Activity Of PdCl2 Research Articles

Mechanochemical Synthesis of PdO2 Nanoparticles Immobilized over Silica Gel for Catalytic Suzuki-Miyaura Cross-Coupling Reactions Leading to the C-3 Modification of 1H-Indazole with Phenylboronic Acids.

The C-3 modification of 1H-indazole has produced active pharmaceuticals for the treatment of cancer and HIV. But, so far, this transformation has seemed less available, due to the lack of efficient C-C bond formation at the less reactive C-3 position. In this work, a series of silica gel-supported PdO2 nanoparticles of 25-66 nm size were prepared by ball milling silica gel with divalent palladium precursors, and then employed as catalysts for the Suzuki-Miyaura cross-coupling of 1H-indazole derivative with phenylboronic acid. All the synthesized catalysts showed much higher cross-coupling yields than their palladium precursors, and could also be reused three times without losing high activity and selectivity in a toluene/water/ethanol mixed solvent. Although the palladium precursors showed an order of activity of PdCl2(dppf, 1,1'-bis(diphenylphosphino)ferrocene) > PdCl2(dtbpf, 1,1'-bis(di-tert-butylphosphino)ferrocene) > Pd(OAc, acetate)2, the synthesized catalysts showed an order of C1 (from Pd(OAc)2) > C3 (from PdCl2(dtbpf)) > C2 (from PdCl2(dppf)), which conformed to the orders of BET (Brunauer-Emmett-Teller) surface areas and acidities of these catalysts. Notably, the most inexpensive Pd(OAc)2 can be used as a palladium precursor for the synthesis of the best catalyst through simple ball milling. This work provides a highly active and inexpensive series of catalysts for C-3 modification of 1H-indazole, which are significant for the large-scale production of 1H-indazole-based pharmaceuticals.

Role of various pretreatment processes in electroless nickel deposition on TiH2 particles with a simple plating bath

Electroless nickel was successfully deposited on TiH2 particles with a simple plating bath which contains only a nickel salt NiCl2 and a strong reductant dimethylamine borane (DMAB) and the effect of various pretreatment processes was studied. The three different pretreatment processes include: (1) a two-step pretreatment with SnCl2 sensitization followed by PdCl2 activation (SnCl2–PdCl2); (2) only PdCl2 activation, and (3) without pretreatment (direct electroless deposition). The characteristics of TiH2 powders before and after nickel deposition were analyzed with field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). It was found that except for the traditional SnCl2–PdCl2 pretreatment process, the pretreatment with only PdCl2 activation and direct electroless nickel deposition without any pretreatment of the powder surface can both lead to continuous and homogeneous nickel layer on TiH2 powders. This may be due to the strongly negatively charged powder surface with its very low isoelectric point (I.E.P.) which promotes the adsorption of Ni2+ from the plating bath onto powder surface. On the other hand, the strong reducing agent DMAB facilitate the reduction of Ni2+ ions even without Pd catalysation. This work provides a simplified and alternative way for electroless nickel coating on TiH2 powders with the application in aluminium foaming.

Facile electroless copper plating on diamond particles without conventional sensitization and activation

Conventional electroless plating of copper on diamond particles needs SnCl2 sensitization and PdCl2 activation pretreatments, which needs noble metal and consumes a large amount of reducing agent. In this paper, metallic tungsten coatings were first plated onto diamond particles by microwave-heating salt-bath plating (MHSBP) method, and then copper layer was directly plated onto the out surface of the tungsten layer by an electroless plating method with no need of SnCl2 sensitization and PdCl2 activation pretreatments. Composition and morphology of the coatings was analyzed by XRD, SEM, and EDS. The results show that the copper coating on the diamond surfaces can be adjusted by control the concentration of CuSO4·5H2O and plating temperature, and a full copper coating is achieved with content of CuSO4·5H2O of 19.6 g/L in the plating solution at 60 °C. The bending strength of the coated diamond/Cu composites is as high as 630 MPa, which increases 93.3% than the uncoated composites. This work presents an electroless plating of copper can directly on the surfaces of diamond particles with no need of conventional sensitization and activation, and a strong interface combination between coated diamond and copper.

Fabrication of Nickel Coating on Polyethylene Terephthalate Substrate Modified with Primer: Effect of Surface Roughness on Structural Properties of Plated Coating

Fabrication of nickel coating on polyethylene terephthalate substrate via primer modification combined with PdCl2 activation and electroless nickel plating is researched. The effect of surface roughness on structural properties of the plated coating was investigated. The modified substrate could adsorb Sn2+ and Pd2+, which can catalyze the electroless nickel plating. Increasing the SiO2 content in the primer could enhance surface roughness of primer coating, adsorbed capacity of Sn2+ and Pd2+, crystallinity and adhesive force of nickel-plated coating. The nickel-plated film was compact, as SiO2 particles were uniformly dispersed and well bonded with nickel coating. When the average roughness was about 18 μm, the plated coating presented thickness of 2 μm, a low resistivity of 6.6 × 10−5 Ω cm and good adhesive strength of 5B. In addition, selective and flexible nickel patterns could be obtained successfully after laser etching.

Electroless copper plating on nano-silver activated glass substrate: A single-step activation

The electroless copper plating on non-conductive glass substrates by nano-silver activation was studied instead of the conventional two-stepped pre-treatment processes (SnCl2 sensitization and PdCl2 activation). The glass substrate was prepared by polishing with 400 grit silicon carbide abrasive paper and then activated by dipping into Ag(I)-benzoxanine solution to obtain the dispersed nano-silver particles on the surface. The results from SEM, XRD, XRF and TEM illustrated that nano-metallic Ag was successfully prepared and coated on glass substrate. The nano-silver activated glass substrates were then used to study the following parameters: plating time, temperature and concentration of additive gelatin. According to SEM and AFM observation, the Cu film was uniformly grown, smooth and dense of particles. The crystallized sizes of silver and copper on the substrate were calculated by Scherrer's equation, and found to be 45 and 85nm, respectively. In addition, the adhesion of the deposited copper was conducted by using the tape-test technique according to ASTM D3359-02.

Significance of sensitization process in electroless deposition of Ni on nanosized Al2O3 powders

The electroless deposition of Ni on nanosized α-Al2O3 powders of about 150nm diameter has been studied by employing SnCl2 sensitization and PdCl2 activation approach. The bath for electroless deposition was prepared by using NiCl2·6H2O, C6H5NaO7·H2O, NH4Cl and NaH2PO2·H2O, and the deposition was carried out at a bath temperature of 70°C with a pH value of 8.5. The morphology, microstructure and phase structure of Ni-coated α-Al2O3 nanopowders were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD), respectively. It is found that, the sensitization process followed by repetitive resining greatly affects the morphology of Ni deposited in the form of nanoparticles onto the ultrafine alumina particles, different from the conventional continuous electroless film/coating deposited on coarser particles. The resining of the SnCl2 sensitized ultrafine α-Al2O3 particles prior to PdCl2 activation process leads to varied amount of deposited Ni particles with diameters of 50–80nm on the Al2O3. It is revealed that, subsequent reduction process (activation) from Pd2+ to Pd is linked to the original sites of Sn2+ by simultaneous oxidation process from Sn2+ to Sn4+ on the previously sensitized α-Al2O3 nanopowders. Consequently, the form of deposited Ni correlated closely to the surface distribution of reduced Pd which may be continuous or discrete determined predominantly by the density of adsorbed Sn2+ on the powders during sensitization process. It demonstrates a possibility of depositing different distribution structures of metals on nanosized α-Al2O3 powders through controlling SnCl2 sensitization process.

Activation Free SAM-Assisted Silver Electroless Metallization of Textile for Strain Sensor Application

Flexible, stretchable and wearable electronic devices are becoming moredemanding due to their facile interaction with human body. These devices can beeasily mount on clothing or directly attached onto skin. Among wearableelectronic devices, highly stretchable and sensitive strain sensors have drawn lotsof attention for monitoring human body motions. There are number ofrequirements for a high performance strain sensor including high sensitivity (i.e.,gauge factor (GF)), high stretchability, fast response, high stability and lowfabrication cost. Personal health monitoring, sport performance monitoring andhuman motion capturing for entertainment systems are the most popularapplications for a high performance strain senor.In this paper, we present a cost effective simple strain sensor fabricated throughsilver electroless metallization of commercial polyester fabric. To avoid usingSnCl2 or PdCl2 activation solutions, a silica-like layer was formed on polyesterfabric using an acetone based aminopropyltrimethoxysilane (APTMS) solutionfollowed by UV irradiation. Once the anchoring sites for later silanization weredeveloped, a toluene based solution of (3-Mercaptopropyl)trimethoxysilane(MPTMS) were used to activate the polyester fabric. Silver electrolessmetallization was carried out on activated polyester using silver nitrate salt andglucose as reducing agent. Scanning electron microscopy (SEM) and X-raydiffraction spectroscopy (XRD) were used to characterize the Ag-coated polyester.A thin silver coating (<1 μm) with uniform morphology and high purity wasdeposited on polyester. The conductive fabric was cut into strips of 5mmthickness for stretch-conductivity measurements. A micro-tensile machine withan in-situ confocal microscope was coupled with a digital multimeter (2-pointprobing) to investigate strain dependence electrical resistivity. In-situ confocalimaging was used to investigate the micromechanical mechanisms responsible forchanges in resistivity during stretching. A linear decrease in electrical resistancewas detected by stetching untill it reaches to a platu. The results of stretch–conductivitymeasurements suggest the potential application of Ag/Polyester forstrain sensors. Figure 1

Tuning of the catalytic properties of PdCl2(XnPy)2 complexes by variation of the basicity of aromatic ligands

The position and number of substituents in pyridine ligands (XnPy) were correlated with structural, physical, and chemical properties of PdCl2(XnPy)2 complexes applied as catalysts for the carbonylation of aromatic nitrocompounds (phosgene-free method of carbamates production). Thermal stability and catalytic activity of PdCl2(XnPy)2 complexes without steric hindrance increases with increasing XnPy's basicity whereas a decrease of thermal stability and catalytic activity of the complexes is observed for sterically crowded complexes (with the ortho-substituted XnPy). The complexes with X=Cl in meta- position of XnPy decompose to a mixture of PdCl2 and metallic Pd (similarly to complexes with MenPy) whereas complexes with ortho-chlorine (in XnPy) decompose to the organopalladium products. Therefore, two different mechanisms of thermal decomposition are proposed for PdCl2(ClnPy)2 and PdCl2(MenPy)2. The results of complex thermal and structural analysis of a series of PdCl2(XnPy)2 complexes allow us to get insight into the mechanism of nitrobenzene (NB) carbonylation catalyzed by PdCl2(XnPy)2 at 150–180°C. We conclude that the electron transfer from Pd(0) to nitrobenzene is the rate determining step of catalytic cycle of NB carbonylation.

Reflective and conductive surface‐silvered polyimide films prepared by surface graft copolymerization and electroless plating

AbstractArgon plasma‐pretreated polyimide (PI) films were subjected to UV‐induced surface graft copolymerization with 4‐vinylpyridine(4VP) under atmospheric conditions. Electroless plating of silver was carried out effectively on the 4VP graft copolymerized PI (PI‐g‐P4VP) surface after PdCl2 activation and in the absence of SnCl2 sensitization (the Sn‐free process). The surface compositions of the modified PI films were studied by X‐ray photoelectron spectroscopy (XPS). XPS results showed that the PI‐g‐P4VP surface is ready for electroless deposition of silver via the Sn‐free process. The grafted 4VP layer with well‐preserved pyridine groups was used not only as the chemisorption sites for the palladium complexes (without the need for prior sensitization by SnCl2) during the electroless plating of silver, but also as an adhesion promotion layer for the electrolessly deposited silver. The silver metallized PI films show high reflectivity and conductivity with a surface resistance of 1.5 Ω and a reflectivity of 91.3%, respectively. Copyright © 2007 John Wiley &amp; Sons, Ltd.

The role of Pd colloids as catalysts in the phosphane-free methoxycarbonylation of iodobenzene

The catalytic activity of PdCl2(cod) (1) in the methoxycarbonylation of iodobenzene (at 40–70 °C, 1–5 atm of CO, in methanol solution) increased remarkably when tetra-n-butylammonium salts [nBu4N]X (X = Br, Cl, I, BF4, PF6) were added to the system. XRD analyses confirmed that under methoxycarbonylation reaction conditions palladium was reduced to a Pd colloid of nanometer size, 2.0–5.6 nm, which was responsible for the catalytic activity. In the absence of ammonium salts fast deactivation of the colloid was observed, even when PVP (polyvinylpyrrolidone) was added as a stabilizer. Catalytic tests performed with isolated Pd colloid demonstrated its high catalytic activity in methoxycarbonylation when used together with [nBu4N]X salts. A mechanism of palladium reduction to Pd nanoparticles is proposed.

A New Approach on the Active Treatment for Electroless Copper Plating on Glass

AbstractA new method is described for the electroless deposition of copper onto glass. Commercially available glass slide was modified with μ‐amimopropyltrimethoxysilane to form self‐assembled monolayer (SAM) on it. Then it was dipped directly into PdCl2 solution instead of the conventional SnCl2 sensitization followed by PdCl2 activation. Experimental results showed that the Pd2+ ions from PdCl2 solution were coordinated to the ammo groups on the glass surface resulting in the formation of N—Pd complex. In an electroless copper bath containing a formaldehyde reducing agent, the N—Pd complexes were reduced to Pd0 atoms, which then acted as catalysts and initiated the deposition of copper metal. Although the copper deposition rate on SAM‐modified glass was slow at the beginning, it reached to that of conventional method in about 5 min.

Electroless Deposition of Copper on Poly(tetrafluoroethylene) Films Modified by Plasma-Induced Surface Grafting of Poly(4-vinylpyridine)

Argon plasma-pretreated poly(tetrafluoroethylene) (PTFE) films were solution coated with a thin layer of poly(4-vinyl pyridine) (P4VP). Subsequent exposure of the films to argon plasma resulted in the grafting of P4VP on the PTFE films. Electroless plating of copper could be carried out effectively on the P4VP-grafted PTFE (P4VP-g-PTFE) surface after PdCl2 activation and in the absence of SnCl2 sensitization (the Sn-free process). The catalytic processes of the electroless plating of copper in the presence and absence of sensitization by SnCl2 were also compared. The effect of glow discharge conditions on the P4VP concentration and the adhesion strength of the electrolessly deposited copper was investigated. The T-peel adhesion strength of the electrolessly deposited copper with the graft-modified PTFE film was improved in the absence of SnCl2 sensitization and could reach about 3 N/cm. PdCl2 activation and electroless deposition of copper could not be carried out on the pristine or the Ar plasma-treated PTFE surface in the absence of prior sensitization by SnCl2. X-ray photoelectron spectroscopic (XPS) analysis revealed that the electrolessly deposited copper delaminated from the P4VP-g-PTFE film by cohesive failure inside the PTFE film.

Surface Graft Copolymerization of Poly(tetrafluoroethylene) Films with N-Containing Vinyl Monomers for the Electroless Plating of Copper

Argon plasma-pretreated poly(tetrafluoroethylene) (PTFE) films were subjected to UV-induced surface graft copolymerization, under atmospheric conditions, with several N-containing vinyl monomers, including 4-vinylpyridine (4VP), 2-vinylpyridine (2VP), 1-vinylimidazole (VIDz), 1-vinylpyridinone (VPD), and acrylamide (AAm). Electroless plating of copper could be carried out effectively on the 4VP or 2VP graft-copolymerized PTFE surface after PdCl2 activation and in the absence of SnCl2 sensitization. The surface compositions of the modified PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The catalytic processes for the electroless plating of copper in the presence and absence of sensitization by SnCl2 were compared. The adhesion strength of the electrolessly deposited copper on the graft-modified PTFE surface was affected by the type of the monomers used for graft copolymerization, the graft concentration, and the activation time of the PTFE surface in PdCl2 solution. The T-peel adhesion strength between the electrolessly deposited copper and the graft-modified PTFE film was further improved in the absence of the SnCl2 sensitization step and could reach as high as 7 N/cm. However, the electroless deposition of copper could not be carried out on the pristine or Ar plasma-treated PTFE surface in the absence of SnCl2 sensitization.

Synthesis of aromatic diisocyanates by carbonylation of dinitro compounds with carbon monoxide on palladium catalysts

1. The catalytic activity of PdCl2 in the synthesis of aromatic diisocyanates by carbonylation of dinitro compounds depends on the presence of an organic base (pyridine) and a transition-metal oxide in the reaction system, and on the temperature and pressure. 2. The oxides V2O5 and MoO3 activate the PdCl2-pyridine catalyst, the oxides of Sc, Cr, Mn, and Ni reduce the yield of diisocyanates, and Co3O4, and CuO inhibit their formation. 3. The yield of aromatic diisocyanates in the presence of Pd catalysts increases with increasing CO pressure and passes through a maximum at 190–200°C.

The effect of pyridine bases and transition-metal oxides on the activity of PdCl2 in the carbonylation of aromatic mononitro compounds by carbon monoxide

Palladium chloride which is a catalyst for the preparation of phenylisocyanates by the carbonylation of nitro compounds is promoted by pyridine and its homologs and also by transition-metal oxides, which provide for the conversion of nitro compounds into phenyl-, methylphenyl-, and chlorophenylisocyanates in 75–92% yield and 84–97% selectivity at 200°C and 50–100 atm CO.

Influence of molybdenum and iron oxides on the activity of pdcl2 in the carbonylation of 2,4-dinitrotoluene with carbon monoxide

Addition of molybdenum or iron oxides to PdCl2 increases its catalytic activity in the carbonylation of 2,4-dinitrotoluene by carbon monoxide. Increased pressure increases the yield of 2,4-diisocyanatotoluene to ∼90%.

Effect of organic additives on activity of PdCl2, in synthesis of phenyl isocyanate by carbonylation of nitrobenzene

The activity of PdCl2 as a catalyst for the carbonylation of nitrobenzene to phenyl isocyanate at 190° and an initial CO pressure of 100 atm increases by 6–9 times when either pyridine or quinoline is added to the reaction system.