,提高进口CO浓度对CO转化率没有影响,浓度超过1 000×10~(-6)时,CO转化率下降;空速升高,CO转化率下降,温度越低,空速对CO转化率影响越大。     

A novel thermo and pH-double sensitive hydrogel immobilized Pd catalyst for Heck and Suzuki reactions in aqueous media

A novel Hydrogel (1) was prepared from N-isopropylacrylamide, 4-vinylpyridine and potassium acrylate by free radical cross-linking polymerization. Hydrogel (1) showed both thermosensitivity and pH-sensitivity, and exhibited high swelling capacity in water. Because Hydrogel (1) has porous structure in its network and good loading performance with Pd²⁺, it was used as “microreactor” for immobilization of metal nanoparticles. We chose Heck and Suzuki reaction of aryl halides in water as test reaction to probe the catalytic activity of such Hydrogel (1) supported palladium catalyst. As a result, the Hydrogel (1)-Pd (II) catalyst exhibited good catalytic activity in both Heck and Suzuki reactions. Moreover, the Hydrogel (1)-Pd (II) catalyst was easily recovered and recycled. The reuse experiments showed that it was recycled six times without obviously losing of catalytic activity.     

A porous metal–organic framework as active catalyst for multiple C–N/C–C bond formation reactions

A 3D porous metal–organic framework {[Cu(4-tba)₂](solvent)}_n (1⋅S) is assembled via 4-(1H-1,2,4-triazol-1-yl)benzoic acid (Htba) and Cu(II) nodes, which shows the [2 + 2] roto-translational interpenetrating network. Interestingly, 1 displays high CO₂ adsorption selectivity over CH₄/H₂/O₂/Ar/N₂ gases, and acts an efficient catalyst precursor in some C–N/C–C bond formation reactions, including Chan–Lam coupling reaction of phenylboronic acid with imidazole, Suzuki–Miyoura coupling reaction of phenylboronic acids with aryl halides, and Heck coupling reaction of styrene with aryl halides.     

KINETIC STUDY OF SYNTHESIZING UNSYMMETRIC ACETALS UNDER PHASE TRANSFER CONDITIONS

An effective method was proposed to determine the two organic-phase rate constants of the primary and secondary reactions which have differences in rates. The goal was achieved by employing the reaction of two mixed l-alcohols and dibromomethane in an alkaline solution of KOH/chlorobenzene two-phase medium under phase transfer catalysis. A new product of unsymmetric acetal was obtained in this work. The intermediate ROCH₂Br (a-haloalkyl ether) was not detected during or after the reaction when using high reactive alcohols. This result indicated that ROCH2Br was more reactive than the organic reactant CH₂Br₂. This high reactive a-haloalkyl ether implied that the rate constants of secondary reactions are larger than those of the primary reactions. The resistance of mass transfer of the catalyst ((C₄H₉)₄NBr, QBr) and the active catalyst, ((C₄H₉ )₄NOR, QOR R: c₄h₉and C₈h₁₇) transferring from the aqueous phase to the organic-phase and vice versa were found to be negligible. The organic-phase reaction is a rate-determining step of the phase transfer catalytic reaction, A measured constant concentration of tetrabutylammonium alkoxide (QOR) during the reaction leads to the application of pseudo-first order rate law. The reaction rate constant of ROCh₂Br acts 10⁴ larger than that of CH₂Br₂.     

Heterogeneous Fe3O4@chitosan-Schiff base Pd nanocatalyst: Fabrication,characterization and application as highly efficient and magnetically-recoverable catalyst for Suzuki–Miyaura and Heck–Mizoroki C–C coupling reactions

An environmentally friendly palladium-based catalyst supported on magnetite nanoparticles was successfully prepared. FT-IR, XRD, VSM, SEM, EDS and TGA studies have been used to characterize the nanocatalyst. The catalytic activity of the as-prepared catalyst was evaluated as a heterogeneous catalyst for the Suzuki–Miyaura carbon–carbon cross-coupling reaction of aryl halides and phenylboronic acid. Furthermore, it was found that the catalyst showed a high activity for the Mizoroki–Heck reaction of aryl halides and n-butyl acrylate. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture and recycled consecutive five runs without any significant loss in activity.     

氧化石墨烯复合金属催化剂催化碳酸二甲酯合成反应性能

针对甲醇气相氧化羰基化直接合成碳酸二甲酯（DMC）反应中催化剂活性低和稳定性差的问题，制备了一系列氧化石墨烯复合金属催化剂，并对其进行活性评价。结果表明：催化剂PdCl₂-CuCl₂-KOAc/AC@GO-HCl表现出最佳的催化活性和稳定性：DMC的空时收率（STY）为800~900 g·(L cat)^-1·h^-1，且反应16 h内活性无明显下降；甲醇选择性保持在95%以上，CO选择性为35%~40%。结合XRD和XPS表征发现，活性物种Cu₂Cl(OH)₃的生成，提高了催化剂催化活性，而CuO和KCl均可导致催化剂的失活。     

Poly(o-toluidine) as the matrix for incorporation of palladium species from PdCl2 aqueous solutions

Reactivity of poly(o-toluidine) in the emeraldine base form (POT) and protonated with HCl (POT/HCl) in PdCl₂ aqueous solutions of various HCl concentrations has been studied. Using elemental analysis, FTIR, UV–Vis, XPS and EXAFS spectroscopies as well as XRD and SEM it has been established that POT/HCl is more reactive than POT. The course of reactions is influenced by the type of the PdCl₂ solution. Thus, protonation of POT with incorporation of palladium (II) chloro–and/or aquachloro–and/or chlorohydroxycomplexes counterions is the main process occurring in the PdCl₂ solutions of higher HCl concentration. A redox reaction resulting in the oxidation of the polymer chain with simultaneous formation of metallic palladium takes place in the PdCl₂ solution of lower HCl concentration. POT/HCl shows enhanced reducing properties with respect to POT. Lowering of the protonation level (i.e. some deprotonation) of POT/HCl has been also observed. Coordination of palladium (II) ions by nitrogen atoms of the polymer chain can be also postulated.     

Silica-supported poly-γ-methylselenopropylsiloxane palladium complex: An efficient catalyst for Heck carbonylation of aryl halides

A silica-supported poly-γ-methylselenopropylsiloxane palladium complex has been prepared from γ-chloropropyltriethoxysilane via immobilization on fumed silica, followed by reacting with sodium methylselenolate and then the reaction with palladium chloride. It is an efficient catalyst for Heck carbonylation of aryl halides under atmospheric pressure of carbon monoxide. This polymeric palladium catalyst can be recovered and reused.     

一种新γ相氧化铝负载的铁铝双金属催化剂用于反向水煤气转化反应(英文)

In reverse water gas shift (RWGS) reaction CO₂ is converted to CO which in turn can be used to produce beneficial chemicals such as methanol. In the present study, Mo/Al₂O₃, Fe/Al₂O₃ and Fe-Mo/Al₂O₃ catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, inductively coupled plasma atomic emission spectrometer (ICP-AES), temperature programmed reduction (H₂-TPR), CO chemisorption, energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) techniques. Kinetic properties of all catalysts were investigated in a batch reactor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/Al₂O₃ catalyst enhances its activity as compared to Fe/Al₂O₃. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/Al₂O₃ catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fe₂(MoO₄)₃ phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fe₂(MoO₄)₃ phase has low reducibility, therefore the Fe₂(MoO₄)₃ phase signifificantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al₂O₃ catalyst. Overall, this study introduces Fe-Mo/Al₂O₃ as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.     

Reduction of carbon dioxide with water under concentrated sunlight using photocatalyst combined with Fe-based catalyst

The reduction of CO₂ with water into valuable organic compounds under concentrated sunlight was investigated for the first time over a hybrid catalyst, in which a Pt-loaded K₂Ti₆O₁₃ photocatalyst was combined with a Fe-based catalyst supported on a dealuminated Y-type zeolite (Fe-Cu-K/DAY). In this reaction system, the Pt/K₂Ti₆O₁₃ catalyst decomposes water to produce H₂ and the Fe-Cu-K/DAY catalyst reduces CO₂ with the resulting H₂ into organic compounds. When only the Pt/K₂Ti₆O₁₃ photocatalyst was used, organic compounds such as CH₄, HCOOH, and HCHO were formed together with H₂, indicating that CO₂ can also be directly reduced over Pt/K₂Ti₆O₁₃. On the contrary, when the hybrid catalyst was used, CH₃OH and C₂H₅OH were produced in addition to the above products, depending on the reaction temperature and catalyst composition. The reaction temperature significantly increased by concentrating the solar irradiation, reaching 600 K and increasing the product yields. It is suggested that such a high reaction temperature facilitates both the photoreduction and hydrogenation of CO₂ over Pt/K₂Ti₆O₁₃ and Fe-Cu-K/DAY, respectively.     

纤维状BPO4/SiO2催化剂的制备及其丙烷氧化脱氢性能

通过静电纺丝法制备了一种高温焙烧后具有纤维状结构的磷酸硼/二氧化硅（BPO₄/SiO₂）催化剂,并考察了BPO₄负载量和焙烧温度对该催化剂的结构和催化丙烷氧化脱氢性能的影响。研究发现焙烧过程使纤维直径减小。随着BPO₄负载量的增加,丙烷氧化脱氢活性增高。当BPO₄负载量为7%（质量分数）,焙烧温度为600℃时,BPO₄/SiO₂催化剂具有最佳的催化性能;在反应温度为480℃下,丙烷转化率和丙烯产率分别达到17.0%和13.0%,且催化剂稳定性良好。当焙烧温度较低时（550℃）,催化剂中的有机物分子未被除尽,导致烯烃的选择性偏低;当焙烧温度较高时（700℃）,SiO₂结构收缩紧密,抑制了活性相的暴露。由于纤维结构可暴露更多活性位点,该催化剂较相同条件下粉末状BPO₄催化剂有着更高的催化活性。