A mild and efficient palladium–triethylsilane system for reduction of olefins and carbon–carbon double bond isomerization

The versatility of palladium(II) acetate and palladium on activated charcoal catalysts with triethylsilane has been investigated in the hydrogenation and the isomerization of carbon–carbon double bond of 1‐alkenes. The reduction of 1‐alkenes was carried out in the presence of triethylsilane, ethanol and a catalytic amount of palladium(II) acetate or palladium on activated charcoal, at room temperature. This facile and efficient method affords high yields for hydrogenation of unsaturated alkenes to the corresponding alkanes. Then the carbon–carbon double bond isomerization of 1‐alkenes was tested using the same catalysts in the absence of solvent. The system palladium(II) acetate‐triethylsilane was found to be more effective compared with palladium on an activated charcoal–triethylsilane system at room temperature, while comparable results were obtained at 50 °C for both catalysts. Copyright © 2006 John Wiley & Sons, Ltd.     

The application of infrared spectroscopy to probe the surface morphology of alumina-supported palladium catalysts

Five alumina-supported palladium catalysts have been prepared from a range of precursor compounds [palladium(II) nitrate, palladium(II) chloride, palladium(II) acetylacetonate, and tetraamminepalladium(II) tetraazidopalladate(II)] and at different metal loadings (1-7.3 wt %). Collectively, this series of catalysts provides a range of metal particle sizes (1.2-8.5 nm) that emphasize different morphological aspects of the palladium crystallites. The infrared spectra of chemisorbed CO applied under pulse-flow conditions reveal distinct groupings between metal crystallites dominated by low index planes and those that feature predominantly corner/edge atoms. Temperature-programmed infrared spectroscopy establishes that the linear CO band can be resolved into contributions from corner atoms and a combination of (111)(111) and (111)(100) particle edges. Propene hydrogenation has been used as a preliminary assessment of catalytic performance for the 1 wt % loaded catalysts, with the relative inactivity of the catalyst prepared from palladium(II) chloride attributed to a diminished hydrogen supply due to decoration of edge sites by chlorine originating from the preparative process. It is anticipated that refinements linking the vibrational spectrum of a probe molecule with surface structure and accessible adsorption sites for such a versatile catalytic substrate provide a platform against which structure/reactivity relationships can be usefully developed.     

Synthesis and catalytic application of Pd complex catalysts: Atom‐efficient cross‐coupling of triarylbismuthines with haloarenes and acid chlorides under mild conditions

Palladium‐catalysed cross‐coupling reactions are some of the most frequently used synthetic tools for the construction of new carbon–carbon bonds in organic synthesis. In the work presented, Pd(II) complex catalysts were synthesized from palladium chloride and nitrogen donor ligands as the precursors. Infrared and ¹H NMR spectroscopic analyses showed that the palladium complexes were formed in the bidentate mode to the palladium centre. The resultant Pd(II) complexes were tested as catalysts for the coupling of organobismuth(III) compounds with aryl and acid halides leading to excellent yields with high turnover frequency values. The catalysts were stable under the reaction conditions and no degradation was noticed even at 150°C for one of the catalysts. The reaction proceeds via an aryl palladium complex formed by transmetallation reaction between catalyst and Ar₃Bi. The whole synthetic transformation has high atom economy as all three aryl groups attached to bismuth are efficiently transferred to the electrophilic partner.     

Solid-supported cross-coupling catalysts derived from homogeneous nickel and palladium coordination complexes

Solid-supported catalysts derived from homogeneous nickel(II) and palladium(II) non-symmetrical salen-type coordination complexes have been prepared and shown to be effective in the heterogeneous catalysis of carbon-carbon cross-coupling reactions. The nickel catalyst has been used in room-temperature Tamao-Kumada-Corriu reactions and the palladium catalyst in the Heck reaction at elevated temperatures. The complexes were prepared by improved methods and characterised by spectroscopic techniques. Comparisons between the solid-supported catalysts and their homogeneous analogues are reported. The single-crystal structure determination of the nickel and palladium complexes [M(salenac-OH)][M = Ni, Pd; salenac-OH = 9-(2',4'-dihydroxyphenyl)-5,8-diaza-4-methylnona-2,4,8-trienato](2-)] is reported.     

Norbornene/n‐Butyl methacrylate copolymerization over α‐Diimine nickel and palladium catalysts supported on multiwalled carbon nanotubes

The covalently immobilized multiwalled carbon nanotubes (MWNTs) supported three‐dimensional geometry α‐diimine nickel, palladium catalysts are prepared by corresponding α‐diimine nickel, palladium complexes and activated MWNTs. The molecular structures of the catalysts have been confirmed by X‐ray single‐crystal analyses, NMR and XPS, as well as elemental analysis. Compared with nickel, palladium catalysts without modification and physical mixing of nickel, palladium catalysts with MWNTs, the MWNTs supported nickel, palladium catalysts show improved activity and productivity in norbornene homopolymerization and copolymerization with polar monomer. The morphology of the resulting polymers obtained from MWNTs‐supported nickel(II) complex reveals that the MWNTs are dispersed uniformly in polymer and wrapped by polymers to squeeze out of spherical particles, leading to the enhanced processability and mechanical properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3213–3220     

Ruthenium(III) Catalyzed Oxidation Of Ethylenediaminetetraacetic Acid By N-Bromosuccinimide In Aqueous Alkaline Medium – A Kinetic And Mechanistic Study

The formation mechanism of microheterogeneous hydrogenation catalysts based on phosphinepalladium (II) complexes has been considered. According to elemental analysis, X-ray diffraction, electron microscopy, NMR, and IR spectroscopy, the catalyst is a nanoscale palladium organophosphorus matrix and (or) palladium phosphide with immobilized palladium clusters. This revised version was published online in June 2006 with corrections to the Cover Date.     

Complexometric determination of palladium(II) using thioacetamide as a selective masking agent

A simple, rapid and accurate complexometric method for the determination of palladium(II) is proposed, based on the selective masking property of thioacetamide towards palladium(II). In the presence of diverse metal ions, palladium(II) is complexed with excess of EDTA and the surplus EDTA is back titrated at pH 5-5.5 (acetic acid-sodium acetate buffer) with standard lead nitrate solution using xylenol orange as indicator. An excess of a 0.5% aqueous solution of thioacetamide is then added to displace EDTA from Pd(II)-EDTA complex. The released EDTA is titrated with the same standard lead nitrate solution as before. Reproducible and accurate results are obtained in the concentration range 0.5 mg - 17.80 mg of palladium with relative error of +/- 0.16% and coefficient of variation not exceeding 0.26%. The effect of diverse ions is studied. The method is used for the determination of palladium in its complexes, catalysts and synthetic alloy mixtures.     

Ligand-modulated palladium oxidation catalysis: mechanistic insights into aerobic alcohol oxidation with the Pd(OAc)(2)/pyridine catalyst system

Pd(OAc)(2):pyridine (1:4) is an efficient catalyst system for the oxidation of alcohols with molecular oxygen. A mechanistic study of this reaction reveals that pyridine promotes the aerobic oxidation of palladium(0) but inhibits the oxidation of alcohol by palladium(II). Kinetic results reveal that turnover-limiting substrate oxidation consists of (i) formation of a palladium(II)-alkoxide, (ii) pyridine dissociation, and (iii) beta-hydride elimination. These results provide a framework for the design and/or screening of more effective aerobic oxidation catalysts.     

Flow-Injection Study and Analytical Applications of the Reactions of Palladium(II) and Platinum(IV) with Tin(II) Chloride in Hydrochloric Acid Solutions

The interaction of palladium(II) and platinum(II) with tin(II) chloride in hydrochloric acid solutions was studied by flow-injection (FI) spectrophotometry. It was found using kinetic measurements in the stopped flow mode that the composition of detected products and the rate of their formation depend on the concentrations of tin(II) and chloride ions in the reaction zone and on the acidity of the solution. Optimal FI conditions were found, and the selectivity of interaction of palladium(II) with tin(II) chloride was estimated for the detection of the signal at 407 nm (yellow form) and 646 nm (green form). It was demonstrated that the reaction of the formation of yellow platinum(IV) complexes is slower than that for palladium(II), especially at rather low concentrations of hydrochloric acid in the reaction flow. Based on the detection of green complexes of palladium(II) with tin(II) chloride, a flow injection method was proposed for the selective spectrophotometric determination of palladium(II) in the presence of other platinum-group metals. The height of the recorded peak is directly proportional to the concentration of palladium(II) in the injected solution in the range of 0.028–0.300 mM. The method was used for the analysis of pharmaceuticals and industrial catalysts.     

Propiconazole and Penconazole as Effective Extractants for Selective recovery and concentration of platinum(IV) and palladium(II) from hydrochloric acid solutions formed in leaching of spent aluminoplatinum and aluminopalladium catalysts

Selective recovery and concentration of platinum(IV) and palladium(II) from hydrochloric acid solutions of varied composition was studied using commercial reagents propiconazole and penconazole as extractants. The ranges of hydrochloric acid concentrations for effective extraction and highly selective separation of platinum metals from Al(III) and Ni(II) with propiconazole (toluene with 15 vol % n-decanol as deluent) and penconazole (chloroform) were determined. The conditions for 10-fold selective concentration of platinum metals with recovery of more than 99.9% of metal ions into the organic phase were found. The conditions for quantitative (>99%) stripping of platinum(IV) with a hydrochloric acid solution of thiourea and palladium(II) with ammonia solution were determined. The results obtained can be used for optimizing the modes of selective recovery of platinum(IV) and palladium(II) from hydrochloric acid solutions formed in leaching of alumina-supported platinum-rhenium, platinum-nickel, and palladium catalysts.     

Cationic palladium(II) catalysts on O-carboxymethyl chitosan Schiff base for Suzuki coupling reactions

In this study, catalytic activity of two different cationic O-Carboxymethyl chitosan Schiff base palladium (II) complexes in Suzuki coupling reactions and synthesis of biarlys having different functional groups, and reusability of the catalysts were tested. Chemical structures of the synthesized biaryls were elucidated by GC-MS and ¹H-NMR; and no by-products were observed in the spectra. Cationic palladium (II) catalysts high turnover numbers and selectivity were recorded for the reactions. Mercury test demonstrated that the reaction mechanism proceed a homogeneous route. Reusability tests of cationic biocatalysts showed that their catalytic activity were still highly efficient even after six cycles.     

Preparation of palladium clusters protected by silica-supported,crosslinking, partially phosphorylated poly(vinyl alcohol) and their catalytic activity

The palladium cluster protected by silica-supported, crosslinking, partially phosphorylated poly(vinyl alcohol) (P-PVA) was prepared from a crosslinking P-PVA–Pd(II) complex by reduction in alcohol. The P-PVA–Pd complex and the palladium cluster protected by P-PVA were analyzed by electron spectroscopy, X-ray photoelectron spectrometry and transmission electron microscopy. The complex formation between the Pd(II) ion and phosphoric acid groups in P-PVA was important in the formation of a fine palladium cluster. Palladium clusters protected by silica-supported crosslinking P-PVA were used as catalysts for the hydrogenation of nitrobenzene or acrylic acid at 30°C under atmospheric pressure. The palladium cluster protected by crosslinking P-PVA supported on silica was the most active catalyst, was stable and had no by-products, compared with the palladium cluster protected by silica-supported noncrosslinking P-PVA or PVA.     

Solid-Phase Synthesis and Encoding Strategies for Olefin Polymerization Catalyst Libraries

Active polymerization catalysts , novel resin-bound diimine complexes of nickel(II ) and palladium(II ) are obtained by combinatorial synthesis and combined in a catalyst library. By tagging with fluorescent markers, the catalysts can be coded. Therefore, after cleavage of the tag from the polymer-coated resin, HPLC can be used to determine the pathway along which the products were formed.     

Carbon-supported palladium catalysts for fuel cells

Small controlled amounts of palladium were electrochemically deposited onto various carbon supports from solutions of glycinate-chloride complexes of palladium(II) in order to obtain palladium catalysts suitable for use in fuel cells. The catalytic activity of the resulting catalytic layers was studied in reactions of reduction of atmospheric oxygen and oxidation of methanol and ethanol in acid and alkaline media by measuring cyclic voltammetric curves on a rotating disk electrode.     

Efficient addition of alcohols, amines and phenol to unactivated alkenes by Au(III) or Pd(II) stabilized by CuCl2

The nucleophilic addition of alcohols, amines and phenol to unactivated alkenes catalyzed by cationic gold and palladium becomes limited due to the fast reduction into metallic gold under reaction conditions. The presence of CuCl2 retards the reduction of Au(III) and Pd", strongly increasing the turnover number of gold and palladium catalysts. It is shown that new Au(III)-CuCl2 and Pd(II)-CuCl2 catalysts are active and selective for the nucleophilic addition of alcohols, amines and phenol to unactivated alkenes.     

Formation and Properties of Hydrogenation Catalysts Based on Palladium Complexes with Primary Phosphines

The formation and catalytic properties of hydrogenation catalysts based on palladium(II) complexes with primary phosphines were studied. With the use of IR and UV spectroscopy, XRD analysis and GLC, it was found that the interaction of bis(acetylacetonato)palladium(II) or palladium(II) acetate with primary phosphines in an inert atmosphere resulted in the formation of polynuclear palladium complex associates mainly containing μ³-PR and a coordinated phosphine. Polynuclear palladium complexes and the palladium phosphide Pd₆P, which is formed from these complexes in an atmosphere of hydrogen, serve as supports for Pd(0) clusters. The effects of the ratio between initial components and the nature of the acido ligand at the palladium atom on the optimum conditions of catalyst formation were considered.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 609–614.Original Russian Text Copyright © 2005 by Belykh, Goremyka, Gusarova, Sukhov, Shmidt.     

Double Carbonylation of Organohalogen Compounds Catalyzed by Polymer-Bound Palladium Complexes

Palladium complex-catalyzed double carbonylation is a recently discovered reaction in organotransition metal chemistry. In this paper, some polymer-bound palladium complexes-polystyrylphosphine-palladium(0) complexes, poly-2-vinylpyridine-palladium(II) complexes, and poly-2-Af-vinylpyrrolidone-palladium(II) complexes have been prepared and characterized. The complexes were tested as catalysts in the double carbonylation reaction. Among these catalysts, polystyrylphos-phine-palladium(0) complexes showed good activity and selectivity, and can be easily recovered and reused. The influence of experimental parameters was investigated as well.     

Effective binuclear Pd(II) complexes for Suzuki reactions in water

A series of new ionic binuclear Pd(II) complexes supported by water‐soluble bis(α‐diimine) ligands were prepared and employed as catalysts for the palladium‐catalyzed Suzuki reaction in aqueous media. The binuclear nature of the complexes increased the reaction rate, while electronic and steric modification of the ligand frameworks had a remarkable influence upon the catalytic activity of the palladium complexes. The catalysts were shown to be homogeneous through mercury poisoning experiments and complexes could be recycled more than 10 times without loss of catalytic activity. Copyright © 2013 John Wiley & Sons, Ltd.     

Palladium-catalysed cyclisation of 2-substituted halogenoarenes by dehydrohalogenation

Cyclodehydrohalogenation mediated by various palladium catalysts and solvents with different bases (the most generally satisfactory system being palladium(II) acetate in NN-dimethylacetamide (DMA) with sodium carbonate as base) has been examined as a route to some heterocyclic systems. Whereas dehydrogenative cyclisation processes require stoichiometric amounts of palladium(II) reagent, the present procedure involves only catalytic amounts (0.1 molar proportion, or less), of palladium compound. The preparation of dibenzofuran, carbazole, fluorenone, phenanthridone, 6H-dibenzo c,e][l,2]thiazine-5,5-dioxide, 6H-dibenzo[b,d]pyran and benzofurano[2,3b]pyridine derivatives is described. The cyclisation of 3-benzamido-2-chloropyridine to 6-hydroxybenzoc][1,5]naphthyridne illustrates the regiospecificity of the process.     

Sequential actions of cobalt nanoparticles and palladium(II) catalysts: three-step one-pot synthesis of fenestranes from an enyne and an alkyne diester

A three-step one-pot synthesis of fenestranes from a readily available enyne and an alkyne diester has been carried out with cobalt nanoparticles and palladium(II) as catalysts.