Atom transfer carbonylation using ionic liquids as reaction media

Photo-induced ATC reactions of RI, CO, and amines to produce amides, were examined using ionic liquids, such as [bmim]PF₆ and [bmim]NTf₂, as reaction media in the presence of a catalytic amount of a Pd–carbene complex. When the primary alkyl iodide was used, the yield of the amide was lowered due to competing S_N2 reactions between RI and amines, whereas the reaction of the tertiary alkyl iodides was dependent on the structure of the substrates. ATC reactions of a wide variety of secondary RI proceeded smoothly when ionic liquids were used as reaction media. The Pd-catalyst and ionic liquid could also be recycled.     

Palladium-catalyzed Sonogashira cross-coupling of organic tellurides with alkynes

Alkyl aryl tellurides and a tellurol ester were used as coupling partners in Pd(0)-catalyzed Sonogashira reactions. Microwave-assisted reactions of alkyl aryl tellurides with alkynes in the presence of CuI and catalytic amounts of Pd(PPh₃)₄ produced alkynyl arenes. Similarly, a tellurol ester on reaction with alkynes afforded alkynyl phenyl ketones in the presence of CuI and a catalytic amount of Pd(PPh₃)₄ at room temperature.     

Composition Control Synthesis and Catalytic Properties in the Suzuki Reaction of Bimetallic PdSn Nanoparticles

We have successfully prepared 6.5 nm palladium tin (PdSn) alloy nanoparticles (NPs) with tunable compositions by high‐temperature reduction of tin acetate and palladium bromide in the presence of oleylamine and trioctylphosphine. The catalytic activities of PdSn NPs with different compositions were evaluated through Suzuki reactions. The PdSn nanocatalysts show better catalytic activity on Suzuki reactions than an equal amount of pure Pd NPs, and their catalytic activities are highly composition dependent. Among these NPs, Pd₆₃Sn₃₇/C NPs exhibited the highest catalytic performance with higher reaction activity, lower Pd leaching properties, and higher stability even after eight recycle reactions.     

Engineered mesoporous ionic‐modified γ‐Fe2O3@hydroxyapatite decorated with palladium nanoparticles and its catalytic properties in water

A new mesoporous organic–inorganic nanocomposite was formulated and then used as stabilizer and support for the preparation of palladium nanoparticles (Pd NPs). The properties and structure of Pd NPs immobilized on prepared 1,4‐diazabicyclo[2.2.2]octane (DABCO) chemically tagged on mesoporous γ‐Fe₂O₃@hydroxyapatite (ionic modified (IM)‐MHA) were investigated using various techniques. The synergistic effects of the combined properties of MHA, DABCO and Pd NPs, and catalytic activity of γ‐Fe₂O₃@hydroxyapatite‐DABCO‐Pd (IM‐MHA‐Pd) were investigated for the Heck cross‐coupling reaction in aqueous media. The appropriate surface area and pore size of mesoporous IM‐MHA nanocomposite can provide a favourable hard template for immobilization of Pd NPs. The loading level of Pd in the nanocatalyst was 0.51 mmol g^?1. DABCO bonded to the MHA surface acts as a Pd NP stabilizer and can also lead to colloidal stability of the nanocomposite in aqueous solution. The results reveal that IM‐MHA‐Pd is highly efficient for coupling reactions of a wide range of aryl halides with olefins under green conditions. The superparamagnetic nature of the nanocomposite means that the catalyst to be easily separated from solution through magnetic decantation, and the catalytic activity of the recycled IM‐MHA‐Pd showed almost no appreciable loss even after six consecutive runs.     

Efficient and ligand free palladium catalyst for Suzuki and Heck cross-coupling reactions

A simple and efficient system for Suzuki cross-coupling reactions was developed using a ligandless catalyst of Pd nanoclusters generated in situ from Pd(acac)₂. The cross-coupling reactions proceeded under mild reaction conditions with a high reaction rate (5 min) to give various biaryls in high yields. The system also exhibited catalytic potential for Heck reaction between aryl bromides and styrene.     

Benzimidazolyl based Schiff base palladium complex in an ionic liquid: an effective combination for Suzuki coupling

A new benzimidazole based Pd(II) Schiff base complex was prepared and its catalytic activity was evaluated for Suzuki cross-coupling reactions in ethyl-methyl imidazolium hexafluorophosphate [EMIM PF₆] ionic liquid at ambient temperature. The system provides a stable and reusable method for coupling reactions. Optimization for suitable reaction conditions were studied with respect to the effect of catalyst concentration, effects of additives, solvent and substituents on boronic acid. Good to excellent yields were achieved using a modest amount of the catalyst. The reaction time was less and the yield was more compared to previously reported results. In addition, the catalyst can be easily reused and recycled for six times without much loss in activity; this is an example of sustainable and green methodology.     

Hollow nanoshell-sphere Fe@Fe/Pd reactors: a magnetically recoverable catalyst for the C<Subscript>sp</Subscript>–S cross-coupling reactions in water

The hollow Pd–PVP–Fe nanosphere and Fe–PVP nanoparticle catalysts were synthesized by thermal method. Mixing of two metallic nanocatalysts was applied in the C_sp–S cross-coupling reactions between diphenyl disulfide and phenylacetylene under mild conditions in water. Results show that bi-catalytic system has higher catalytic efficiencies than their monocatalytic systems due to synergy between two catalysts. Order of adding two metallic catalysts were adjusted into the coupling reaction medium. Therefore, various bi-catalytic systems were obtained and characterized by XRD, SEM, EBSD, EDX, UV–Vis spectra, and particle size analyzer. Under special order of adding, the obtained hollow nanoshell-sphere Fe@Fe/Pd reactor showed higher catalytic activity in the coupling reaction compared to other bi-catalytic systems. The C_sp–S coupling products obtained of various diaryl disulfides and phenylacetylene at presence Fe@Fe/Pd (only 7.3?×?10^?5 mmol Pd) catalyst with moderate to high yields in water solvent and mild reaction conditions. After the reaction, the catalyst/product(s) separation could be easily achieved with an external magnet and more than 95% of catalyst could be recovered. The recovered catalyst was characterized by XRD, SEM, EBSD, EDX, and UV–Vis spectra. The Fe@Fe/Pd was reused at least six repeating cycles without any loss of its high catalytic activity. Tuning morphology and chemical composition of bi-catalytic system are key mainstays of high activity of Fe@Fe/Pd in repeating cycles of cross-coupling reactions.     

Rate and mechanism of the reaction of alkenes with aryl palladium complexes ligated by a bidentate P,P ligand in Heck reactions

The regioselectivity of the Heck reaction is supposed to be highly affected by the electronic properties of the alkene and the ionic or neutral character of the aryl palladium(II) complexes involved in the reaction with alkenes. In Heck reactions performed in dmf, [Pd(dppp){dppp(O)}Ph](+) (dppp=1,2-bis(diphenylphosphino)propane) is generated in the oxidative addition of PhI with [Pd(0)(dppp)(OAc)](-) formed in situ from Pd(OAc)(2) associated to two equivalents of dppp. [Pd(dppp){dppp(O)}Ph](+) is not very reactive with alkenes (styrene or methyl acrylate); however, it reacts with iodide ions (released in the catalytic reactions) to give [Pd(dppp)IPh] and with acetate ions (used as base) to give [Pd(dppp)(OAc)Ph]. [Pd(dppp)(OAc)Ph] reacts with styrene and methyl acrylate exclusively by an ionic mechanism, that is, via the cationic complex [Pd(dppp)(dmf)Ph](+) formed by dissociation of the acetate ion. The reaction of [Pd(dppp)IPh] is more complex and substrate dependent. It reacts with styrene exclusively by the ionic mechanism via [Pd(dppp)(dmf)Ph](+). [Pd(dppp)IPh] (neutral mechanism) and [Pd(dppp)(dmf)Ph](+) (ionic mechanism) react in parallel with methyl acrylate. [Pd(dppp)(dmf)Ph](+) is more reactive than [Pd(dppp)IPh] but is always generated at lower concentration.     

Support-Free Pd3Co NCs as an Efficient Heterogeneous Nanocatalyst for New Organic Transformations of C−C Coupling Reactions

A support-free heterogeneous Pd₃Co nanostructured composite (NC), synthesized through a hydrothermal route, acted as an effective catalytic system in multivariate Heck-, Sonogashira-, and Suzuki-type coupling reactions of iodonium ylides. The XPS analysis of the bimetallic Pd₃Co NCs confirmed the elemental composition as 75 % palladium and 25 % cobalt. Furthermore, high-resolution (HR) TEM analysis confirmed the spherical morphology of the Pd₃Co bimetallic nanoparticles. The average diameter of the NCs is 14.8 nm. The coupling reaction proceeded through the generation of α-iodoenones with simultaneous migration of the phenyl group, thereby giving a scaffold with higher atom economy. The heterogeneous Pd₃Co NCs were recycled and reused without any significant change in catalytic ability for up to five reaction cycles. The high concentration of Pd and association of cobalt into the lattice of palladium appears to enhance its catalytic ability for the diverse coupling reactions in comparison with its monometallic counterparts as well as with bimetallic NCs with a comparatively lesser amount of Pd.     

Synthesis of 1,5-disubstituted tetrazoles via Suzuki-Miyaura cross-coupling of 5-chloro-1-phenyltetrazole

Suzuki-Miyaura coupling reactions of 5-chloro-1-phenyl-tetrazole with various functionalized arylboronic acids were investigated. In the presence of catalytic amounts of SPhos/Pd(OAc)₂ or RuPhos/Pd(OAc)₂, the reaction proceeded smoothly to afford 1,5-diaryltetrazoles in good to excellent yields.     

SBA-15负载Pd催化剂的制备及其在Heck反应中的应用研究

利用水热反应制备了表面离子液体功能化的SBA-15介孔材料,在丙酮溶液中与氯化钯反应,然后使用水合肼在乙醇中还原.测试了这种催化剂在Mizoroki-Heck反应中的催化活性.与直接负载在SBA-15上的钯催化剂相比,这种表面修饰的介孔SBA-15负载催化剂表现出更高的催化活性、可回收性和反应稳定性.氮气吸脱附实验和小角XRD衍射实验表明,在合成中,材料的介孔性能并没有被破坏.透视电镜也表征了该材料的表面形貌.最后,Mizoroki-Heck反应表明该催化剂具有很高的催化活性,且循环五次后,其催化活性降低并不明显.     

Kinetic Limitations in Catalytic Reactions

A universal equation imposing limitations on the kinetics of catalytic reactions was obtained. The equation was shown to be valid for the 2CO + O₂ → 2CO₂ reaction on the Pd(111) surface and several other reactions.     

A facile synthesis of 3-allyl-4-hydrazinocyclopentenes by the palladium/Lewis acid mediated ring opening of bicyclic hydrazines with allyltributyltin and allyltrimethylsilane

A facile method for the synthesis of 3-allyl-4-hydrazinocyclopentenes from bicyclic hydrazines by the Pd/Lewis acid catalyzed reaction of allyltributyltin and allyltrimethylsilane is described. The role of ionic liquid [bmim]PF₆ as a solvent as well as a promoter is also demonstrated by carrying out the reactions in ionic liquid without Lewis acid.     

A PdCl2–ionic liquid brush assembly: an efficient and reusable catalyst for Mizoroki–Heck reaction in neat water

An efficient and reusable heterogeneous catalytic assembly of PdCl₂ held in ionic liquid brushes has been synthesized and an environmentally‐friendly procedure was developed for coupling aryl iodides with acrylic acid. These reactions were conducted in water under aerobic conditions with water‐insoluble or even solid aryl iodides and they proceeded smoothly and cleanly without any organic co‐solvent or other additives. A 0.5 mol% (based on Pd atom) dose of the catalyst was found to be sufficient for Mizoroki–Heck reaction. The catalyst is easily recovered post reaction, via simple filtration, and reused at least eight times without a noticeable loss of activity. The protocol has the advantages of excellent yield, environmental friendliness, and catalyst recyclability. Copyright © 2011 John Wiley & Sons, Ltd.     

The Origin of Shape Sensitivity in Palladium‐Catalyzed Suzuki–Miyaura Cross Coupling Reactions

The shape sensitivity of Pd catalysts in Suzuki–Miyaura coupling reactions is studied using nanocrystals enclosed by well‐defined surface facets. The catalytic performance of Pd nanocrystals with cubic, cuboctahedral and octahedral morphologies are compared. Superior catalytic reactivity is observed for Pd NCs with {100} surface facets compared to {111} facets. The origin of the enhanced reactivity associated with a cubic morphology is related to the leaching susceptibility of the nanocrystals. Molecular oxygen plays a key role in facilitating the leaching of Pd atoms from the surface of the nanocrystals. The interaction of O₂ with Pd is itself facet‐dependent, which in turn gives rise to more efficient leaching from {100} facets, compared to {111} facets under the reaction conditions.     

Pd‐Cu alloy nanoparticle supported on amine‐terminated ionic liquid functional 3D graphene and its application on Suzuki cross‐coupling reaction

Well distributed Pd‐Cu bimetallic alloy nanoparticles supported on amine‐terminated ionic liquid functional three‐dimensional graphene (3D IL‐rGO/Pd‐Cu) as an efficient catalyst for Suzuki cross‐coupling reaction has been prepared via a facile synthetic method. The introduction of IL‐NH₂ cations on the surface of graphene sheets can effectively avoid the re‐deposition of graphene sheets, allowing the catalyst to be reused up to 10 cycles. The addition of Cu not only saves cost but also ensures high catalytic efficiency. It is worthy to note that the catalyst 3D IL‐rGO/Pd_2.5Cu_2.5 can efficiently catalyze the Suzuki cross‐coupling reaction with the yield up to 100% in 0.25 h, almost one‐fold higher than that by the pristine IL‐rGO/Pd_2.5 catalyst (52%). The Powder X‐Ray Diffraction (XRD), combining energy dispersive X‐ray spectroscopy (EDS) mapping results confirm the existence and distribution of Pd and Cu in the bimetallic nanoparticles. The transmission electron microscopy (TEM) reveals the nanoparticle size with an average diameter of 3.0 ± 0.5 nm. X‐ray photoelectron spectroscopy (XPS) analysis proved the presence of electron transfer from Cu to Pd upon alloying. Such alloying‐induced electronic modification of Pd‐Cu alloy and 3D ionic liquid functional graphene with large specific surface area both accounted for the catalytic enhancement.     

Diphenylphosphinite ionic liquid (IL-OPPh2): A solvent and ligand for palladium-catalyzed silylation and dehalogenation reaction of aryl halides with triethylsilane

The use of an imidazolium-based phosphinite ionic liquid (IL-OPPh₂) as both solvent and ligand for Pd offers an efficient catalytic system for silylation of aryl iodides, bromides and also chlorides by triethylsilane in the presence of Cs₂CO₃. In the absence of base, this system is also performed for catalytic dehalogenation of aryl halides. The ionic liquid containing its corresponding Pd(0) complex can be easily recovered and reused in several runs without losing its efficiency.     

Palladium–cadmium sulfide nanopowder at oil–water interface as an effective catalyst for Suzuki–Miyaura reactions

A simple and effective strategy is described for the synthesis of Pd–CdS nanopowder by the reduction of an organopalladium(II) complex, [PdCl₂(cod)] (cod = cis ,cis ‐1,5‐cyclooctadiene), in the presence of CdS quantum dots (QDs) at a toluene–water interface. We investigated the impact of addition of CdS QDs on catalytic activity of Pd nanoparticles (NPs). The Pd–CdS nanopowder functions as an efficient catalyst for Suzuki–Miyaura reactions for the formation of carbon–carbon bonds. There is a high electron density on Pd NPs and due to their high electron affinity they behave as an electron scavenger from CdS increasing the rate of oxidative addition, which is the rate‐determining step of the catalytic cycle, and, just as we expect, the C─C coupling reaction with the Pd–CdS nanopowder is faster and occurs in less time than that with Pd nanocatalysts. Compared to classical reactions, this method consistently has the advantages of short reaction times, high yields in a green solvent, reusability of the catalyst without considerable loss of catalytic activity and low cost, and is a facile method for the preparation of the catalyst.     

Vapor Phase Carbonylation Reactions Using Methyl Nitrite Over Pd Catalysts

Vapor phase carbonylation reactions using methyl nitrite (MN) as an oxidant have been developed by Ube Industries, Ltd. Dimethyl oxalate (DMO) and dimethyl carbonate (DMC) are synthesized efficiently over Pd(0) and Pd(II) catalysts under mild condition in gas phase, respectively. In these synthesis procedures, two kinds of separate reactions are involved. The first reaction is the catalytic synthesis of DMO or DMC from MN and CO; and the second reaction is non-catalytic MN synthesis from methanol, O₂ and NO, which is produced from the first reaction. The high DMO or DMC selectivity and suppression of catalyst deactivation originate from the facts that O₂ is not involved and H₂O is not produced in the first reaction.     

Synthesis of Enaminone‐Pd(II) Complexes and Their Application in Catalysing Aqueous Suzuki‐Miyaura Cross Coupling Reaction

A series of Pd(II)‐enaminone complexes, termed Pd(eao)₂, have been synthesized and characterized. The investigation on the catalytic activities of these new Pd(II)‐reagents has proved that the Pd(eao)₂‐ 1 possesses excellent catalytic activity for the Suzuki‐ Miyaura cross coupling reactions of aryl bromides/chlorides with aryl/vinyl boronic acids in the environmentally benign media of aqueous PEG400 at low loading (5 mol‰). The superiority of this Pd(II)‐reagent to those commercial Pd(II) and Pd(0) catalysts in catalyzing the reactions has been confirmed by parallel experiments. What's more, Pd(eao)₂‐ 2 has been found as a practical catalyst for the homo‐coupling reactions of aryl boronic acids.