- Kinetically controlled synthesis of triangular and hexagonal nanoplates of palladium and their SPR/SERS properties
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The rapid reduction of Na2PdCl4 by ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP) has recently been demonstrated as a convenient method of generating Pd cubooctahedra and twinned nanoparticles. Here we describe a new procedure where Pd triangular or hexagonal nanoplates could be selectively synthesized by manipulating the reduction kinetics of the polyol process. More specifically, the reduction rate was substantially reduced through the introduction of Fe(III) species and the O2/Cl- pair, two wet etchants for Pd(0). The etching power of the O 2/Cl- pair could be further enhanced by adding an acid to lower the pH of the reaction solution. Unlike the previously reported synthesis of Ag and Au nanoplates, light was found to have no indispensable role in the formation of Pd nanoplates. Both triangular and hexagonal nanoplates of Pd exhibited surface plasmon resonance (SPR) peaks in the visible region, and their positions matched with the results of discrete dipole approximation (DDA) calculation. Thanks to their sharp corners and edges, these Pd nanoplates could serve as active substrates for surface-enhanced Raman scattering (SERS).
- Xiong, Yujie,McLellan, Joseph M.,Chen, Jingyi,Yin, Yadong,Li, Zhi-Yuan,Xia, Younan
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- Characterisation and microstructure of Pd and bimetallic Pd-Pt catalysts during methane oxidation
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The catalytic oxidation of methane was studied over Pd/Al2O3 and Pd-Pt/Al2O3. It was found that the activity of Pd/Al2O3 gradually decreases with time at temperatures well below that of PdO decomposition. The opposite was observed for Pd-Pt/Al2O3, of which the activity decreases slightly with time. Morphological studies of the two catalysts showed major changes during operation. The palladium particles in Pd/Al2O3 are initially composed of smaller, randomly oriented crystals of both PdO and Pd. In oxidising atmospheres, the crystals become more oxidised and form larger crystals. The activity increase of Pd-Pt/Al2O3 is probably related to more PdO being formed during operation. The particles in Pd-Pt/Al2O3 are split into two different domains: one with PdO and the other likely consisting of an alloy between Pd and Pt. The alloy is initially rich in palladium, but the composition changes to a more equalmolar Pd-Pt structure during operation. The ejected Pd is oxidised into PdO, which is more active than its metallic phase. The amount of PdO formed depends on the oxidation time and temperature.
- Persson, Katarina,Jansson, Kjell,Jaeras, Sven G.
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- Transformations of β-hydroxo-substituted η3-allyl Pd complexes in neutral and weakly acidic solutions
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The oxidation of some β-hydroxo-substituted η3-allyl Pd complexes based on the simplest 1,3-dienes is studied by the 1H and 13C NMR methods in neutral and weakly acidic methods. The composition of the reaction products is
- Finashina,Kramareva,Evstigneeva,Flid,Belov
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- Cross-coupling versus homocoupling in the reactions of dimethyl(N,N,N′,N′-tetramethylethanediamine)palladium with organic halides
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Reaction of PdMe2(tmeda) (tmeda = N,N,N′,N′-tetramethylethanediamine) with benzyl and allyl bromide at 20°C affords the homocoupled product ethane and the organometallic complexes PdBr(η1-benzyl)(tmeda) and [Pd(η3-allyl)(tmeda)]Br, respectively. The reaction of PdMe2(tmeda) with acetyl chloride did not give the acetyl complex PdCl(COMe)(tmeda). Instead, the cross-coupled product acetone and the organometallic product PdClMe(tmeda) were obtained. Acetyl complexes PdX(COMe) (tmeda) were easily obtained by reaction of PdXMe(tmeda) with carbon monoxide at ambient temperature and pressure. The reaction of PdMe2(tmeda) with ethyl iodide is not selective and gives a 3:2 mixture of PdIMe(tmeda) and PdIEt(tmeda) together with a 3:2 mixture of propane and ethane. At 0°C, the reaction of PdMe2(tmeda) with benzyl bromide and the reaction of PdMe(benzyl)(tmeda) with methyl bromide both afford the palladium(IV) species a-benzyl-b-bromo-cd-dimethyl-ef-(tmeda)palladium(IV) (4a), in which the benzyl group and the bromine atom are in a cis position. 1H NMR spectroscopy in acetone-d6 at 0°C shows that in the reaction of the platinum(IV) complex PtMe2(tmeda) with benzyl bromide a trans oxidative-addition product, a-benzyl-f-bromo-bc-dimethyl-de-(tmeda)platinum(IV) (8a), is formed initially and that this complex rapidly isomerizes to a-benzyl-b-bromo-cd-dimethyl-ef-(tmeda)platinum(IV) (8b). We believe that similar addition/isomerization sequences occur in the reactions leading to 4a. The configuration of the thermodynamically stable palladium(IV) and platinum(IV) cis oxidative-addition products (4a and 8b) seems to be controlled by steric interaction between the benzyl group and the tmeda ligand.
- De Graaf, Wim,Boersma, Jaap,Van Koten, Gerard
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- Energetic and entropic contributions to self-assembly of binary nanocrystal superlattices: Temperature as the structure-directing factor
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We studied the effect of temperature on self-assembly of monodisperse colloidal nanocrystals into single-component and binary superlattices. Temperature, which serves as a weighting factor for the internal energy (U) and entropy (S) contributions to the Helmholtz free energy F = U - TS, allows tailoring relative weights of the interparticle interactions and free-volume entropy during the formation of nanocrystal superlattices. Temperature also provides a convenient tool for directing self-assembly of nanocrystals toward desired superlattice structures. We found that temperature strongly affects the structures of binary superlattices self-assembled from the mixtures of CdSe + PbS nanocrystals and PbSe + Pd nanocrystals. In the former case, small Hamaker constants for CdSe and PbS nanocrystals led to a relatively simple phase diagram, including only high-density NaZn13-, AlB2-, and NaCl-type binary superlattices. In contrast, binary superlattices self-assembled at different temperatures from PbSe and Pd nanocrystals showed a number of low-density complex phases stabilized by strong local van der Waals interactions between Pd nanocrystals. The structural diversity of nanoparticle superlattices is shown to be a result of the cooperative effect of the entropy-driven crystallization and the interparticle interactions. Both ΔU and TΔS terms associated with the superlattice formation should be of the same order of magnitude, with |ΔU| |TΔS| for the PbSe and Pd nanocrystals.
- Bodnarchuk, Maryna I.,Kovalenko, Maksym V.,Heiss, Wolfgang,Talapin, Dmitri V.
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- Formation of palladium nanoparticles in olefin oxidation with iron(III) aqua ions in the presence of the Pd/ZrO2/SO4 metallic catalyst
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The reactions of the Pd/ZrO2/SO4-catalyzed oxidation of ethylene, propene, and but-1-ene in a 0.1-1.5 M solution of perchloric acid with iron(III) aqua ions to carbonyl compounds, viz., acetaldehyde, acetone, and methyl ethyl ketone, respectively, were studied. The formation of palladium nanoparticles (5 nm) in solution on contact of the initial heterogeneous Pd/ZrO2/SO4 catalyst with perchloric acid was proved by transmission electron microscopy. The palladium nanoparticles are assumed to play the key role in olefin oxidation with the iron(III) aqua ions.
- Potekhin,Matsura
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- Recovery of palladium from spent solutions for manufacture of catalysts
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Palladium recovery from [Pd(NH3)4]Cl2 solutions (concentration in terms of the metal 1 g l-1) with flow-through porous electrodes was studied. The conditions of effective electrochemical recovery of Pd were found. Various porous cathodes were compared.
- Belobaba,Maslii,Medvedev
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- Hydrogen sorption in Pd monolayers in alkaline solution
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Hydrogen adsorption/absorption at palladium monolayers (ML) deposited on monocrystalline Au(1 1 1) electrode was studied in 0.1 M NaOH solution. H charge isotherms demonstrated that adsorption started at potentials more positive than at thicker nanometric
- Martin,Lasia
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- Mechanism of the reaction between the aqua complexes of palladium(II) and iron(II) in a solution of HClO4
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The kinetics of the reaction of an aqua complex of iron(II) with a tetraaqua complex of palladium(II) in a perchloric acid solution was studied over the temperature range 2055°C, and a reaction mechanism was proposed. It was found that the reaction is autocatalytic, and it occurs by a two-step one-electron transfer mechanism with the formation of iron(III) and palladium black. Based on the kinetic data, the nature of the autocatalysis in the test reaction was hypothesized.
- Potekhin,Matsura,Solov'eva,Potekhin
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- Electroless Deposition of Palladium at Bare and Templated Liquid/Liquid Interfaces
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A simple, electroless approach to metallize the liquid/liquid interface is reported. The method is illustrated with the deposition of Pd at the bare water/1,2-dichloroethane interface, and for the templated deposition of Pd within the 100 nm diameter pores of γ-alumina membranes. Copyright
- Dryfe, Robert A. W.,Simm, Andrew O.,Kralj, Brett
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- A novel electrochemical sensor for formaldehyde based on palladium nanowire arrays electrode in alkaline media
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A novel electrochemical sensor for the detection of formaldehyde based on palladium (Pd) nanowire (NW) arrays was developed. The Pd NW arrays were obtained via the direct electrodeposition of Pd on a glassy carbon electrode within the pores of an anodized aluminum oxide membrane. The electrocatalytic activity of the Pd NW arrays electrode for formaldehyde detection in alkaline media was then investigated via a series of electrochemical measurements; the results show the very high catalytic activity of the electrode. The formaldehyde oxidation on the Pd NW arrays electrode at +0.03 V, which is more negative than that in previous report. The experimental data further reveal that the electrooxidation of formaldehyde inhibits the formation of the poisonous intermediate, carbon monoxide. The proposed sensor has high sensitivity and fast response to formaldehyde, and the oxidation current has a linear relationship with the formaldehyde concentration in the 2 μM to 1 mM range (R = 0.9982). The detection limit was 0.5 μM (S/N = 3). The sensor has high sensitivity and good selectivity.
- Zhang, Yan,Zhang, Min,Cai, Zhiquan,Chen, Meiqiong,Cheng, Faliang
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- Magnetic properties of transition-metal nanoclusters on a biological substrate
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We have investigated the magnetic properties of transition-metal clusters with a single grain size of about 1 nm. These metallic nanoclusters have been deposed on a biological substrate. This substrate is a purified self-assembling paracrystalline surface layer (S-layer) of the Bacillus sphaericus strain JG-A12, which exhibits square symmetry and is composed of identical protein monomers. First data of the magnetic susceptibility, taken in a SQUID magnetometer at 0a crucial role for the occurrence of superconductivity in microgranular Pt by adjusting the balance between electron-phonon interactions and competing magnetic interactions.
- Herrmannsd?erfer,Bianchi,Papageorgiou,Pobell,Wosnitza,Pollmann,Merroun,Raff,Selenska-Pobell
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- Spontaneous deposition of Pd on a Ru(0 0 0 1) surface
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Spontaneous deposition of Pd on a Ru(0 0 0 1) single crystal surface has been demonstrated by an in situ scanning tunneling microscopy technique. The immersion of an ultrahigh vacuum prepared Ru single crystal in a palladium ion containing solution results in a formation of an epitaxial and textured multilayer Pd deposit without applying an external potential. The amount of deposited Pd can be indirectly controlled by the amount of Pd ions confined in the solution volume in contact with a Ru surface. The results suggest that the initial Pd growth involves formation of an ordered monolayer, while further growth results in formation of a three-dimensional Pd deposit.
- Brankovic,McBreen,Ad?í
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- Synthesis and some properties of Heteronuclear platinum and palladium carbonyl clusters
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Heteronuclear clusters of general formula [PtxPd y(CO)z] were synthesized by reaction of CO with PtCl 4 + PdCl2 solutions in 95% ethanol at room temperature and atmospheric pressure. The products isol
- Fedoseev,Gerasimova,Loginova
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- One-step synthesis of metallic and metal oxide nanoparticles using amino-PEG oligomers as multi-purpose ligands: Size and shape control, and quasi-universal solvent dispersibility
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A one-step and room temperature synthesis toward metallic and metal oxide nanoparticles soluble both in water and organic solvent is reported. This was achieved using amino-PEG oligomers that make it possible to control the size and shape of the nanoparticles.
- Rubio-Garcia, Javier,Coppel, Yannick,Lecante, Pierre,Mingotaud, Christophe,Chaudret, Bruno,Gauffre, Fabienne,Kahn, Myrtil L.
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- Self-organization of spherical, core-shell palladium aggregates by laser-induced and thermal decomposition of [Pd(PPh3)4]
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(Figure Presented) Metal in the middle: Uniform, spherical, core-shell aggregates (100 ± 20 nm; see picture) are obtained by photodecomposition of [Pd(PPh3)4] to form the metal core, followed by aggregation of smaller Pd nanocrystals
- Ye, Enyi,Tan, Hua,Li, Shuping,Fan, Wai Yip
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- Factors influencing linkage isomer preference in palladium(II)-chloranilate complexes
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The actors inluencing linakge isomer preference in the bonding between palladium(II) and the chloranilate dianion (CA2-) are addressed through the synthesis and specctroscopic characterization of 16 compounds where L2 = 2C
- Jeong, Woo-Yeong,Holwerda, Robert A.
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- Synthesis of bimetallic PdAu nanoparticles for formic acid oxidation
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In this work, a simple co-deposition strategy for the synthesis of carbon-supported Pd-Au alloy was reported. Our approach involves the co-reduction of Au and Pd ions using ethylene glycol and sodium citrate as the reducing and stabilizing reagents. Both alloy and non-alloy bimetallic Pd-Au nanoparticles are produced using a right rate-limiting strategy. For example, when ethylene glycol and sodium citrate are the limiting reagent with Au and Pd ions in excess, the synthesis environment favors preferential nucleation and growth of Au nanoparticles followed by deposition of Pd either as the shell of Au core or as separate Pd clusters. On the other hand, if the supply of metal ions (not the reducing reagents) limits the reaction, it creates a synthesis condition for Pd-Au alloy particles. The as-prepared Pd-Au alloys exhibit higher Pd-specific activities towards formic acid oxidation compared with the non-alloy counterpart or individual Pd catalyst and an easier removal of adsorbed oxygen species (e.g., Oads or OHads) was observed from the surface of Pd-Au alloy with a higher content of Au.
- Suo, Yange,Hsing, I-Ming
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- Synthesis of nearly monodisperse palladium (Pd) nanoparticles by using oleylamine and trioctylphosphine mixed ligands
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In this paper, we report a facile method to prepare nearly monodisperse Pd nanoparticles by heating Pd(II) ions in 4-tert-butyltoluene solvent, in the presence of oleylamine and trioctylphosphine (TOP) ligands. It has been found the concentration of TOP l
- Yang, Zhiqiang,Klabunde, Kenneth J.
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- Fabrication of high aspect ratio ferroelectric microtubes by vacuum infiltration using macroporous silicon templates
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Ordered arrays of high aspect ratio (>10:1) ferroelectric Pb(Zr 0.52Ti0.48)O3 (PZT) tube structures were fabricated by vacuum infiltration of macroporous silicon (Si) templates. Improved phase purity was achieved when PZT microtubes were pyrolyzed at 300°C and partially released from the Si template to prevent a chemical reaction between the Pb and the Si during subsequent high-temperature crystallization. The free-standing microtubes were crystallized by rapid thermal annealing at 750°C for 1-3 min. Perovskite phase formation was confirmed by X-ray diffraction and transmission electron microscopy methods. Coaxial structures comprised of metallic LaNiO3, PZT, and Pd layers were also processed to enable future electrical characterization of the ferroelectric microtubes.
- Bharadwaja,Olszta,Trolier-McKinstry,Li,Mayer,Roozeboom
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- Catalytically active nano-porous cobalt-palladium alloys
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The potential advantages of nano-alloys and particularly, nano-porous alloys, place them at the “spotlight” of heterogeneous catalysis. Nevertheless, controlling the precise compositions of these materials is still a synthetic challenge. Previous research introduced the fabrication of metals and alloys with a high nano-scale porosity and controllable compositions, via a hydrogen-mediated chemical reduction process of metal complex salts. We have used this procedure to obtain two magnetic nano-porous Co-Pd alloys, pure porous palladium and pure porous cobalt. Single crystal X-ray diffraction studies enabled structural determination of the two Co-Pd bi-complex salts that were used as precursors for these alloys. Powder X-ray diffraction studies determined the crystalline phases of the alloys and indicated the nanometric size of their crystallites. High-resolution scanning electron microscopy indicated that these alloys assemble as highly porous clusters of interconnected nano-crystallites. It also indicated that each alloy cluster preserves the micrometric morphologies of its salt precursor. Energy dispersive X-ray spectroscopy showed that the alloys exhibit uniform composition down to the micro-level, which preserved the Co/Pd ratio within the salts. Focused ion beam tomography enabled 3D structural representation of the alloys and metals. Geometrical analysis of the 3D reconstructed data determined 90% porosity and a specific surface area of ~100 m2/g for the alloys. In addition, the alloys showed improved catalytic activity in the semi-hydrogenation of phenylacetylene, compared to the pure metals and commercial Pd/C. Moreover, their magnetic properties enabled facile recovery at the end of the reaction. The yield for styrene in this reaction was increased using “design of experiments” (DOE), a method for optimization of reaction conditions. Furthermore, our experiments implied that a highly porous structure significantly improves the selectivity of styrene in the reaction. These results demonstrated the advantage of fabricating nano-porous alloys with uniform compositions that may exhibit special properties and serve as new and efficient catalysts.
- Avisar, Shay,Shner, Yahel,Abu-Reziq, Raed,Popov, Inna,Bino, Avi
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- Thermal decomposition of palladium(ii) pyrazolyl complexes: Part II
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Thermal behavior of pyrazolyl complexes [PdCl2(HPz)2] (1), [PdCl2(HdmPz)2] (2), [Pd(SCN)2(HPz) 2] (3), [Pd(SCN)2(HdmPz)2] (4), [Pd(N 3)2(HdmPz)s
- Netto,Santana,Mauro,Frem, Regina C. G.,De Almeida,Crespi, Marisa S.,Zorel Jr.
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- Synthesis of Cu-Pd alloy thin films by co-electrodeposition
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This paper presents results on the synthesis of Cu-Pd alloy thin films on Ti substrates by co-electrodeposition of Pd and Cu from nitrate-base electrolytic baths. The deposition rates of Cu and Pd were determined by Electrochemical Quartz Crystal Microbalance as a function of the electrode potential and Cu+2 and Pd+2 concentrations. It is shown that electrodeposition of copper and palladium occurs simultaneously at -0.50 V vs. SCE and that Cu-Pd thin films over the entire composition range were obtained by changing the composition of the solution. X-ray diffraction analyses indicated that these films have a nanocrystalline single-phase face-centered cubic structure and scanning electron microscopy analyses showed that potentiostatically deposited films are rough and porous, which is appropriate for electrocatalysis applications. In an attempt to get denser deposits as required for H2 purification applications, pulsed potential co-electrodeposition was performed and the effect of the deposition conditions on the roughness of the films was assessed by double layer capacitance measurements. It was shown that smooth Cu-Pd films (with Rf value as low as 8, as opposed to more than 120 for films prepared in the potentiostatic mode) could be obtained with a proper choice on the deposition conditions.
- Allemand, Morgan,Martin, Manuel. H.,Reyter, David,Roue, Lionel,Guay, Daniel,Andrei, Carmen,Botton, Gianluigi A.
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- Regulating peroxidase-like activity of Pd nanocubes through surface inactivation and its application for sulfide detection
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A new analytical method is described for the colorimetric detection of sulfide. This approach involves the use of Pd nanocubes (PdNCs) as artificial peroxidases that can effectively generate a colored signal by catalyzing the oxidation of peroxidase substrates. In the presence of sulfide, the colored signal is greatly diminished because of the specific and efficient inhibition of the peroxidase-like activity of the PdNCs through their surface inactivation by the formation of PdS. Based on this finding, sulfide assay can be achieved in the 0.125-2.75 μM concentration range with a detection limit of 80 nM. This method shows high selectivity to sulfide besides other ions, and has been applied for the determination of sulfide in spiked real samples. It also features simplicity and rapidness since the assay can be conducted at room temperature, in aqueous solution, and requires only ~5 min.
- Wang, Yi,Zhang, Pu,Liu, Lei,Xue, Fei,Liu, Maochang,Li, Ling,Fu, Wensheng
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- Synthesis, characterization, and biological activity of a new palladium(II) complex with deoxyalliin
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Synthesis, characterization, and biological activity of a new water-soluble Pd(II)-deoxyalliin (S-allyl-L-cysteine) complex are described in this article. Elemental and thermal analysis for the complex are consistent with the formula [Pd(C6H10NO2S)2]. 13C NMR, 1H NMR, and IR spectroscopy show coordination of the ligand to Pd(II) through S and N atoms in a square planar geometry. Final residue of the thermal treatment was identified as a mixture of PdO and metallic Pd. Antiproliferative assays using aqueous solutions of the complex against HeLa and TM5 tumor cells showed a pronounced activity of the complex even at low concentrations. After incubation for 24 h, the complex induced cytotoxic effect over HeLa cells when used at concentrations higher than 0.40 mmol/L. At lower concentrations, the complex was nontoxic, indicating its action is probably due to cell cycle arrest, rather than cell death. In agreement with these results, the flow cytometric analysis indicated that after incubation for 24 h at low concentrations of the complex cells are arrested in G0/G1.
- Corbi, Pedro P.,Massabni, Antonio C.,Moreira, Andreia G.,Medrano, Francisco J.,Jasiulionis, Miriam G.,Costa-Neto, Claudio M.
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- Cascade approach for synthesis of R-1-phenyl ethyl acetate from acetophenone: Effect of support
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One-pot synthesis of R-1-phenylethyl acetate starting from acetophenone hydrogenation was studied over supported palladium catalysts in combination with an immobilized lipase. Ethyl acetate was used as an acyl donor and the experiments were carried out under 1 bar hydrogen at 70 °C. In this work, the effect of support acidity was systematically investigated by using two mesoporous Pd-H-MCM-41 and Pd-Si-MCM-41 catalysts as hydrogenation catalysts. Furthermore their performance was compared with the performances of Pd-SiO2 and Pd-Al2O3. The catalysts acidity was determined by pyridine adsorption while the metal crystallite sizes were measured by XRD technique. The initial hydrogenation rates of acetophonene decreased with increasing Pd crystallite sizes. Initially both R- and S-1-phenylethanol were formed with the same rates. After prolonged reaction times activities of both hydrogenation catalyst and lipase declined. The former catalyst deactivated due to formation of acetic acid via deacylation reaction, whereas ethanol formed as a stoichiometric product in acylation decreased the lipase activity. The formation of ethylbenzene via dehydration of an intermediate alcohol, (R,S)-1-phenylethanol was enhanced by acidic catalysts. The most selective catalyst for one-pot synthesis of R-1-phenylethylacetate was a slightly acidic Pd-Al2O3 in combination with lipase. A reaction network was proposed based on the kinetic data.
- M?ki-Arvela, P?ivi,Sahin, Serap,Kumar, Narendra,Heikkil?, Teemu,Lehto, Vesa-Pekka,Salmi, Tapio,Murzin, Dmitry Yu.
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- A palladium(II) complex with a chelating (carboxy) phosphanoalkyl ligand
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rac-[SP-4-2]-{2-[(dimethylamino-κN)methyl]phenyl-κC 1}{[2-(diphenylphosphanyl-κP)ferrocenyl](methoxycarbonyl) methyl-κC}palladium(II) (1) was synthesized by deprotonation of [SP-4-4]-chloro{2-[(dimethylamino-κN)methyl]phenyl-κC 1}{rac-methyl 2-(diphenylphosphanyl)ferrocenylacetate-κP} palladium(II) with t-BuOK. Complex 1 was characterized by spectral methods and its reactivity studied. The structure of 1 was determined by X-ray crystallography and discussed in relation to other complexes with phosphanoalkyl ligands derived from phosphanoacetic esters.
- ?těpni?ka, Petr
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- Catalytic activity of electrolytic palladium deposits on porous nickel substrates
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Catalytic activity of palladium layers in reduction of atmospheric oxygen and oxidation of methanol and ethanol in an alkaline medium was studied for electrolytic palladium deposits on porous nickel substrates by cyclic voltammetry on a rotating disk electrode. Pleiades Publishing, Ltd., 2011.
- Nikiforova,Savel'Eva,Datskevich
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- Surface-enhanced Raman scattering of 4-mercaptopyridine on thin films of nanoscale Pd cubes, boxes, and cages
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We have synthesized a variety of Pd nanoparticles of 8-50 nm in size including solid cubes, hollow boxes, and porous cages. Using 4-mercaptopyridine (4MP) as a probe molecule, we have characterized thin films for surface-enhanced Raman scattering (SERS) activity, and have found a significant level of enhancement (with factors ranging from 170 for 8-nm cubes to 1.3 × 104 for boxes). For the cubes and boxes, we observed a trend of stronger enhancement with more red-shifted SPR bands. We evaluated the sensitivity of this approach, and also used SERS to monitor monolayer formation on these particles.
- McLellan, Joseph M.,Xiong, Yujie,Hu, Min,Xia, Younan
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- Thermal and spectroscopic investigation on N,N-dimethylbenzylamine based cyclopalladated compounds containing isonicotinamide
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Synthesis, spectroscopic characterization and thermal analysis of the [Pd(dmba)(Cl)(iso)] (1), [Pd(dmba)(NCO)(iso)] (2), [Pd(dmba)(N 3)(iso)] (3) and [Pd(dmba)(Br)(iso)] (4) (dmba = N,N′- dimethylbenzylamine; iso = isonicotinamide) compounds ar
- Stevanato, Alessandra,Mauro, Antonio E.,Netto, Adelino V. G.
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- Are organotin reagents derived from bis(trimethylsilyl)picoline suitable precursors for the preparation of cyclometallated complexes?
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The organotin reagents [2-PyC(SiMe3)2SnR3] (R = Me, nBu) were prepared in good yields from the reaction between the lithium salt of 2-bis(trimethylsilyl)picoline and the corresponding trialkyltin chlorides. Reac
- Molter, Anja,Mohr, Fabian
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- Combined redox couples for catalytic oxidation of methane by dioxygen at low temperatures
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The combination of three redox couples Pd2+/Pd0-quinone/hydroquinone-NO2/NO creates an electron-transfer loop, which facilitates one-pot catalytic oxidation of methane selectively to methanol by dioxygen in CF3COOH at a temperature as low as 80 °C. This is the first example where an organic cocatalyst significantly increases the catalytic efficiency of a transition metal in the selective oxidation of methane in the presence of dioxygen. Copyright
- An, Zengjian,Pan, Xiulian,Liu, Xiumei,Han, Xiuwen,Bao, Xinhe
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- CRYSTALLIZATION OF METALLIC GLASS Pd80Si20.
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The crystallization behavior was studied by means of in situ observation during heating in a TEM. The crystallization process can be divided into four stages: ordering of atoms in the amorphous matrix, the initial stage of crystallization in which some metastable phases appear at local regions, rapid crystallization by a eutectic reaction, and metastable phases transformation to a stable phase. The structures of these metastable phases are analysed by electron diffraction.
- Li,He
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- SERS at structured palladium and platinum surfaces
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Palladium and platinum are important catalytic metals, and it would be highly advantageous to be able to use surface enhanced Raman spectroscopy (SERS) to study reactive species and intermediates on their surfaces. In this paper we describe the use of tem
- Abdelsalam, Mamdouh E.,Mahajan, Sumeet,Bartlett, Philip N.,Baumberg, Jeremy J.,Rusell, Andrea E.
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- Palladium metal and palladium oxide particle production by spray pyrolysis
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Spray pyrolysis was used to produce dense, spherical palladium metal particles at and above 900 °C in air and 800 °C in nitrogen, well below the melting point of palladium (1554 °C). Palladium oxide particles were produced at lower temperatures. At 500 °C the PdO particles were composed of nanocrystalline grains 5 to 15 nm in diameter and had surface areas of 30.2 to 32.8 m2/g. The particles became less porous and less polycrystalline as temperature increased. At 800 °C the PdO particles were polycrystalline with grains of 20 to 50 nm and a surface area of 3.23 m2/g. The Pd particles produced at 900 °C by decomposition of the oxide were single-crystalline and fully-dense. These observations are consistent with the formation of porous but not hollow aggregates of PdO at lower temperatures, which can be densified in the gas phase to form solid particles of Pd above 900 °C.
- Pluym, T. C.,Lyons, S. W.,Powell, Q. H.,Gurav, A. S.,Kodas, T. T.,et al.
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- Palladium nanostructures synthesized by radiolysis or by photoreduction
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Palladium nanostructures formed by nanowires, nanoplates or having a flower-like shape were synthesized by slow reduction via radiolysis or via photoreduction of palladium acetylacetonate Pd(acac)2 in 2-propanol under CO atmosphere. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Redjala, Tanafit,Apostolecu, Gabriela,Beaunier, Patricia,Mostafavi, Mehran,Etcheberry, Arnaud,Uzio, Denis,Thomazeau, Cecile,Remita, Hynd
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- Electrodeposited Pd-Co catalyst for direct methanol fuel cell electrodes: Preparation and characterization
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Pd-Co alloy has been recently proposed as a catalyst for the cathode of direct methanol fuel cells with both excellent oxygen reduction activity and methanol tolerance, hence electrodeposition of this alloy is an attractive approach for synthesizing porous metal electrodes with high methanol tolerance in direct methanol fuel cells. In this study, we electrodeposited two types of Pd-Co films onto Au substrates by applying different current density (-10 or -200 mA cm-2); and then characterized them in terms of morphology, composition, crystal structure, and catalytic activity. Pd-Co deposited at -10 mA cm-2 was smooth and possessed smaller particles (ca. 10 nm), while that at -200 mA cm-2 was dendritic (or rough) and possessed larger particles (ca. 50 nm). Both the Pd-Co alloys were found to be almost the same structure, i.e. a solid solution of ca. Pd7Co3 with Pd-skin, and also confirmed to possess comparable activity in oxygen reduction to Pt (potential difference at 1.0 μA cm-2 was 0.05 V). As for methanol tolerance, cell-voltage was not influenced by addition of 1 mol dm-3 methanol to the oxidant solution. Our approach provides fundamental technique for synthesizing Pd-Co porous metal electrodes by electrodeposition.
- Tominaka, Satoshi,Momma, Toshiyuki,Osaka, Tetsuya
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- Facile fabrication of noble metal nanoparticles encapsulated in hollow silica with radially oriented mesopores: Multiple roles of the N-lauroylsarcosine sodium surfactant
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A facile one-pot method was reported to fabricate noble metal nanoparticles encapsulated in silica hollow nanospheres with radially oriented mesopores, and the anionic amino acid surfactant, N-lauroylsarcosine sodium, played multiple roles: reducing agent, stabilizer, emulsion droplets and mesopore template.
- Wang, Hu,Wang, Jin-Gui,Zhou, Hui-Jing,Liu, Yu-Ping,Sun, Ping-Chuan,Chen, Tie-Hong
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- Intramolecular and interionic structural studies of novel olefin palladium(II) and platinum(II) complexes containing poly(pyrazol-1-yl)borate and -methane ligands. X-ray structures of palladium five-coordinate complexes
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Complexes [M(η1,η2-C8H12OMe)(pz2 -YH2)](+) (M = Pd, Y = C, 1; M = Pt, Y = C, 2; M = Pt, Y = B, 3) and [M(η1,η2-C8H12OMe)(pz3 -YH)](+) (M = Pd, Y = C, 4; M = Pd, Y = B, 5; M = Pt, Y = C, 6; M = Pt, Y = B, 7) were synthesized by the reaction of the dimers [M(η1,η2-C8H12OMe)Cl]2 with the poly(pyrazol-1-yl)borate and -methane ligands. Complexes 1-7 were characterized in solution by multinuclear and multidimensional low-temperature NMR spectroscopy. The solid-state structures of olefinic five-coordinate Pd complexes 4 and 5 were investigated by X-ray single-crystal studies. The relative cation-anion position (interionic structure) was investigated in solution, for all cationic complexes at room and low temperature by 19F, 1H-HOESY NMR spectroscopy, and in the solid state for 4. A remarkable specifity of the interionic contacts is observed in solution: the counterion is placed close to the peripheral protons of the pyrazolyl ligands probably due to the partial protection of the apical positions introduced by the nonplanar ligands and the delocalization of the positive charge on the pyrazolyl rings. In the case of complex 4 there is an excellent agreement between the solid state and solution results: the anion selectively interacts with the CH and five protons of the pz3-CH ligand via an assembly of hydrogen bonds.
- Binotti, Barbara,Bellachioma, Gianfranco,Cardaci, Giuseppe,Macchioni, Alceo,Zuccaccia, Cristiano,Foresti, Elisabetta,Sabatino, Piera
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- New formamidine ligands and their mixed ligand palladium(II) oxalate complexes: Synthesis, characterization, DFT calculations and in vitro cytotoxicity
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A series of new ternary palladium(II) complexes of the type [Pd(L1-4)ox]·xH2O where L = formamidine ligands and ox = oxalate, were synthesized and characterized by elemental analyses, magnetic susceptibility, UV-Vis, infrared (IR) and mass spectroscopy and thermal analysis. The spectroscopic data indicated that the formamidine ligands act as bidentate N2 donors and the oxalate as O2 ligand. The complexes (1-4) are diamagnetic and the optimization of their structures indicated that the geometry is distorted square planer with O-Pd-O and N-Pd-N bond angles ranged 82.70-83.87° and 88.21-95.02°; respectively which is acceptable for the heteroleptic complexes. The dipole moment of the complexes (13.97-18.77 Debye) indicating that the complexes are more polarized than the ligands (1.93-4.96 Debye). The complexes are thermally stable as shown from their relatively higher overall activation energies (441-688 kJ mol-1). The ligands and the complexes are proved to have good cytotoxicity with IC50 (μM) in the range of (0.011-0.168) against MCF-7, (0.012-0.150) against HCT-116, (0.042-0.094) against PC-3 and (0.006-0.222) against HepG-2 cell lines, which open the field for further application as antitumor compounds.
- Soliman, Ahmed A.,Alajrawy, Othman I.,Attabi, Fawzy A.,Shaaban, Mohamed R.,Linert
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- Studies on the feasibility of electrochemical recovery of palladium from high-level liquid waste
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The electrochemical behavior of palladium (II) in nitric acid medium has been studied at platinum and stainless steel electrodes by cyclic voltammetry. The cyclic voltammogram consisted of a surge in cathodic current occurring at platinum electrode at a p
- Jayakumar,Venkatesan,Srinivasan,Rao, P.R. Vasudeva
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- Synthesis and reactivity of semibridging borylene complexes
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Reaction of the terminal borylene complexes [(OC)5M=B= N(SiMe3)2] (M = Cr, W) with [M′(PCy3)] (M′ = Pd, Pt) at room temperature led to spontaneous formation of the heterodinuclear complexes [(OC)4M-(μ-CO){μ-BN(SiMe 3)2}M′(PCy3)2] (M = Cr, M′ = Pd; M = W, M′ = Pd; M = Cr, M′ = Pt) with concomitant liberation of PCy3. X-ray diffraction studies revealed that the borylene ligand adopts a semibridging position between the two different metal centers, thus establishing a new coordination mode for borylenes and providing further experimental evidence for the theoretically predicted close relationship between BR and CO. After prolonged reaction times the liberated phosphine substitutes the carbonyl group in trans-position to the borylene moiety, forming complexes of the type [(Cy3P)(OC)3M(μ-CO)-{μ- BN(SiMe3)2}M′(PCy3)] (M = Cr, M′ = Pt; M = W, M′ = Pt; M = W, M′ = Pd). Heating or photolytic activation of [(OC)4M(μ-CO){μ-BN(SiMe3) 2}Pd(PCy3)] afforded the terminal borylene complexes trans-[(Cy3P)(OC)4M=BN(SiMe3)2], which were fully characterized in the case of M = Cr. Structural data of trans-[(Cy3P)(OC)4Cr=BN(SiMe3)2] confirm the presence of an enhanced Cr-B π-back-donation imposed by the phosphine ligand in trans-position.
- Braunschweig, Holger,Radacki, Krzysztof,Rais, Daniela,Uttinger, Katharina
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- Thermal and spectral studies of palladium(II) complexes
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Palladium(II) complexes of type [Pd(L)Cl2] [where L=2-aminopyridine-N-thiohydrazide (L1), (2-aminopyridine-N-thio)-1,3- propanediamine (L2), benzaldehyde 2-aminopyridine-N-thiohydrazone (L3) and salicylaldehyde-2-aminopyridine-N-thiohydrazone (L 4)] have been synthesized. The thiohydrazide, thiodiamine and thiohydrazones can exist as thione-thiol tautomer and coordinate as a bidentate N-S ligand. The ligands found to act in bidentate fashion. The complexes have been characterized by elemental analysis, IR, mass, electronic, 1H NMR spectroscopic studies, and TG/DTA study. Antifungal studies of some complexes were also carried out. Various kinetic and thermodynamic parameters like order of reaction (n), activation energy (E a), apparent activation entropy (S # ) and heat of reaction (ΔH) have also been carried out for one complex.
- Mishra,Mishra,Manav,Kaushik
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- Synthesis and mechanistic study of palladium nanobars and nanorods
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This paper describes a simple and versatile method for growing highly anisotropic nanostructures of Pd, single-crystal nanobars bounded by {100} facets and single-crystal nanorods with their side surfaces enclosed by {100} and {110} facets. According to thermodynamic arguments, Pd atoms should nucleate and grow in a solution phase to form cuboctahedrons of spherical shape with their surfaces bounded by a mix of {111} and {100} facets. Anisotropic nanostructures can only form under kinetically controlled conditions, while the cubic symmetry is broken. In the present system, we found that one-dimensional growth could be induced and maintained through an interplay of the following processes: (i) speedy reduction of the precursor to ensure prompt addition of atoms to the seed; (ii) chemisorption of bromide on the seed to promote the formation of {100} and {110} facets; and (iii) localized oxidative etching on one specific face of the seed to initiate preferential growth on this face. Experimentally, the anisotropic growth can be achieved by varying the type and concentration of reducing agent, as well as by adjusting the reaction temperature. This methodology developed for Pd has also been extended to both Au and Pt. As expected for a kinetically controlled product, the anisotropic nanostructure evolved into the thermodynamically favored shape during an aging process.
- Xiong, Yujie,Cai, Honggang,Wiley, Benjamin J.,Wang, Jinguo,Kim, Moon J.,Xia, Younan
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- Pd colloid-catalyzed methoxycarbonylation of iodobenzene in ionic liquids
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A Pd colloid prepared by reduction of the [Pd(η3-allyl) 2Cl]2 precursor with Vcp2 (vanadocene) in presence of polyvinylpyrrolidone (PVP) as a protecting polymer was found to be an active and stable catalyst of methoxycarbonylation of iodobenzene carried out in an ionic liquid (IL) medium of [bmim]X and/or [bumepy]X (bmim = 1-methyl-3-butyl imidazolium cation, bumepy = 1-butyl-4-methyl pyridinium cation, X = Cl, BF4, PF6) or in the presence of ammonium salts of [R4N]X type (R = nBu, Et, Me; X = Cl, Br, I). The yield of benzoic acid methyl ester produced in methoxycarbonylation of iodobenzene in ionic liquids depends on their structure: those with the pyridinium cation are much more effective than those with the imidazolium one. At the optimal concentration of methanol, the yield of methoxycarbonylation reaction catalyzed by Pd colloid decreases in the order: [nBu 4N]Br > [nBu4N]I > [nBu 4N]Cl > [bumepy]PF6 > [Et4N]Br > [bumepy]Cl > [bumepy]BF4 > [Et4N]Cl > [bmim]PF6 > [bmim]BF4 > [bmim]Cl. A Pd colloid prepared by reduction of the [Pd(η3-allyl)2Cl] 2 precursor with Vcp2 (vanadocene) in the presence of polyvinylpyrrolidone (PVP) as a protecting polymer was found to be an active and stable catalyst of methoxycarbonylation of iodobenzene carried out in an ionic liquid (IL) medium. At the optimal reaction conditions, the yield of methoxycarbonylation catalyzed by Pd colloid decreases in the order: [ nBu4N]Br > [nBu4N]I > [ nBu4N]Cl > [bumepy]PF6 > [Et 4N]Br > [bumepy]Cl > [bumepy]BF4 > [Et 4N]Cl > [bmim]PF6 > [bmim]BF4 > [bmim]Cl.
- Wojtków,Trzeciak,Choukroun,Pellegatta
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- Synthesis, spectral and thermal studies on dicarboxylate-bridged palladium(II) coordination polymers. Part i
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This work describes the synthesis, IR and 13C CPMAS NMR spectroscopic as well the thermal characterization of the new dicarboxylate complexes [Pd2(ox)2(4,4'-bipy)]n (1), [Pd 2(ox)2(bpe)]n (
- Fernandes,Takahashi,Frem,Netto,Mauro,Matos
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- Biochemical Characterization and Antimicrobial Activity against Some Human or Phyto-Pathogens of New Diazonium Heterocyclic Metal Complexes
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String of vanadium (IV), zirconium (IV), palladium (II), platinum (IV) and uranium (VI) chelates of 2-cyano-2-[(2-nitrophenyl)hydrazono]thioacetamide (Cnphta) were prepared and characterized by physicochemical, spectroscopic and thermal analyses. The form
- Camele, Ippolito,El-Attar, Mohamed S.,El-Desoky, Sameh I.,El-Farargy, Ahmed F.,El-Shwiniy, Walaa H.,Elshafie, Hazem S.,Sadeek, Sadeek A.
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- Ligand-controlled and nanoconfinement-boosted luminescence employing Pt(ii) and Pd(ii) complexes: From color-tunable aggregation-enhanced dual emitters towards self-referenced oxygen reporters
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In this work, we describe the synthesis, structural and photophysical characterization of four novel Pd(ii) and Pt(ii) complexes bearing tetradentate luminophoric ligands with high photoluminescence quantum yields (ΦL) and long excited state lifetimes (τ) at room temperature, where the results were interpreted by means of DFT calculations. Incorporation of fluorine atoms into the tetradentate ligand favors aggregation and thereby, a shortened average distance between the metal centers, which provides accessibility to metal-metal-to-ligand charge-transfer (3MMLCT) excimers acting as red-shifted energy traps if compared with the monomeric entities. This supramolecular approach provides an elegant way to enable room-temperature phosphorescence from Pd(ii) complexes, which are otherwise quenched by a thermal population of dissociative states due to a lower ligand field splitting. Encapsulation of these complexes in 100 nm-sized aminated polystyrene nanoparticles enables concentration-controlled aggregation-enhanced dual emission. This phenomenon facilitates the tunability of the absorption and emission colors while providing a rigidified environment supporting an enhancedΦLup to about 80% and extendedτexceeding 100 μs. Additionally, these nanoarrays constitute rare examples for self-referenced oxygen reporters, since the phosphorescence of the aggregates is insensitive to external influences, whereas the monomeric species drop in luminescence lifetime and intensity with increasing triplet molecular dioxygen concentrations (diffusion-controlled quenching).
- Maisuls, Iván,Wang, Cui,Gutierrez Suburu, Matias E.,Wilde, Sebastian,Daniliuc, Constantin-Gabriel,Brünink, Dana,Doltsinis, Nikos L.,Ostendorp, Stefan,Wilde, Gerhard,K?sters, Jutta,Resch-Genger, Ute,Strassert, Cristian A.
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p. 3270 - 3281
(2021/03/17)
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- Synthesis, Structure, DFT, and Biological Activity of Metal Complexes of Norfloxacin and Metformin Mixed Ligand
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Abstract: A new series of mixed ligand metal complexes has been synthesized by the reaction of Co(II), Ni(II), Cu(II), Zr(IV), Pd(II), and Cd(II) with norfloxacin (NOR) and metformin hydrochloride (MF) in 1 : 1 : 1 molar ratio. The complexes have been characterized by FT-IR, UV-Vis, and 1H NMR spectra, TG/DTG and elemental analysis, molar conductance, and magnetic susceptibility data. According to FT-IR, NOR chelates with metal ions as a bidentate ligand via one oxygen of the carboxylate group and pyridone oxygen, and MF chelates with metal ions via two imine groups. Complexes have been identified as electrolytes. Electronic and magnetic data have indicated the octahedral structure for all complexes except square planar Pd(II) complex. Antibacterial and antifungal activities of the compounds have been tested against several species, and have indicated higher inhibition against micro-organisms for the metal complexes than the mixed ligands.
- Abbass, L. M.,El-Shwiniy, W. H.,El-Telbany, M.,Sadeek, S. A.,Zordok, W. A.
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p. 1774 - 1782
(2021/11/01)
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- Synthesis, physico-chemical characterization and bioevaluation of Ni(II), Pd(II), and Pt(II) complexes with 1-(o-tolyl)biguanide: Antimicrobial and antitumor studies
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New complexes of type [M(tbg)2]Cl2 [tbg = 1-(o-tolyl)biguanide; M = Ni(II), Pd(II), and Pt(II)] were synthesized and characterized to develop new biologically active compounds. The features of the complexes were assigned from microanalytical and thermal data. The NMR, FT-IR, and UV-Vis spectra were established by comparison with HtbgCl. All complexes exhibit a square-planar geometry resulting from the chelating behavior of tbg. The HtbgCl and [Ni(tbg)2]Cl2 complexes were fully characterized by single-crystal X-ray diffraction. The HtbgCl species crystallize in the monoclinic C2/c spatial group, while the Ni(II) complex adopts an orthorhombic Pna21 spatial group. The structure is stabilized by a complex hydrogen bonds network. The in vitro antimicrobial assays revealed improved antimicrobial activity for complexes in comparison with the ligand against both planktonic and biofilm embedded microbial cells. The most efficient compound, showing the largest spectrum of antimicrobial activity, including Gram-positive and Gram-negative bacteria, as well as fungal strains, in both planktonic and biofilm growth states was the Pd(II) complex, followed by the Pt(II) complex. The Pt(II) compound exhibited the most significant antiproliferative activity on the human cervical cancer SiHa cell line, inducing a cell cycle arrest in the G2/M phase.
- Nu??, Ileana,Badea, Mihaela,Chifiriuc, Mariana Carmen,Bleotu, Coralia,Popa, Marcela,Daniliuc, Constantin-Gabriel,Olar, Rodica
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- New perspective of a nano-metal preparation pathway based on the hexahydro-closo-hexaborate anion
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Today, metal-based nanomaterials play an increasingly important role in the energy, environment, medical and health fields. In order to meet the needs of various fields, it is necessary to continuously develop advanced technologies for preparing metal-based materials. Inspired by previous research, the results of a proof-of-concept experiment show that the hexahydro-closo-hexaborate anion (closo-[B6H7]?) in the borane cluster family has properties similar to NaBH4.Closo-[B6H7]?can not only convert common precious metal ions such as Au3+, Pd2+, Pt4+and Ag+to the corresponding zero-valence state, but also convert some non-precious metals such as Cu2+and Ni2+to the zero-valent or oxidation state.Closo-[B6H7]?moderate reduction to cause rapid aggregation of metal-based materials is not easy compared with NaBH4. Compared withcloso-[B12H12]2?,closo-[B6H7]?achieves the conversion of Pt4+to Pt0under ambient conditions, and its reduction performance extends to non-precious metals. The excellent stability and easy modification characteristics determine the universality of thecloso-[B6H7]?reduction strategy for metal ions.
- Liu, Jun,Zhang, Haibo,Zhao, Xue
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p. 33444 - 33449
(2020/09/21)
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- Oxidative ring expansion of a low-coordinate palladacycle: Synthesis of a robust T-shaped alkylpalladium(II) complex
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The synthesis of an unusual T-shaped alkylpalladium(II) complex featuring a cyclometalated tri-tert-butylphosphineoxide ligand by oxidation of the corresponding cyclometalated tri-tert-butylphosphine complex with PhIO is reported. We speculate that this reaction proceeds by formation of a transient palladium oxo intermediate and there are structural similarities with a late transition metal exemplar: Milstein's seminal pincer ligated Pt(IV) oxo (Nature 2008, 455, 1093–1096).
- Sinclair, Matthew J.G.,Chaplin, Adrian B.
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- Detection and characterization of mononuclear Pd(I) complexes supported by N2S2 and N4 tetradentate ligands
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Palladium is a versatile transition metal used to catalyze a large number of chemical transformations, largely due to its ability to access various oxidation states (0, I, II, III, and IV). Among these oxidation states, Pd(I) is arguably the least studied, and while dinuclear Pd(I) complexes are more common, mononuclear Pd(I) species are very rare. Reported herein are spectroscopic studies of a series of Pd(I) intermediates generated by the chemical reduction at low temperatures of Pd(II) precursors supported by the tetradentate ligands 2,11-dithia[3.3](2,6)pyridinophane (N2S2) and N,N′-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane (tBuN4): [(N2S2)PdII(MeCN)]2(OTf)4 (1), [(N2S2)-PdIIMe]2(OTf)2 (2), [(N2S2)PdIICl](OTf) (3), [(N2S2)PdIIX](OTf)2 (X = tBuNC 4, PPh3 5), [(N2S2)PdIIMe(PPh3)](OTf) (6), and [(tBuN4)PdIIX2](OTf)2 (X = MeCN 8, tBuNC 9). In addition, a stable Pd(I) dinuclear species, [(N2S2)PdI(μtBuNC)]2(ClO4)2 (7), was isolated upon the electrochemical reduction of 4 and structurally characterized. Moreover, the (tBuN4)PdI intermediates, formed from the chemical reduction of [(tBuN4)PdIIX2](OTf)2 (X = MeCN 8, tBuNC 9) complexes, were investigated by EPR spectroscopy, X-ray absorption spectroscopy (XAS), and DFT calculations and compared with the analogous (N2S2)PdI systems. Upon probing the stability of Pd(I) species under different ligand environments, it is apparent that the presence of soft ligands such as tBuNC and PPh3 significantly improves the stability of Pd(I) species, which should make the isolation of mononuclear Pd(I) species possible.
- Luo, Jia,Mirica, Liviu M.,Rath, Nigam P.,Tran, Giang N.
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supporting information
p. 15659 - 15669
(2020/11/20)
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- Oxidant/complexing properties of the methimazole (MeImHS)/iodine system towards palladium and gold metals. Crystal structure of the complex cation [PdII(MeImHS)4]2+ balanced by a tetraiodide/iodide mixture
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This paper reports on the oxidative dissolution ability in dichloromethane and water of the methimazole-iodine system towards gold and palladium in powder. This research has a potential application in the recovery process of these metals from electrical and electronic waste equipment (WEEE). The iodine-adduct of methimazole (1-methyl-3H-imidazole-2-thione; MeImHS) oxidises gold and palladium powders in dichloromethane to form the complexes [AuI(MeImHS)2]I3 and [PdII(MeImHS)4](I4)0.73·2(I)0.27. The X-ray crystal structure of the palladium complex shows a square-planar Pd(ii) ion S-coordinated to four MeImHS units with the charge essentially balanced by an unusual tetraiodide I42- with minor amounts of iodide. The oxidative dissolution of palladium in water medium produces the cation [PdII(MeImHS)4]2+. Considering the reaction conditions under which the process was performed ([I2] = 1.14 × 10-3 M, T = 20 °C, pH = 5, reaction time 24 h), the obtained value of 64% of oxidation yields from Pd(0) to Pd(ii) is to be considered satisfactory. No appreciable oxidation was observed for the gold powder in water. The feasibility of recovering palladium from the triiodide salt of the complex cation [PdII(MeImHS)4]2+ was verified by carrying out a two-step reduction process using magnesium powder.
- Isaia, Francesco,Aragoni, Maria Carla,Arca, Massimiliano,Caltagirone, Claudia,Castellano, Carlo,Demartin, Francesco,Garau, Alessandra,Lippolis, Vito,Pivetta, Tiziana
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p. 2652 - 2660
(2020/02/20)
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- Tunable synthesis of multiply twinned intermetallic Pd3Pb nanowire networks toward efficient N2 to NH3 conversion
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Atomically ordered intermetallic nanocrystals have been extensively explored in electrocatalysis due to their outstanding catalytic performances and excellent stabilities. However, controllable synthesis of intermetallic nanocrystals in terms of their size and structure remains a grand challenge due to the generally involved high-temperature thermal annealing synthetic method, largely hindering the optimization of their catalytic properties. Herein, we report a versatile approach to the synthesis of atomically ordered Pd3Pb multiply twinned intermetallic nanowire networks (MT-IM-NNs) with a tunable diameter and microstructure. The use of preformed Pd seeds, which were converted to a Pd3Pb intermetallic phase via the diffusion of Pb atoms into the seeds, as well as an oriented attachment growth mode, accounted for the formation of such a unique structure. Importantly, the diameter and microstructure of Pd3Pb MT-IM-NNs could be engineered by controlling the size and type of Pd seeds. In addition, the Pd3Pb multiply twinned intermetallic porous nanowire networks exhibited a high faradaic efficiency of 21.46% and an NH3 yield rate of 18.2 μg h-1 mgcat-1 at-0.2 V vs. the reversible hydrogen electrode toward N2 electroreduction.
- Guo, Jingchun,Wang, Hui,Xue, Fei,Yu, Dan,Zhang, Li,Jiao, Shilong,Liu, Yihui,Lu, Yangfan,Liu, Maochang,Ruan, Shuangchen,Zeng, Yu-Jia,Ma, Chao,Huang, Hongwen
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p. 20247 - 20253
(2019/09/18)
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- Two-step synthesis of Ir-decorated Pd nanocubes and their impact on the glycerol electrooxidation
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Despite intense research to synthesize well-ordered noble-metals nanoparticles to understand catalyzed electrochemical reactions, the synthesis and application of multi-metallic well-ordered nanomaterials is still rare. Here, we report a facile strategy for synthesizing Ir-decorated Pd nanocubes (NCs) in one-batch through two sequential chemical reduction processes. Afterwards, the activity of these materials was investigated for glycerol electrooxidation in alkaline medium by cyclic voltammetry and in situ FTIR. Microscopy images and compositional mapping reveal that Ir deposition barely changes the size of the cubes. The bi-metallic nanocubes shifts the onset potential toward lower values, but decreases the current density. The start potential displacement is rationalized as a consequence of a facilitated CO removal and an anticipated carbonate production; while the decrease in current may be a consequence of a reaction with multiple steps, each one extracting a few electrons. FTIR in situ spectra reveal CO2 production only for Ir-Pd NCs, which is due to a massive production of carbonate, which ultimately acidifies the interfacial pH. The protocol of synthesis showed here may be used to study well-ordered multimetallic nanostructures in several applications, not limited for electrocatalysis.
- Zanata, Cinthia R.,Martins, Cauê A.,Teixeira-Neto, érico,Giz, Martha J.,Camara, Giuseppe A.
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p. 358 - 366
(2019/08/12)
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- Green catalytic synthesis of 5-methylfurfural by selective hydrogenolysis of 5-hydroxymethylfurfural over size-controlled Pd nanoparticle catalysts
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A green approach for the conversion of 5-(hydroxymethyl)furfural (HMF) to 5-methylfurfural (MF) by using size-controlled palladium catalysts has been developed. Palladium nanoparticles (Pd NPs) with various sizes supported on activated carbon were prepared with polyvinylpyrrolidone (PVP) as the capping agent. The reaction results showed that all the PVP-assisted Pd catalysts achieved high selectivity whilst the hydrogenation ability of Pd NPs could be rationally tuned by varying the mole ratio of Pd/PVP. 2.5% Pd-PVP/C (1:2) presented a satisfactory activity with 80% MF yield and 90% selectivity. The reaction kinetics study showed that the transformation of HMF into MF over bifunctional PVP-assisted Pd NPs underwent an acid-catalyzed esterification followed by a Pd-catalyzed hydrogenolysis procedure. The role of formic acid in the transformation is not only as a hydrogen-donating agent but also as a reactant to form the key intermediate. This work provides a novel and environmentally-friendly method for the selective hydrogenation of bio-based HMF to MF.
- Sun, Guohan,An, Jiahuan,Hu, Hong,Li, Changzhi,Zuo, Songlin,Xia, Haian
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p. 1238 - 1244
(2019/03/11)
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- Supramolecular Host-Selective Activation of Iodoarenes by Encapsulated Organometallics
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Supramolecular hosts offer defined microenvironments that facilitate selective host-guest interactions, enabling reactivity that would otherwise be challenging in bulk solution. While impressive rate enhancements and selectivities have been reported, similar reactivity can often be accessed through modifications of reaction conditions even in the absence of the host. We report here an oxidative addition of aryl halides across the metal centers in Cu(I) and Pd(II) organometallics that is assisted by the presence of a supramolecular host, realized via electrostatic stabilization and increased local substrate concentrations. When reaction conditions were screened to assess background reactivity, alternative reactivity (typically decomposition) resulted, indicating that encapsulation led to host-selective reaction trajectories.
- Bender, Trandon A.,Morimoto, Mariko,Bergman, Robert G.,Raymond, Kenneth N.,Toste, F. Dean
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supporting information
p. 1701 - 1706
(2019/04/11)
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- Pd-Colloids-Catalyzed/Ag2O-Oxidized General and Selective Esterification of Benzylic Alcohols
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Palladium colloids obtained from the degradation of Hermann–Beller palladacycle proved to be an efficient catalytic system in combination with silver oxide as a selective oxidant for the oxidative esterification of differently substituted benzyl alcohols in MeOH as solvent. Excellent reactivity exhibited by the catalytic system also allowed the alcoholic coupling partner to be changed from MeOH to a wide range of alcohols having diverse functionalities. The mildness of the developed protocol also made it possible to employ propargyl alcohol as the coupling partner without any observation of any interference of the terminal alkyne. Selective oxidative coupling of a primary alcoholic functional group over secondary in the case of glycols and glycerols was also made possible using the developed catalyst system. To test the relevancy of Pd/Ag combined catalysis mixed Pd/Ag colloids were synthesized, characterized by TEM, XRD and XPS and applied to oxidative-esterification successfully.
- Sable, Vaibhav,Shah, Jagrut,Sharma, Anuja,Kapdi, Anant R.
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supporting information
p. 2639 - 2647
(2019/07/08)
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- C(sp3)-C(sp3) Coupling with a Pd(II) Complex Bearing a Structurally Responsive Ligand
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A dimer with two PdII-Me fragments is stabilized by the bridging coordination of the supporting 1-azaallyl/phosphine ligand. Heating the complex results in C(sp3)-C(sp3) bond formation and the release of ethane. Two different palladium products are generated, each with distinct coordination modes of the 1-azaallyl/phosphine ligand.
- Jackman, Kyle M. K.,Bridge, Benjamin J.,Sauve, Ethan R.,Rowley, Christopher N.,Zheng, Cameron H. M.,Stubbs, James M.,Boyle, Paul D.,Blacquiere, Johanna M.
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p. 1677 - 1681
(2019/04/30)
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- Homoleptic cis- and trans-palladium(II) bis(guanidinato) complexes derived from N-aryl-N′,N″-di(pyridin-2-yl)- and N-aryl-N′,N″-bis(6-methylpyridin-2-yl)guanidines: Catalysts for Heck-Mizoroki coupling reactions
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N-Aryl-N′,N″-di(pyridin-2-yl)- and N-aryl-N′,N″-bis(6-methylpyridin-2-yl)guanidines (1–4 and 5–7) were isolated in 75%–81% yields. Reactions of Pd(OAc)2 with guanidines 2–7 carried out separately in toluene at 60 °C for 3 h afforded 8–13 respectively in 69%–80% yields. Compounds 1–13 were characterized by elemental analyses, HR-MS, IR and NMR (1H and 13C) spectroscopy. Molecular structures of guanidines 1, 4, 5 and 6 and those of 8–13 were determined by single crystal X-ray diffraction. The Pd(II) atom in 8–10 revealed trans geometry while that in 11–13 revealed cis geometry. DFT calculations were carried out on model compounds 9a (trans) and its hypothetical cis isomer, 9b and 12a (cis) and its hypothetical trans isomer 12b which indicated a very small energy difference between the 9a/9b pair (1.28 kcal/mol) whereas a large energy difference was observed between the 12a/12b pair (26.38 kcal/mol) in CH2Cl2. The catalytic utility of 9 in Heck-Mizoroki coupling reactions involving styrene and methyl acrylate and aryl bromides/aryl chlorides in the presence of NaOAc and excess of tetrabutylammonium bromide (TBAB) at 120 °C was explored. Both activated and de-activated aryl bromides and aryl chlorides were coupled with styrene and in addition, the aryl chlorides were coupled with methyl acrylate in the presence of 9 to afford the respective coupling products in 68% ? >99% yields. Neat reaction carried out with 9 and TBAB under the optimized condition released the colloidal Pd black as verified by EDAX, PXRD and SEM techniques thereby implying the heterogeneous nature of catalysis.
- Mishra, Vishwesh,Thomas, Jisha Mary,Chinnappan, Sivasankar,Thirupathi, Natesan
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- Synthesis of Polyethylene with In-Chain α,β-Unsaturated Ketone and Isolated Ketone Units: Pd-Catalyzed Ring-Opening Copolymerization of Cyclopropenone with Ethylene
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Although various functionalized units can be incorporated into polyolefins by transition metal catalyzed coordination copolymerizations of nonfunctionalized olefins with polar functional monomers, the incorporated functional units are largely limited to a C1 unit from either CO or C2 units from vinyl monomers. Reported here is the Pd-catalyzed copolymerization of ethylene with cyclopropenone, leading to incorporation of C3 units with functional groups, α,β-unsaturated ketones, in the chain. Coordination-insertion of the carbonyl group and ring opening of the strained three-membered ring are proposed as the key steps in the mechanism. Under different reaction conditions an isolated ketone structure was afforded as the major carbonyl unit, and could be generated by the copolymerization of ethylene with CO formed in situ from cyclopropenone.
- Wang, Xiaoming,Seidel, Falk William,Nozaki, Kyoko
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supporting information
p. 12955 - 12959
(2019/08/21)
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- The ubiquitous cross-coupling catalyst system 'Pd(OAc)2'/2PPh3 forms a unique dinuclear PdI complex: An important entry point into catalytically competent cyclic Pd3 clusters
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Palladium(ii) acetate 'Pd(OAc)2'/nPPh3 is a ubiquitous precatalyst system for cross-coupling reactions. It is widely accepted that reduction of in situ generated trans-[Pd(OAc)2(PPh3)2] affords [Pd0(PPh3)n] and/or [Pd0(PPh3)2(OAc)]- species which undergo oxidative addition reactions with organohalides-the first committed step in cross-coupling catalytic cycles. In this paper we report for the first time that reaction of Pd3(OAc)6 with 6 equivalents of PPh3 (i.e. a Pd/PPh3 ratio of 1?:?2) affords a novel dinuclear PdI complex [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] as the major product, the elusive species resisting characterization until now. While unstable, the dinuclear PdI complex reacts with CH2Cl2, p-fluoroiodobenzene or 2-bromopyridine to afford Pd3 cluster complexes containing bridging halide ligands, i.e. [Pd3(X)(PPh2)2(PPh3)3]X, carrying an overall 4/3 oxidation state (at Pd). Use of 2-bromopyridine was critical in understanding that a putative 14-electron mononuclear 'PdII(R)(X)(PPh3)' is released on forming [Pd3(X)(PPh2)2(PPh3)3]X clusters from [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2]. Altering the Pd/PPh3 ratio to 1?:?4 forms Pd0(PPh3)3 quantitatively. In an exemplar Suzuki-Miyaura cross-coupling reaction, the importance of the 'Pd(OAc)2'/nPPh3 ratio is demonstrated; catalytic efficacy is significantly enhanced when n = 2. Employing 'Pd(OAc)2'/PPh3 in a 1?:?2 ratio leads to the generation of [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] which upon reaction with organohalides (i.e. substrate) forms a reactive Pd3 cluster species. These higher nuclearity species are the cross-coupling catalyst species, when employing a 'Pd(OAc)2'/PPh3 of 1?:?2, for which there are profound implications for understanding downstream product selectivities and chemo-, regio- and stereoselectivities, particularly when employing PPh3 as the ligand.
- Scott, Neil W. J.,Ford, Mark J.,Schotes, Christoph,Parker, Rachel R.,Whitwood, Adrian C.,Fairlamb, Ian J. S.
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p. 7898 - 7906
(2019/09/06)
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- The Effect of Particle Size and the Modifier on the Properties of Palladium Catalysts in the Synthesis of Hydrogen Peroxide by the Anthraquinone Method
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The effect of the composition of the catalytic system and the size of particles on the properties of palladium catalysts in 2-ethyl-9,10-anthraquinone hydrogenation was studied. It was shown that, depending on the nature of a reducing agent (H2, AlEt3), palladium species formed in the absence of a modifying agent catalyze various side processes to a substantial extent together with 2-ethyl-9,10-anthraquinone hydrogenation: mostly hydrogenolysis (in the case of H2 as a reducing agent) and hydrogenation of aromatic rings in 2-ethyl-9,10-anthrahydroquinone (in the case of AlEt3 as a reducing agent). Elementary phosphorus was found to have a promoting effect on the selectivity of palladium catalysts in the synthesis of hydrogen peroxide by the anthraquinone method. The main factors that make it possible to control the selectivity of palladium catalysts were discussed.
- Belykh, L. B.,Gvozdovskaya, K. L.,Sanzhieva, S. B.,Schmidt, F. K.,Skripov, N. I.,Sterenchuk, T. P.
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p. 585 - 592
(2018/10/02)
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- Ice Melting to Release Reactants in Solution Syntheses
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Aqueous solution syntheses are mostly based on mixing two solutions with different reactants. It is shown that freezing one solution and melting it in another solution provides a new interesting strategy to mix chemicals and to significantly change the reaction kinetics and thermodynamics. For example, a precursor solution containing a certain concentration of AgNO3 was frozen and dropped into a reductive NaBH4 solution at about 0 °C. The ultra-slow release of reactants was successfully achieved. An ice-melting process can be used to synthesize atomically dispersed metals, including cobalt, nickel, copper, rhodium, ruthenium, palladium, silver, osmium, iridium, platinum, and gold, which can be easily extended to other solution syntheses (such as precipitation, hydrolysis, and displacement reactions) and provide a generalized method to redesign the interphase reaction kinetics and ion diffusion in wet chemistry.
- Wei, Hehe,Huang, Kai,Zhang, Le,Ge, Binghui,Wang, Dong,Lang, Jialiang,Ma, Jingyuan,Wang, Da,Zhang, Shuai,Li, Qunyang,Zhang, Ruoyu,Hussain, Naveed,Lei, Ming,Liu, Li-Min,Wu, Hui
-
supporting information
p. 3354 - 3359
(2018/02/21)
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- Complex salts of Pd(ii) and Pt(ii) with Co(ii) and Ni(ii) aqua-cations as single-source precursors for bimetallic nanoalloys and mixed oxides
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A series of highly soluble double complex salts [M′(H2O)6][M′′(NO2)4]·2H2O (M′ = Ni, Co; M′′ = Pd, Pt) have been synthesized, studied and used as single-source precursors for bimetallic nanoalloys and metal-oxide composites. According to the results of simultaneous thermal analysis-mass spectrometry (STA-MS), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), thermolysis of the compounds in diverse atmospheres (O2, He, and H2), delafossite-type mixed oxides M′′CoO2/(NiO + M′′O), metal-oxide composition M′O + M′′ and bimetallic solid solution M′0.5M′′0.5, respectively. In an H2 atmosphere an instant isolation of the equiatomic solid solution occurs at lower than 200 °C with simultaneous reduction of noble and ignoble metals. The bimetallic products can be superstructurally ordered at higher temperatures. The solubility of precursors in organic solvents allows carrying out an impregnation of the salts inside multiwalled carbon nanotubes; subsequent heating in H2 yields intercalated nanoparticles of ~2-4 nm in size.
- Zadesenets, Andrey V.,Filatov, Evgeniy Yu.,Plyusnin, Pavel E.,Asanova, Tatyana I.,Korolkov, Ilya V.,Baidina, Iraida A.,Shlyakhova, Elena V.,Asanov, Igor P.,Korenev, Sergey V.
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p. 8843 - 8850
(2018/06/08)
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- Synthesis, Properties, and Catalytic Application of a Triptycene-Type Borate-Phosphine Ligand
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A borate-containing caged triarylphosphine L-X (X = Na or NBu4), featuring a 9-phospha-10-boratriptycene framework, was synthesized and characterized by NMR spectroscopy and X-ray diffraction analysis. The NMR coupling constant of the corresponding phosphine selenide indicated a higher electron-donating property of the borate-phosphine L compared to that of the 9-phospha-10-silatriptycene derivative (Ph-TRIP). The coordination property of L-X to [PdCl(η3-allyl)]2 was dependent on the countercation, giving a neutral Pd complex [PdCl(η3-allyl)(L-NBu4)] from L-NBu4 in CH2Cl2 or a zwitterionic Pd complex [Pd(η3-allyl)(MeCN)(L)] from L-Na in MeCN/CH2Cl2. Utility of L-X as a ligand for metal catalysis was demonstrated in the Pd-catalyzed Suzuki-Miyaura cross-coupling of aryl chlorides.
- Konishi, Shota,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 1876 - 1883
(2018/07/05)
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- Olefin Dimerization and Isomerization Catalyzed by Pyridylidene Amide Palladium Complexes
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A series of cationic palladium complexes [Pd(N^N′)Me(NCMe)]+ was synthesized, comprising three different N^N′-bidentate coordinating pyridyl-pyridylidene amide (PYA) ligands with different electronic and structural properties depending on the PYA position (o-, m-, and p-PYA). Structural investigation in solution revealed cis/trans isomeric ratios that correlate with the donor properties of the PYA ligand, with the highest cis ratios for the complex having the most donating o-PYA ligand and lowest ratios for that with the weakest donor p-PYA system. The catalytic activity of the cationic complexes [Pd(N^N′)Me(NCMe)]+ in alkene insertion and dimerization showed a strong correlation with the ligand setting. While complexes bearing more electron donating m- and o-PYA ligands produced butenes within 60 and 30 min, respectively, the p-PYA complex was much slower and only reached 50% conversion of ethylene within 2 h. Likewise, insertion of methyl acrylate as a polar monomer was more efficient with stronger donor PYA units, reaching a 32% ratio of methyl acrylate vs ethylene insertion. Mechanistic investigations about the ethylene insertion allowed detection, for the first time, by NMR spectroscopy both cis- and trans-Pd-ethyl intermediates and, furthermore, revealed a trans to cis isomerization of the Pd-ethyl resting state as the rate-limiting step for inducing ethylene conversion. These PYA palladium complexes induce rapid double-bond isomerization of terminal to internal alkenes through a chain-walking process, which prevents both polymerization and also the conversion of higher olefins, leading selectively to ethylene dimerization.
- Navarro, Miquel,Rosar, Vera,Montini, Tiziano,Milani, Barbara,Albrecht, Martin
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p. 3619 - 3630
(2018/10/05)
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- Palladium alkyl complexes with a formazanate ligand: Synthesis, structure and reactivity
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Palladium(ii) complexes with a bidentate, anionic formazanate ligand are described. Attempts to prepare mono(formazanate) palladium alkyl complexes often leads to the homoleptic bis(formazanate) complex, which shows rich electrochemistry due to the redox-active nature of the ligands. Performing salt metathesis between the precursor [Pd(COD)(CH3)Cl] and the potassium salt of the ligand in the presence of tetrabutylammonium chloride yields a square planar mono(formazanate) palladate complex through coordination of chloride anion. Ligand exchange allows binding of unsaturated molecules and evaluation of the reactivity of the Pd-CH3 fragment. Using this approach, insertion reactions of CO, isocyanide and methyl acrylate into the Pd-CH3 bond are demonstrated.
- Milocco, Francesca,De Vries, Folkert,Dall'Anese, Anna,Rosar, Vera,Zangrando, Ennio,Otten, Edwin,Milani, Barbara
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supporting information
p. 14445 - 14451
(2018/10/31)
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- Thermal behavior study of palladium(II) complexes containing the iminic ligand N,N′-bis(3,4-dimethoxybenzaldehyde) ethane-1,2-diamine
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This study describes the synthesis, characterization and thermal behavior study of the Schiff base N,N′-bis(3,4-dimethoxybenzaldehyde)ethane-1,2-diamine (C.1) and four new compounds of palladium(II) N,N-chelate coordination, with the general formula [Pd(X1)(X2)(3,4dm-1,2am)] where 3,4dm-1,2am=N,N′-bis(3,4-dimethoxybenzaldehyde)ethane-1,2-diamine, X1 = X2 = Cl? (C.2), X1 = X2 = Cl? and Br? (C.3), X1 = X2 = N3? (C.4) and X1 = X2 = NCO? (C.5). The compounds were characterized by elemental analysis, infrared vibrational spectroscopy (IR) and nuclear magnetic resonance (NMR) 1H and 13C. The TG/DTA curves showed that the thermal decomposition of the C2–C.5 complexes occurred in steps that involve the removal of both inorganic and organic ligand, and palladium oxidation steps forming palladium(II) oxide followed by the reduction of PdO into Pd(0), this being the constituent of the residual mass observed at the end of the TG curves, which have values consistent with the expected ones. The formed compounds can be ordered according to thermal stability considering the initial decomposition temperature (C.5 > C.2 > C.3 > C.4).
- Xavier,de Gois,Sarto,de Almeida
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p. 1829 - 1837
(2018/06/11)
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- Ligand-Induced Reductive Elimination of Ethane from Azopyridine Palladium Dimethyl Complexes
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Reductive elimination (RE) is a critical step in many catalytic processes. The reductive elimination of unsaturated groups (aryl, vinyl and ethynyl) from Pd(II) species is considerably faster than RE of saturated alkyl groups. Pd(II) dimethyl complexes ligated by chelating diimine ligands are stable toward RE unless subjected to a thermal or redox stimulus. Herein, we report the spontaneous RE of ethane from (azpy)PdMe2 complexes and the unique role of the redox-active azopyridine (azpy) ligands in facilitating this reaction. The (azpy)PdMe2 complexes are air- and moisture-stable in the solid form, but they readily produce ethane upon dissolution in polar solvents at temperatures from 10 °C to room temperature without the need for an external oxidant or elevated temperatures. Experimental and computational studies indicate that a bimolecular methyl transfer precedes the reductive elimination step, where both steps are facilitated by the redox-active azopyridine ligand.
- Rudenko, Andrey E.,Clayman, Naomi E.,Walker, Katherine L.,Maclaren, Jana K.,Zimmerman, Paul M.,Waymouth, Robert M.
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supporting information
p. 11408 - 11415
(2018/09/12)
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- Gallic acid-derived palladium(0) nanoparticles as in situ-formed catalyst for Sonogashira cross-coupling reaction in ethanol under open air
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A simple and eco-friendly protocol using gallic acid-derived palladium(0) nanoparticles as in situ-formed catalyst for Sonogashira reactions in ethanol under optimum thermal conditions have been developed. Excellent yields were obtained with the addition of a small amount of gallic acid (1 mol%) to the reaction mixture. The formation of the PdNPs was confirmed by using UV/Vis spectroscopy, and their size and morphology were determined by TEM and XRD analysis. Both aliphatic and aromatic terminal alkynes displayed efficient reactivity with the catalytic system. Moreover, the reaction condition is highly compatible with less reactive aryl bromides at moderate temperature, and further can be reused repeatedly up to four cycles. Since gallic acid is a non-toxic naturally abundant phytochemical, the present method provides an efficient alternative route for Sonogashira reaction with natural feedstock as additive.
- Sarmah, Manashi,Mondal, Manoj,Gohain, Shivanee Borpatra,Bora, Utpal
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- Mesoporous PdxPt alloys: High-performance catalysts for methane combustion
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Mesoporous cubic PdxPt (x = 0.43–8.52) alloys with surface areas of 26–32 m2/g were synthesized using the KIT-6-templating method. Physicochemical properties of the materials were characterized by means of various techniques, and their catalytic activities were evaluated for methane combustion. It is found that the Pd and Pt were uniformly distributed in the PdxPt alloys. The addition of Pt to Pd exerted a significant effect on the redox property of Pd. The PdxPt alloys possessed a higher methane activation ability than the monometallic Pd. The oxidized Pd–Pt (i.e., PdO–PtO2) were more active than the metallic Pd0–Pt0. The Pd2.41Pt sample performed the best for methane combustion (T10%, T50%, and T90% were 272, 303, and 322 °C at SV = 100,000 mL/(g h); TOFPd, TOFPt, TOFPd + Pt, and specific reaction rate at 280 °C were 0.85 × 10?3 s?1, 1.98 × 10?3 s?1, 0.59 × 10?3 s?1, and 4.46 μmol/(gcat s), respectively). The deactivation of the Pd2.41Pt sample induced by 2.5–5.0 vol% CO2 or H2O addition was reversible, but its deactivation due to 100 ppm SO2 introduction was irreversible. It is concluded that the excellent catalytic performance of the Pd2.41Pt sample was associated with its good mesoporous structure, Pd–Pt alloy and PdO–PtO2 coexistence, and good methane and oxygen activation ability.
- Zhao, Xingtian,Liu, Yuxi,Deng, Jiguang,Xu, Peng,Yang, Jun,Zhang, Kunfeng,Han, Zhuo,Dai, Hongxing
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p. 191 - 201
(2017/10/30)
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- Singlet oxygen-engaged selective photo-oxidation over pt nanocrystals/porphyrinic MOF: The roles of photothermal effect and pt electronic state
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The selectivity control toward aldehyde in the aromatic alcohol oxidation remains a grand challenge using molecular oxygen under mild conditions. In this work, we designed and synthesized Pt/PCN-224(M) composites by integration of Pt nanocrystals and porphyrinic metal-organic frameworks (MOFs), PCN-224(M). The composites exhibit excellent catalytic performance in the photo-oxidation of aromatic alcohols by 1 atm O2 at ambient temperature, based on a synergetic photothermal effect and singlet oxygen production. Additionally, in opposition to the function of the Schottky junction, injection of hot electrons from plasmonic Pt into PCN-224(M) would lower the electron density of the Pt surface, which thus is tailorable for the optimized catalytic performance via the competition between the Schottky junction and the plasmonic effect by altering the light intensity. To the best of our knowledge, this is not only an unprecedented report on singlet oxygen-engaged selective oxidation of aromatic alcohols to aldehydes but also the first report on photothermal effect of MOFs.
- Chen, Yu-Zhen,Wang, Zhiyong U.,Wang, Hengwei,Lu, Junling,Yu, Shu-Hong,Jiang, Hai-Long
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p. 2035 - 2044
(2017/02/15)
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- New double complex salt [PdEn2]3[Rh(NO2)6]2 · 2.67H2O: Synthesis, crystal structure, and thermal properties
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The crystal structure of the double complex salt (DCS) [PdEn2]3[Rh(NO2)6]2 ? 2.67H2O (I) has been determined by X-ray diffraction. Crystals are triclinic, space group P1 ˉ , Z = 4, a = 9.2331(3) ?, b = 9.9136(4) ?, c = 13.7824(5) ?, α = 84.3230(14)°, β = 89.9655(14)°, γ = 66.7272(13)°, V = 1152.19(7) ?3, ρcalcd = 2.141 g/cm3, R = 0.0279. The thermal behavior of complex salt I has been studied in various gas atmospheres. The end product of thermolysis in reductive atmosphere is a mixture of Pd0.45Rh0.55 and Pd0.95Rh0.05 solid solutions. The end product of thermolysis in an inert atmosphere is a homogeneous Pd0.6Rh0.4 solid solution.
- Kirilovich,Plyusnin,Piryazev,Gromilov,Korenev
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p. 886 - 892
(2017/08/10)
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- Gold and palladium oxidation/complexation in water by a thioamide-iodine leaching system
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This paper concerns the oxidative dissolution ability of a thioamide/iodine leaching system in water towards gold, palladium and silver metals in powder in view of a potential application in the recovery process of these metals from electrical and electronic waste equipment (E-waste). The leaching mixture composed of equimolar amounts of thioamide 3-methyl-benzothiazole-2-thione and I2 in water can oxidize/complex gold and palladium metals in powder in order to form the complexes [AuI(mbtt)2]I3 and [PdII(mbtt)3I]I3. Considering the mild conditions under which the processes were performed ([I2] = 1.14 × 10-3 M, T = 20 °C, pH = 5.0, leaching time = 24 h), the obtained oxidation yield of Au0 and Pd0 are to be considered satisfactory with values of 65% and 69%, respectively. No oxidation was observed for the silver powder. The oxidising/complexing properties of the leaching mixture mbtt + I2 were interpreted considering the formation of the mbtt-I2 adduct that features, as a consequence of the S-donor to I2 interaction, a charge separation between the bridging and terminal iodine atoms in the fragment S-Ib-It. The feasibility of recovering gold from the complex [AuI(mbtt)2]I3 was verified by performing a cementation with magnesium powder.
- Isaia, Francesco,Aragoni, Maria Carla,Arca, Massimiliano,Caltagirone, Claudia,Castellano, Carlo,De Filippo, Greta,Garau, Alessandra,Lippolis, Vito,Pivetta, Tiziana
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p. 4591 - 4599
(2017/10/13)
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- Pd nanoparticles: an efficient catalyst for the solvent-free synthesis of 2,3-disubstituted-4-thiazolidinones
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Abstract: Palladium nanoparticles (Pd NPs: ~5-nm diameter) catalysed an efficient, solvent-free protocol for the cyclocondensation reaction of the aldehydes, anilines and mercaptoacetic acid has been developed. This method offers a rapid, relatively economical and ecofriendly protocol for the synthesis of 2,3-disubstituted-4-thiazolidinones for the first time. Moreover, the catalyst can also be easily recovered and recycled with no loss of catalytic activity. Graphical Abstract: [Figure not available: see fulltext.]
- Harale, Rajkumar R.,Shitre, Praveen V.,Sathe, Bhaskar R.,Shingare, Murlidhar S.
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p. 6695 - 6703
(2016/07/12)
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- Efficient chemoselective hydrogenation of organic azides catalyzed by palladium nanoparticles with alkyne-derived homogeneous supports
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Catalytic chemoselective hydrogenation of organic azides using palladium nanoparticles stabilized by alkyne derivatives was studied. A broad range of aromatic and aliphatic azides were smoothly reduced to the corresponding amines in excellent yields with a quite small amount of the catalyst. Hydrogenation of 3-phenylpropylazide gave 3-phenylpropylamine almost quantitatively with a substrate-to-palladium molar ratio (S/Pd) of 12,900 under 8?atm of H2. The reaction under 1?atm of H2also proceeded smoothly with an S/Pd of 1000. Several reduction-sensitive functional groups, such as carbonyl, halide, benzylic OH, and aliphatic nitro were well tolerated under the reaction conditions.
- Arai, Noriyoshi,Onodera, Nozomi,Ohkuma, Takeshi
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supporting information
p. 4183 - 4186
(2016/08/24)
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- Palladium pnictide oxides Nd10Pd3As8O10 and Sm10Pd3As8O10-low temperature structural phase transition and physical properties
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New quaternary palladium arsenide oxides Nd10Pd3As8O10 and Sm10Pd3As8O10 were synthesized from the rare earth (RE) elements, appropriate rare earth oxides, arsenic and palladium sponge at maximum annealing temperatures of 1223 K. The structure of the neodymium compound was refined from X-ray single crystal diffractometer data at different temperatures. The samarium compound was found to be isotypic on the basis of Guinier powder diffraction. Both compounds are isotypic with Nd10Au3As8O10 and consist of stacked, formal polycationic [RE10O10]10+ and polyanionic [Pd3(As2)4]10- layers. In contrast to the well-known, tetrahedrally coordinated rare earth oxide layers with basically ionic bonding, the palladium arsenide layers exhibit rather covalent character, which is underlined by XPS data. Electrical resistivity measurements indicate semiconducting properties for Nd10Pd3As8O10 and additionally show an anomaly at approximately 160 K, which results from a structural phase transition, clarified by X-ray single crystal diffractometer data. The phase transition originates from out of plane distortions of the palladium atoms, which show structural order around 160 K. Specific heat measurements and temperature dependent magnetic susceptibility data (including low field measurements) do not show any corresponding anomaly, referring to a very small structural change, which mainly effects electrical conductivity in the present palladium arsenide substructure. Nd10Pd3As8O10 exhibits Curie-Weiss paramagnetism and shows no magnetic order down to 2.5 K. Electronic band structure calculations predict a metallic state-probably due to the very small gap-and confirm the covalent character of the [Pd3As8] layer.
- Bartsch, Timo,Niehaus, Oliver,Hoffmann, Rolf-Dieter,Bartsch, Manfred,Zacharias, Helmut,Johrendt, Dirk,P?ttgen, Rainer
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p. 6727 - 6741
(2016/07/28)
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- (N-Heterocyclic Carbene)2-Pd(0)-Catalyzed Silaboration of Internal and Terminal Alkynes: Scope and Mechanistic Studies
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Pd(ITMe)2(PhC≡CPh) acts as a highly reactive precatalyst in the silaboration of terminal and internal alkynes to yield a number of known and novel 1-silyl-2-boryl alkenes. Unprecedented mild reaction temperatures for terminal alkynes, short reaction times, and low catalytic loadings are reported. During mechanistic studies, cis-Pd(ITMe)2(SiMe2Ph)(Bpin) was directly synthesized by oxidative addition of PhMe2SiBpin to Pd(ITMe)2(PhC≡CPh). This represents a very rare example of a (silyl)(boryl)palladium complex. A plausible catalyst decomposition route was also examined.
- Ansell, Melvyn B.,Spencer, John,Navarro, Oscar
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p. 2192 - 2196
(2016/04/26)
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- (Ferrocenylpyrazolyl)palladium(II) complexes: Syntheses, characterization and rearrangement in solution
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Reactions of L1-L6 (3-ferrocenylpyrazolyle (L1), 3-ferrocenyl-5-methylpyrazolyle (L2) 3-ferrocenylpyrazolyl-methylenepyridine (L3) and 3-ferrocenyl-5-methylpyrazolylmethylene-pyridine (L4), 3-ferrocenylpyrazolylethylamine (L5) and 3-ferrocenyl-5-methylpyrazolylethyl-amine (L6)) with [PdCl(Me) (cod)] formed the mononuclear complexes [PdCl(Me) (κ1-L1)2] (1), [PdCl(Me) (κ1-L2)2] (2), [PdCl(Me) (κ2-L3)] (3), [PdCl(Me) (κ2-L4)] (4), [PdCl(Me) (κ2-L5)] (5) and [PdCl(Me) (κ2-L6)] (6). Reactions of 1-6 with the halide abstractor, Na[BAr4], (Ar = 3,5-(CF3)2C6H3), led to the formation of the salts, [PdMe(NCMe) (κ1-L1)2][BAr4] (7), [PdMe(NCMe) (κ1-L2)2][BAr4] (8), [PdMe(NCMe) (κ2-L3)][BAr4] (9), [PdMe(NCMe) (κ2-L4)][BAr4] (10), [PdMe(NCMe) (κ2-L5)][BAr4] (11), [PdMe(NCMe) (κ2-L6)][BAr4] (12) respectively. However, when 3 or 4 was reacted with of Na[BAr4] and a slight excess of methyl acrylate, the products were surprisingly the bis(ligand)palladium complexes [Pd(κ2-L3)2][BAr4]2 (13) and [Pd(κ2-L4)2][BAr4]2 (14) instead of the expected acylpalladium chelate complexes ([(κ2-L)Pd{(CH2)2C(O)OMe}][BAr4]). Complexes 1-6, activated with Na[BAr4], and pre-activated complexes 7-12 at 10 bar of ethylene and 30 bar of carbon monoxide produced polyketones, albeit with low activity (ca. 1.00 g.mmol-1Pd.h-1); with the active catalysts rearranging to mainly bis(pyrazolyl)palladium complexes similar to 13 and 14.
- Obuah, Collins,Darkwa, James
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- Palladium(II)-Mediated Addition of Benzenediamines to Isocyanides: Generation of Three Types of Diaminocarbene Ligands Depending on the Isomeric Structure of the Nucleophile
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Coupling of the palladium-bis(isocyanide) complexes cis-[PdCl2(CNR)2] (R = 2,6-Me2C6H3 1, 2-Cl-6-MeC6H3 2) with benzene-1,3-diamine (BDA1) leads to the diaminocarbene species cis-[PdCl2(CNR){C(NHR)=NH(1,3-C6H4NH2)}] (5 and 6, respectively). In this reaction, BDA1 behaves as a monofunctional nucleophile that adds to one of the RNC ligands by one amino group. By contrast, the reaction of 1 and 2 with benzene-1,4-diamine (BDA2) involves both amino functionalities of the diamine and leads to the binuclear species [cis-PdCl2(CNR){ΜC(NHR)=NH(1,4-C6H4)NH=C(NHR)}-(cis)-PdCl2(CNR)] (6 and 7) featuring two 1,4-bifunctional diaminocarbene ligands. The reaction of cis-[PdCl2(CNR)2] (R = cyclohexyl 3) with either BDA1 or BDA2 does not afford any isolable carbene derivatives. The most versatile chemistry was observed when 1-3 were treated with benzene-1,2-diamine (BDA3) and the relevant substituted 1,2-diamines, viz., 4,5-dimethylbenzene-1,2-diamine (BDA4) and 4,5-dichlorobenzene-1,2-diamine (BDA5). The addition of these diamines brings about the formation of the monocarbene cationic complexes cis-[PdCl(CNR){C(NHR)=NHC6H2X2NH2}]Cl (X = H, Me, Cl) (8-16), the Chugaev-type C,C-bound bis-carbenes cis-[PdCl2{C(NHR)=NHC6H2X2NH=C(NHR)}] (17, 18), and the bis(C,N-chelated)carbene complexes cis-[Pd{C(NHR)=NHC6H2X2NH2}2]Cl2 (19-24). All prepared complexes (with the exception of 17 and 18) were isolated as colorless or pale yellow solids and characterized by elemental analyses (C, H, N), HRESI±-MS, IR, 1H and 13C{1H} NMR spectroscopies, and 4, 7, 13, 16, and 24 by X-ray diffraction. Complexes 17 and 18 were characterized by HRESI±-MS and IR spectroscopy, and their structures were established by X-ray crystallography.
- Kinzhalov, Mikhail A.,Timofeeva, Svetlana A.,Luzyanin, Konstantin V.,Boyarskiy, Vadim P.,Yakimanskiy, Anton A.,Haukka, Matti,Kukushkin, Vadim Yu.
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p. 218 - 228
(2016/02/05)
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- Oxoanionic noble metal compounds from fuming nitric acid: The palladium examples Pd(NO3)2 and Pd(CH3SO3)2
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The oxidation of elemental palladium at 100?°C in a mixture of fuming nitric acid and a pyridine-SO3 complex leads to the anhydrous nitrate Pd(NO3)2 (monoclinic, P21/n, Z = 2, a = 469.12(3) pm, b = 593.89(3) pm, c = 805.72(4) pm, ?2 = 105.989(3)?°, V = 215.79(2) A??3). The Pd2+ ions are in square-planar coordination with four monodentate nitrate groups which are connected to further palladium atoms, leading to a layer structure. The reaction of elemental palladium with a mixture of fuming nitric acid and methanesulfonic acid at 120?°C leads to single crystals of Pd(CH3SO3)2 (monoclinic, P21/n, Z = 2, a = 480.44(1) pm, b = 1085.53(3) pm, c = 739.78(2) pm, ?2 = 102.785(1)?°, V = 376.254(17) A??3). Also in this structure the Pd2+ ions are in square-planar coordination with four monodentate anions; however, the connection to adjacent palladium atoms leads to a chain-type structure. The thermal decomposition of the compounds has been investigated by means of DSC/TG measurements. Furthermore, IR and Raman spectra have been recorded, and an assignment of the observed vibrational frequencies has been carried out based on theoretical investigations.
- Bruns, J??rn,Kl??ner, Thorsten,Wickleder, Mathias S.
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p. 1294 - 1301
(2015/03/05)
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- Thermal stability of Pd(1,4-bis(2-hydroxyethyl)piperazine)Cl2 and its role in the catalysis of base hydrolysis of α-amino acid esters
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Pd(BHEP)Cl2 was synthesized and characterized (BHEP = 1,4-bis(2-hydroxyethyl)piperazine). The complex decomposes in two steps, leaving a residue of palladium metal. Amino acid ester (L) reacts with [Pd(BHEP)(H2O)2]2+ (BHEP = 1,4-bis(2-hydroxyethyl)piperazine), giving mixed-ligand complexes, [Pd(BHEP)L]2+. The kinetics of hydrolysis of [Pd(BHEP)L]2+ have been studied by pH-stat technique, and rate constants were obtained. Rate acceleration observed for glycine methyl ester is high. The effect with methionine methyl ester is much less marked, as the mixed-ligand complexes with these ligands do not involve alkoxycarbonyl donors. Possible mechanisms for these reactions are considered.
- Shehata, Mohamed R.,Shoukry, Mohamed M.,Shokry, Shokry A.,Mabrouk, Mahmoud A.
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p. 3272 - 3281
(2015/09/22)
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- Fabrication, characterization and electrochemical properties of porous hollow palladium spheres
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In the present study, porous hollow palladium particles with uniform size distribution have been successfully prepared by templating method with silica sphere as template materials. Experimental results show that hydrazine hydrate is a preferable reducing regent to prepare pure palladium layer by electroless plating rather than sodium hypophosphite. Silica sphere templates can be easily removed after eroded in alkali solutions, and then palladium particle with hollow structure and a specific surface area of ~10.26 m2/g can be prepared. Furthermore, electrochemical properties of the porous hollow palladium were also investigated and the results reveal that it has superior ethanol oxidation ability.
- Kong, Qingquan,Liu, Ying,Lian, Lixian,Zhang, Jing,Wang, Li
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p. 701 - 706
(2015/02/19)
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- Binary α-unsaturated palladium carboxylates and their complexes with morpholine derivatives: The Crystal structure of palladium carbamoyl crotonate (OC4H8NH)2Pd[OC4H8N(C=O)](MeCH=CHCO2)·H2O, a product of the first inner-sphere amination reaction of α-unsaturated palladium carbonyl carboxylates with morpholine
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Binary α-unsaturated palladium carboxylates have been synthesized by substitution of α-unsaturated acids RCOOH (R is CH2=C(Me), MeCH=CH, PhCH=CH) for the acetate ion in Pd3(μ-MeCOO)6. These carboxylates react with amines A (A is morpholine (M), methylmorpholine (MM), or thiomorpholine (MS)) to give trans-Pd(A)2(RCOO)2 similar to trans-A2(MeCO2)2. The structures of the trans-Pd(A)2(RCOO)2 complexes (R is MeCH=CH; A is M, MM, MS) have been determined by X-ray crystallography. The effect of solvent on the crystal structure of the complexes has been demonstrated for trans-(MeCH=CHCO2)2Pd(C4H9NO)2 as an example. The amination reaction of palladium carbonyl crotonate with a secondary amine, morpholine, has been studied for the first time. The reaction involves disproportionation of Pd(I) into Pd(0) and Pd(II) and leads to the first unsaturated palladium(II) carbamoyl carboxylate - palladium carbamoyl crotonate trans-(OC4H8NH)2Pd[OC4H8NC(=O)](MeCH=CHCO2)·H2O, as well as to trans-M2Pd(MeCH=CHCO2)2 and (C4H10NO)+(MeCH=CHCO2)-. The structures of these compounds have been proved by X-ray crystallography.
- Efimenko,Ankudinova,Kuz'Mina,Churakov,Ivanova,Demina,Erofeeva
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p. 848 - 860
(2015/07/28)
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- Seedless Growth of Palladium Nanocrystals with Tunable Structures: From Tetrahedra to Nanosheets
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Despite the great success that has been accomplished on the controlled synthesis of Pd nanocrystals with various sizes and morphologies, an efficient approach to systematic production of well-defined Pd nanocrystals without seed-mediated approaches remains a significant challenge. In this work, we have developed an efficient synthetic method to directly produce Pd nanocrystals with a highly controllable feature. Three distinct Pd nanocrystals, namely, Pd nanosheets, Pd concave tetrahedra, and Pd tetrahedra, have been selectively prepared by simply introducing a small amount of ascorbic acid (AA) and/or water without the other synthesis conditions changed. We found that the combined use of AA and water is of importance for the successful production of the unique Pd nanosheets. Detailed catalytic investigations showed that all the obtained Pd nanocrystals exhibit higher activity in the formic acid electrooxidation and styrene hydrogenation with respect to the Pd black, and their activities are highly shape-dependent with Pd nanosheets demonstrating a higher activity than both the Pd concave tetrahedra and Pd tetrahedra, which is likely due to the simple yet important feature of ultrathin thickness of Pd nanosheets. The present work highlights the importance of structures in tuning the related properties of metallic nanocrystals.
- Zhang, Ying,Wang, Mingsong,Zhu, Enbo,Zheng, Yuebing,Huang, Yu,Huang, Xiaoqing
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p. 7519 - 7525
(2015/11/23)
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- The facet-dependent enhanced catalytic activity of Pd nanocrystals
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A systematic study of heterogeneous Buchwald-Hartwig amination using shape-controlled Pd nanocrystals with distinctly different surface facets is presented. This journal is the Partner Organisations 2014.
- Kim, Minjune,Kim, Yeonjoon,Hong, Jong Wook,Ahn, Seihwan,Kim, Woo Youn,Han, Sang Woo
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supporting information
p. 9454 - 9457
(2014/08/18)
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- Melamine and melamine-formaldehyde polymers as ligands for palladium and application to Suzuki-Miyaura cross-coupling reactions in sustainable solvents
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The Suzuki-Miyaura cross-coupling reaction is a foundation stone of modern organic synthesis, as evidenced by its widespread use in the preparation of pharmaceuticals, agrochemicals, polymers, and other functional materials. With the prevalence of this venerable reaction in industrial synthesis, it is prudent to ensure its application adheres to the tenets of green chemistry. The introduction of cross-coupling catalysts that are active in sustainable solvents is therefore an important endeavor. In this report, a melamine-palladium complex is introduced as a versatile catalyst for the Suzuki-Miyaura cross-coupling reaction. This catalyst is soluble and active in both water and the renewable organic solvent ethyl lactate. The melamine-palladium catalyst can also be cross-linked by reaction with formaldehyde to generate an insoluble polymeric catalyst that can be recovered after the cross-coupling. The melamine-palladium system is inexpensive, easy to handle, bench-stable, and effective in catalysis in the presence of a variety of impurities (high cross-coupling yields were obtained in reactions run in unfiltered river water to illustrate this final point). Additionally, investigations reported herein revealed an intriguing relationship between catalytic efficiency and the base employed in the cross-coupling reaction. Implications for the mechanism of transmetalation in aqueous Suzuki-Miyaura cross-coupling reaction are discussed.
- Edwards, Grant A.,Trafford, Mitchell A.,Hamilton, Alaina E.,Buxton, Audrey M.,Bardeaux, Matthew C.,Chalker, Justin M.
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supporting information
p. 2094 - 2104
(2014/04/03)
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- Determination of the loading and stability of Pd in an arborescent copolymer in ethanol by microplasma-optical emission spectrometry
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We report, for the first time, the utilization of a microplasma-optical emission spectrometry system for the determination, without sample digestion, of the concentration of Pd loaded in a dendritic graft (arborescent) copolymer dissolved in ethanol. The preparation of polymer-stabilized colloidal Pd particles was achieved by adding palladium acetate to a solution of the copolymer, viz. arborescent polystyrene-graft-poly(2-vinylpyridine), in ethanol. No acid digestion was needed prior to the analysis, and only micro-amounts (μL) of sample were required. Calibration curves obtained for Pd in ethanol were linear in the concentration range of interest, and the percent relative standard deviation (%RSD) ranged from 7.4 to 0.1%. The Pd detection limit was 28 pg (absolute) or 3 ng mL-1 (when using 10 μL samples). The average Pd loading per mole of 2-vinylpyridine unit was determined to be 99.5 mol%. The kinetics of aggregation of the metallic species to Pd black were also determined. The Pd concentration in ethanol without polymer was found to abate to about one third of its initial value after 5 days. In the presence of the copolymer, however, the concentration of Pd in solution remained constant for at least 10 days. The low electric power and gas consumption of the microplasma device, its low operating cost and detection limit, compatibility with organic solvents, and the small sample amount required make this system a greener and cheaper alternative to the inductively coupled plasma (ICP) spectrometry commonly used for Pd quantification.
- Nguon, Olivier,Gauthier, Mario,Karanassios, Vassili
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p. 8978 - 8984
(2014/03/21)
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- Facile synthesis of iridium nanocrystals with well-controlled facets using seed-mediated growth
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Iridium nanoparticles have only been reported with roughly spherical shapes and sizes of 1-5 nm, making it impossible to investigate their facet-dependent catalytic properties. Here we report for the first time a simple method based on seed-mediated growth for the facile synthesis of Ir nanocrystals with well-controlled facets. The essence of this approach is to coat an ultrathin conformal shell of Ir on a Pd seed with a well-defined shape at a relatively high temperature to ensure fast surface diffusion. In this way, the facets on the initial Pd seed are faithfully replicated in the resultant Pd@Ir core-shell nanocrystal. With 6 nm Pd cubes and octahedra encased by {100} and {111} facets, respectively, as the seeds, we have successfully generated Pd@Ir cubes and octahedra covered by Ir{100} and Ir{111} facets. The Pd@Ir cubes showed higher H2 selectivity (31.8% vs 8.9%) toward the decomposition of hydrazine compared with Pd@Ir octahedra with roughly the same size.
- Xia, Xiaohu,Figueroa-Cosme, Legna,Tao, Jing,Peng, Hsin-Chieh,Niu, Guangda,Zhu, Yimei,Xia, Younan
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supporting information
p. 10878 - 10881
(2014/08/18)
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- Synthesis of Pd particles with various shapes by ionic liquids for HFP hydrogenation catalyst
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Palladium particles were simply synthesized using various ionic liquids. The morphology of the particles was significantly affected by the anion parts of the ionic liquids. Among the ionic liquids, hexafluorophosphate as an anion part was more effective in forming the palladium particles with relatively small and narrow size distribution. However, irregularly shaped palladium particles were synthesized without ionic liquid assistance. For a hexafluoropropylene hydrogenation to produce hydrofluorocarbons, palladium was impregnated on a carbon powder as a catalyst. During the preparation of the catalyst, ionic liquids were added to control the shape of the palladium on the support. After calcinations at 500 °C, all catalysts possessed the comparable crystal structure. Under identical reaction conditions, the catalyst prepared using 1-hexyl-3-methylimidazolium hexafluorophosphate was the most effective in this reaction. Hence, catalytic activity was mainly determined by the size of the palladium particles.
- Kim, Chang Soo,Yoo, Kye Sang
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p. 2471 - 2476
(2014/11/08)
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- NMR Studies of the Species Present in Cross-Coupling Catalysis Systems Involving Pd(η3-1-Ph-C3H4) (η5-C5H5).
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The compounds Pd(η3-1-Ph-C3H4) (η5-C5H5) (I), Pd2(dba) 3 (II), Pd(OAc)2 (III), and [Pd(η3-1-Ph- C3H4)Cl]2 (IV) are frequently utilized as catalyst precursors for a variety of cross-coupling processes, including Suzuki-Miyaura, Heck-Mizoroki, Sonogashira, and Buchwald-Hartwig reactions. In the preceding paper in this issue, we assess and compare catalyst systems based on I-IV activated with PBut3, XPhos, and/or Mor-Dalphos for the prototypical Buchwald-Hartwig amination reactions of 4-bromo- and 4-chloroanisole with morpholine, noting several apparent incongruities which seem to indicate mechanistic dissimilarities for various reactant/precatalyst combinations. In this paper we investigate by NMR spectroscopy the solution chemistry of I and IV with PBut3, XPhos, and Mor-Dalphos, noting similarities and differences in the respective abilities of these precursor-ligand combinations to generate palladium(0) catalyst systems. We find inter alia that steric requirements prevent Xphos and Mor-Dalphos from forming 2:1 palladium(0) complexes and, surprisingly, that 1:1 palladium(0) complexes of Xphos and Mor-Dalphos are unstable with respect to dissociation to free ligand and palladium metal. In other words, these two ligands and, by implication, other sterically demanding phosphine ligands do not form palladium(0) compounds.
- Borjian, Sogol,Baird, Michael C.
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p. 3936 - 3940
(2014/11/26)
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