Catalytic Activity Of Palladium Research Articles

Synthesis, characterization and catalytic activities of palladium(II)-imidazopyridine

The ligand 2-phenylimidazo(1,2-α)pyridine (1) was synthesized by neat reaction 2-aminopyridine and 1-bromo-acetophenone; reaction of 1 with acetonitrile solution of PdCl2 leads to [Pd(1)Cl2(CH3CN)] (2). Refluxing [Pd(1)Cl2(CH3CN)] (2) in pyridine leads to [Pd(1)Cl2(py)] (3).The complexes were characterized by various spectroscopic techniques and the solid state structure of 2 was elucidated by single crystal X-ray diffraction (SCXRD) analyses. SCXRD analyses support the square planar geometry of 2. A series of DFT calculations were also performed to gain further insight into the respective structures of the complexes. From molecular hardness calculation it is observed slightly better reactivity of 2 compared to 3. Molecular Hirshfeld surface analyses support various non-covalent secondary interactions that observed in packing of solid state structure of 2. Complexes 2 and 3 were found to facilitate Suzuki coupling reactions under relatively mild conditions and slightly better yields were obtained in case of 2.

Directed aromatic C–H functionalization of N-arylcarbamates and quinazolinones catalyzed by palladium nanoparticles supported on nitrogen-doped graphene

Pd nanoparticle‑nitrogen doped reduced graphene oxide (Pd/N-RGO) nanohybrid was successfully utilized for the C-H-acyloxylation of N-arylcarbamates and the CH halogenation of quinazolinones with N-halosuccinimides. The use of the catalyst was shown to be a highly efficient, less time-consuming and recyclable procedure for two different types of CH functionalization; it was even better than Pd(OAc)2 as its homogeneous counterpart. Additionally, the effect of introducing nitrogen into the graphene lattice on the catalytic activities of palladium was evaluated by synthesizing Pd nanoparticles-reduced graphene oxide. The catalyst exhibited no significant palladium leaching; so, it was successfully recovered and reused in ten consecutive runs without any noticeable decrease in its catalytic activity.

Synthesis, Structural Characterization and Catalytic Activities of Palladium(II) Schiff base Complexes Containing Tetradentate N2O2 & N2S2 Donor Ligands

New family of palladium(II) tetradentate complexes of the general formula [Pd(L1-4)] (L1-L3; tetradentate N2O2 donors & L4; tetradentate N2S2 donors) have been synthesized by the reaction of Pd(OAc)2 with tetradentate Schiff base ligands. The palladium(II) complexes were fully characterized by analytical, spectral (FT-IR, UV-Vis, 1H-NMR & 13C-NMR) methods. Further, the new palladium(II) complexes were tested as catalyst for Suzuki-Miyaura and Sonogashira coupling reactions and exhibits very good catalytic activity.

Heteroleptic Palladium(II) Complexes of Thiazolinyl‐picolinamide Derived N∩N∩N Pincer Ligand: An Efficient Catalyst for Acylative Suzuki Coupling Reactions

AbstractSynthesis, reactivity, characterization, and catalytic activities of a series of palladium(II) complexes containing the thiazolinyl‐picolinamide derived pincer ligand is reported. Treatment of 2‐aminobenzonitrile with cysteamine and subsequent treatment with 2‐picolinic acid afforded the thiazolinyl‐picolinamide derived tridentate pincer ligand N∩N∩N (2). Treatment of 2 either with (COD)PdCl2 or PdCl2 in 1 : 1 ratio afforded the palladium(II) complex [(κ3‐N∩N∩N)PdCl] (3). A reaction between Pd(OAc)2 and 2 in equimolar ratio in dichloromethane gave [(κ3‐N∩N∩N)Pd(η1‐OAc)] (4) which on further treatment with triflic acid in acetonitrile produced the [(κ3‐N∩N∩N)Pd(N≡C−CH3)]OTf (5). The complex 5 was further treated with auxiliary ligands to produce the cationic heteroleptic palladium complexes, [(κ3‐N∩N∩N)Pd(NC5H5)]OTf (6), [(κ3‐N∩N∩N)Pd(NC5H4CN)]OTf (7), and [(κ3‐N∩N∩N)Pd(NC5H4NMe2)]OTf (8), respectively. The newly synthesized compounds were characterized by 1H and 13C{1H} NMR spectroscopic techniques and the molecular structures of 2–4, 6 and 8 were established. The catalytic activity of palladium(II) complexes (3–8) were evaluated for the acylative Suzuki coupling reaction between aryl carboxylic acids and arylboronic acids to yield unsymmetrically substituted biaryl ketones. The effect of reaction conditions viz., solvent, base, temperature, catalyst loading were evaluated, and complex 4 was found to be an excellent catalyst with a maximum TOF of 19.8 min−1.

Direct C‐H Bond Arylation of C2‐Blocked Pyrrole with Aryl Halides Using Palladium(II)‐N‐Heterocyclic Carbene Catalysts

AbstractHerein we report synthesis of seven new palladium(II)‐NHC complexes with the general formula [PdX2(NHC)2], (NHC=1,3‐dialkylbenzimidazol‐2‐ylidene, X=Cl or Br). The structures of all the new compounds were characterized by 1H NMR, 13C NMR, FT‐IR spectroscopy and elemental analysis techniques. The catalytic activities of palladium(II)‐NHC complexes were tested in the direct C−H bond arylation of C2‐blocked pyrrole with various aryl halides in presence of 1 mol% catalyst loading at 120 °C for 1–16 h. Under the given conditions, palladium(II)‐NHC complexes showed the good catalytic performance for the direct C−H bond arylation of C2‐blocked pyrrole with aryl bromides, and with readily available and inexpensive aryl chlorides. In all cases, the C−H bond arylation regioselectively produced C5‐arylated products in moderate to high yields.

Palladium(II)-N-heterocyclic carbene-catalyzed direct C2- or C5-arylation of thiazoles with aryl bromides

Herein we report, a series of new benzimidazolium chlorides as N-heterocyclic carbene (NHC) ligand and their corresponding palladium(II)-NHC complexes with the general formula [PdCl2(NHC)2] were synthesized. All new compounds were characterized by 1H NMR, 13C NMR, IR spectroscopy and elemental analysis techniques. The catalytic activity of palladium(II)-NHC complexes was investigated in the direct C2- or C5-arylation of thiazoles with aryl bromides in presence of palladium(II)-NHC at 150 °C for 1 h. These complexes exhibited the good catalytic performance for the direct arylation of thiazoles. The arylation of thiazoles regioselectively produced C2- or C5-arylated thiazoles in moderate to high yields.

The catalytic activity of Palladium(II) complexes containing PN ligands in the Heck and Suzuki C-C coupling reactions

A range of iminophosphine (PN) ligands ((C 6 H 5 ) 2 P-C 6 H 4 -CH=NR (R=-C 6 H 3 (2-CH 3 )(4-OH) ( 1a ), -CH 2 CH 2 C 6 H 4 (4-OH) ( 1b ) and -C 5 H 3 N(2-CH 3 ) ( 1c )) have been synthesized starting from 4-amino-3-methylphenol, 4-(2-aminoethyl)phenol and 2-amino-3-methylpyridine with 2-(diphenylphosphino)benzaldehyde. The PN ligands were reacted with Pd(cod)Cl 2 to give corresponding new PdLCl 2 metal complexes, ( 2a , 2b and 2c ). The Heck and Suzuki C-C coupling reactions were examined with catalysts 2a - 2c and showed high conversions under the determined conditions with para substituted arylhalides

Effect of Microwave Irradiation on the Catalytic Activity of Palladium Supported Catalysts in the One-Step Isomerisation of Cinchona Alkaloids to \u03943,10-Isobases

Efficiency of palladium solid supported (Pd/SS) catalysts for one-step isomerisation of the side chain of four natural Cinchona alkaloids have been explored under controlled microwave heating in the green media (50% aqueous ethanol or ethylene glycol with HCl). Conversion progress and products purity was monitored by TLC and by 1H NMR spectrometry. Final conversion is dependent on the support (Al2O3, C or BaSO4), reaction time and temperature. Very good results: high yields and purity of (Z/E) Δ3,10-isomers were obtained from quinine and quinidine with 10% Pd/BaSO4 as the catalyst, which is less effective for isomerisation of cinchonine and cinchonidine. Enhancing energy efficiency can be possible when the responsive support selective absorbs of microwave energy, which is translated to the palladium giving acceleration of the formation and disintegration of the transition state leading to Δ3,10-isomers.Graphical

A simple and highly selective fluorescent sensor for palladium based on benzofuran-2-boronic acid

Abstract Benzofuran-2-boronic acid could be used as a fluorescent sensor for the detection of Pd2+ because it was rapidly converted to highly fluorescent derivative after mixing with Pd2+ under basic condition at room temperature. We found that dimerization of benzofuran was occurred to form fluorescent derivative by the catalytic activity of palladium. The fluorescence intensity at 360 nm increased with increasing the concentration of Pd2+. The excellent selectivity for Pd2+ was demonstrated among other metal ions. Based on this findings, we successfully applied benzofuran-2-boronic acid to develop a microplate-based assay for high-throughput measurement of Pd2+. The detection limit (blank + 3SD) for Pd2+ of the proposed assay was 9.8 nM.

Novel phosphorus-coordinated palladium(II) complexes derived from 3,5-disubstituted-1H-1,2,4-diazaphospholes: Synthesis and catalytic application in Suzuki-Miyaura cross-coupling reactions

Four novel phosphorus-coordinated palladium(II) complexes(I-IV) were easily prepared by the reaction of 3,5-disubstituted-1H-1,2,4-diazaphospholes with Pd(CH3CN)2Cl2 at room temperature and characterized. The catalytic activity of palladium(II) complexes was further evaluated in Suzuki-Miyaura reaction of aryl halides with arylboronic acids, giving the biphenyl derivatives in good yields.

Optimization of metal atomic ratio of PdxRuyNiz on carbon support for ethanol oxidation

The catalytic activity of palladium (Pd) on an alloy catalyst on carbon supports with regards to ethanol oxidation was enhanced by systematically varying the atomic ratio of Pd, ruthenium (Ru), and nickel (Ni) alloy catalyst. Each atomic ratio catalyst was investigated so as to find the highest current density per mass of palladium. Functionalized carbon black (C) and reduced graphene oxide (rGO) were used as carbon supports. The PdxRuyNiz/carbon catalysts were prepared by impregnation and reduction method with sodium borohydride (NaBH4) being used as the reducing agent. Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) were used to characterize the functionalized carbon supports, and the synthesized PdxRuyNiz/carbon catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and inductively coupled plasma (ICP). The electrical properties of catalyst were performed by cyclic voltammetry (CV), chronoamperometry (CA), and CO-stripping to investigate the catalytic activity compared to 20%wt synthesized Pd/C. The results showed that Pd:Ru:Ni=60:0:40 on rGO (Pd60Ni40/rGO) had the best metal atomic ratio and support for the electro-oxidation of ethanol. The maximum current density and the electrochemical surface area were 11,074mAcm−2mg−1Pd and 55.6m2g−1Pd, which were 1.7 and 2.67 times the corresponding values of synthesized Pd/C, respectively.

Synthesis, Characterization and Catalytic Activities of Palladium(II) Nitroaryl Complexes

Two palladium(II) nitroaryl complexes trans-[bromo(p-nitrophenyl)bis(triphenylphosphine)palladium(II)] 1 and trans-[bromo(2,4-dinitrophenyl)bis(triphenylphosphine)palladium(II)] 2 have been synthesized. The complexes were characterized by FTIR and NMR (1H, 13C and 31P) spectroscopy and elemental analysis. The molecular structure of complex 2, as confirmed by X-ray crystallography, reveals that the Pd atom and its neighboring groups (two PPh3, Br and phenylene group) lie in a slightly distorted square plane. In the UV–Vis spectra of the complexes 1 and 2, the palladium to aryl charge transfer bands were observed. The emission peaks from the singlet excited states (S1 → S0) were observed in the photoluminescence spectra of the complexes. The thermal stability of the complexes has been studied by thermal gravimetric analysis (TGA). TGA data showed that both complexes are thermally stable up to 200 °C, and complex 1 is more stable than 2. The catalytic efficiency of the new palladium(II) complexes was studied as demonstrated using the Sonogashira coupling reactions with good yields. The experimental results suggest that the Sonogashira coupling reactions can be performed at moderate temperature (50 °C) using these new palladium(II) complexes as catalysts.

Catalytic activity of palladium nanocubes/multiwalled carbon nanotubes structures for methyl orange dye removal

In this work, the synthesis and catalytic activity measurements of a nanostructured material formed by palladium (Pd) nanocubes supported on multiwalled carbon nanotubes (MWCNTs) for removing methyl orange as a model of organic contaminant from aqueous solution are presented. The nanocubes were synthesized by a reduction process of H2PdCl4 and a non-covalent method that involves a surfactant functionalization of the carbon nanotubes was used to produce the nanostructured material. Characterization was performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis. Results showed well dispersed Pd nanocubes, in the range of 15–25nm, bonded onto the carbon nanotubes. The catalytic experiments exhibited 81.9% methyl orange removal after 8min and 99% after 60min using 1mg of the nanostructured material per every 20mg/L of the dye.

Large-scale synthesis of palladium concave nanocubes with high-index facets for sustainable enhanced catalytic performance.

The catalytic activity of palladium (Pd) nanostructures highly relies on their size and morphology, especially enclosed with high-index facets, which provide more active sites so as to enhance their catalytic performance comparing with their low-index facet counterparts. Herein, Pd concave nanocubes enclosed with {730} facets by a one-pot scalable liquid method, with various high-index facets are synthesized via tuning reduction kinetics. Due to their high-index facets, the Pd concave nanocubes exhibit much higher electrocatalytic activity and stability for methanol oxidation than the Pd nanocubes enclosed by {100} facets and commercial Pd/C. Furthermore, we scale up synthesis of Pd concave nanocubes by expanding the volume of all species to fifty times with high-yield production.

Catalytic activity of palladium and gold dendrimer-encapsulated nanoparticles for methylene blue reduction: A kinetic analysis

A kinetic analysis of the catalytic reduction of methylene blue (MB) by sodium borohydride (BH4−) using colloidal dendrimer-encapsulated palladium (Pd) and gold (Au) nanoparticles (PdDENs and AuDENs) is presented. The nanoparticles were prepared by the template method using generation 4 (G4) and generation 5 (G5) hydroxyl-terminated poly (amido)amine (PAMAM-OH) dendrimers for PdDENs and amine-terminated poly (amido)amine (PAMAM-NH2) for AuDENs in aqueous solution. The catalysts were characterized by UV/vis spectrophotometry and transmission electron microscopy (TEM). The sizes of the particles obtained ranged from 1.3 to 2.3nm with volume normalized surface areas between 0.02 and 0.06m2L−1. The reduction of MB by BH4− was monitored by UV/vis spectrophotometry using the stopped-flow technique and the kinetic data obtained was modeled to the Langmuir–Hinshelwood mechanism. The apparent rate constant for the reduction is related to the surface area S of the nanoparticles, the adsorption constants of MB (KMB) and BH4−(KBH4−) as well as to the kinetic constant k which is related to the rate-determining step of the reaction. The kinetic constant k was largest for PdDENs with the largest volume normalized surface area of 0.06m2L−1. KMB values were 10 times larger than those of KBH4− in the case of PdDENs. The activation energy was lowest for the most catalytic active PdDENs at 34.5±1.5kJmol−1 as compared to 71.3±1.6kJmol−1, for the least active AuDEN catalyst.

The Effect of Electron-withdrawing Group Functionalization on Antibacterial and Catalytic Activity of Palladium(II) Complexes

] (2), [HL1 = 2-((E)-(2,6-diethylphenylimino)methyl)-4,6-dibromophenol, L2 = (E)-N-benzylidene-2,6-diethylbenzenamine], which are obtained by functionalizingSchiff base ligands with or without electron-withdrawing groups. Both compounds are mononuclear structures.Comparisons are made to the compounds 1 and 2 to analyze and understand the effect of electron-withdrawinggroups. Antibacterial activity studies indicate the electron-withdrawing groups on Schiff base ligands enhanceantibacterial activity. Catalytic activity, however, is reduced due to the enhanced steric-hindrance of theelectron-withdrawing groups. Electronic absorption and emission properties of HL1, L2, 1 and 2 are alsoreported.Key Words : Palladium complexes, Electron-withdrwaing groups, Luminescence, Antibacterial activity, Cat-alytic activityIntroductionSchiff bases are important compounds due to their widerange of biological activities,

Hydrodechlorination of Carbon Tetrachloride and 1,2-Dichloroethane on Palladium Nanoparticles Supported on Metal Fluorides

Catalytic activity of palladium supported on strongly acidic aluminum fluoride or on much less acidic magnesium fluoride has been the subject of current research. Both catalysts were synthesized by non-aqueous sol-gel method with subsequent two-stage activation: post-fluorination and reduction. The catalytic behavior of prepared Pd/HS-AlF3 and Pd/HS-MgF2 in the hydrodechlorination reactions of chlorinated hydrocarbons was investigated. It was found that differences in support acidity and catalyst’s activation protocol strongly effect the catalytic performance.

ChemInform Abstract: Catalytic Activity of Palladium(II) Diaminocarbene Complexes in the Sonogashira and Suzuki Reactions.

AbstractCross‐coupling reactions of haloarenes with oct‐1‐yne (Sonogashira reaction) and phenylboronic acid (Suzuki reaction) are presented using palladium(II) complexes with chelating and non‐chelating diaminocarbene ligands as catalysts.

Catalytic Activity of Palladium(II) and Osmium(VIII) on the Oxidation of Chloramphenicol by Copper(III) Periodate Complex in Aqueous Alkaline Medium—A Comparative Kinetic and Mechanistic Approach

Chloramphenicol is considered a prototypical broad band spectrum antibiotic, alongside the tetracyclines, and finds extensive applications in pharmaceuticals. Hence, its oxidation kinetic study is of much significance in understanding the mechanistic profile in biological systems. In this regard, a systematic study of oxidation of chloramphenicol (CHP) by diperiodatocuprate(III) (DPC) in the presence of micro amounts (10–8 mol/dm3) of Pd(II) and Os(VIII) catalysts has been investigated spectrophotometrically in aqueous alkaline medium at a constant ionic strength of 0.10 mol dm–3. The reaction between CHP and DPC in alkaline medium exhibits 1:2 stoichiometry in both catalyzed reactions (CHP:DPC). The oxidation products in both reactions were found to be the same and were identified and confirmed by IR, GC-MS, and 1H NMR. The order with respect to DPC concentration was unity, while the order with respect to CHP concentration varied from first order to zero order as the concentration of CHP increased. The rates increased with increase in [OH–] and decreased with increase in [IO4–]. The order with respect to [Pd(II)] and [Os(VIII)] was unity. It is observed that the catalytic efficiency for the title reaction is in the order of Pd(II) > Os(VIII). The catalytic constant was also determined at different temperatures for both reactions. The proposed mechanisms and the derived rate laws are in concurrence with the observed kinetics. The activation parameters with respect to the limiting step of the mechanism were calculated, and the thermodynamic quantities were also determined. Kinetic experiments suggest that [Cu(H2IO6)(H2O)2], [Pd(OH)2Cl2]2–, and [OsO4(OH)2]2– are the reactive oxidizing species of Cu(III), Pd(II), and Os(VIII).

Catalytic activity of palladium(II) diaminocarbene complexes in the Sonogashira and Suzuki reactions

Palladium(II) complexes with chelating and non-chelating diaminocarbene ligands were assessed as catalysts in the cross-coupling reactions of haloarenes with oct-1-yne (Sonogashira reaction) and phenylboronic acid (Suzuki reaction). Both complexes exhibited a higher catalytic activity than traditional phosphine ligandbased systems in the Sonogashira reaction, and they ensured cross-coupling not only with iodoarenes but also with bromoarenes activated by electron-withdrawing substituents. The catalytic activities of the examined complexes in the Suzuki reaction were appreciably different: the palladium(II) complex with the chelating ligand turned out to be considerably less active than the complex with the non-chelating ligand.