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1.
Trialkylphosphine oxides extract more effectively chloride complexes of platinum than of palladium(II). Of the examined tributylphosphine (TBPO), trioctylphosphine (TOPO), and triphenylphosphine (TPPO) oxides the latter one makes possible best separation of these metals.The extraction of platinum with TPPO from solutions containing platinum and palladium unfavorably decreases with increasing palladium concentration. Using 0.1 M TPPO solution in dichloroethane, at HCl concentration 7.5 M, it is possible to separate 2–200 μg Pt/ml at a palladium concentration not higher than 10 mg/ml.Separation of platinum from macroamounts of palladium has been combined with spectrophotometric determination of platinum by means of stannous chloride. The method has been applied to the analysis of palladium for platinum content. 相似文献
2.
G. N. Altshuler L. A. Sapozhnikova O. G. Altshuler N. V. Malyshenko G. Yu. Shkurenko 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(4):663-667
Redox reactions involving hydrogen and oxygen in the presence of hybrid nanocomposites containing palladium and copper or
palladium and silver in a cis-tetraphenylcalix[4]resorcinarene polymer matrix were studied. In the composites containing palladium and copper, the redox
transformations involved copper. In the composites with palladium and silver, the redox reactions involved the polymer matrix.
The reductions in the metal-polymer nanocomposites were catalyzed by palladium. 相似文献
3.
K. C. Srivastava 《中国化学会会志》1974,21(3):163-166
A new, sensitive spectrophotometric method for the determination of palladium(II) with methylthymol blue has been developed. The palladium methylthymol blue complex has an absorption maximum at 530 nm. The colour reaction has a sensitivity of 0.005 µg of palladium/cm2 and obeys Beer's Law over the range 0.4 to 3.24 ppm of palladium. The effects of concentration of perchloric acid, reagent, heating, stability of colour and diverse ions have been investigated. The ratio of metal: ligand in the complex is 1:1 and the formation constant was calculated to be 1.18×104. 相似文献
4.
Braulio Aranda Sergio A. Moya Andres Vega Gonzalo Valdebenito Sofia Ramirez‐Lopez Pedro Aguirre 《应用有机金属化学》2019,33(4)
Aminocarbonylation of aryl halides, homogeneously catalysed by palladium, is an efficient method that can be employed for obtaining amides for pharmaceutical and synthetic applications. In this work, palladium (II) complexes containing P^N ligands were studied as catalysts in the aminocarbonylation of iodobenzene in the presence of diethylamine. Two types of systems were used: a palladium (II) complex formed in situ; and one prepared prior to the catalytic reaction. In general, the palladium complexes studied achieved high conversions in an average reaction time of less than 2 hr, which is less than that for the standard system (Pd (II)/PPh3) used. The pre‐synthesized complexes were faster than their in situ counterparts, as the latter require an induction time to form the Pd/P^N species. The structure and electronic properties of the ligand P^N can influence both the activity and the selectivity of the reaction, stabilizing the acyl‐palladium intermediates formed in a better manner. 相似文献
5.
Karl-Heinz Lubert Markus Guttmann Lothar Beyer 《Journal of Solid State Electrochemistry》2002,6(8):545-552
The study of the electrode reactions of palladium(II) at non-modified carbon paste electrodes (CPEs) in chloride solution
has revealed the existence of a chloropalladate(II) complex at the electrode surface. The complex is formed during the application
of anodic potentials after preceding palladium deposition. In the present paper the electrode reactions of PdII at CPEs modified with some N′,N′-disubstituted derivatives of N-benzoylthiourea [as selective ligands for palladium(II)] are studied in chloride solution by cyclic voltammetry. Two reduction
peaks are observed in the cathodic scans recorded after deposition of palladium and anodization of the electrode. From the
results it is concluded that [in addition to the chloropalladate(II) complex, observed at the non-modified electrode] a second
palladium complex is formed at positive potentials. The formation of the palladium(II) complex of the N-benzoylthiourea derivatives by ligand exchange at the electrode surface is assumed. The ligand exchange itself occurs without
charge transfer across the electrode|solution interface; therefore, it cannot be detected electrochemically. After palladium
deposition and anodic treatment a pronounced "inverse" peak (i.e., an anodic peak in the cathodic scan) with peak currents
up to 100 μA is observed at about +0.8 V. Its peak current increases with the amount of deposited palladium and the number
of cycles. The reactions at the electrode surface are discussed. The results of the study reveal the existence of two different
surface complexes of palladium(II) at ligand-modified CPEs, but the surface reactions could not be elucidated in detail.
Electronic Publication 相似文献
6.
T. G. Nikiforova 《Russian Journal of Electrochemistry》2010,46(12):1378-1382
Reduction of palladium(II) glycinate complexes in strongly acid 0.5 M NaClO4 solutions (pH 0.6 and 1.0) with variable palladium(II) complex and free glycine concentration was studied by the taking of
cyclic voltammograms at palladium rotating disc electrode. It is shown that it was a chelate monoglycinate palladium(II) complex
that was present in all studied solutions and underwent the reduction. The diffusion coefficient of the chelate monoglycinate
palladium(II) complex D = (6.5 ± 0.5) × 10−6 cm2/s was determined from the limiting diffusion current of the complex reduction. The monoglycinate palladium(II) complex reduction
occurred in the double-layer segment of the palladium charging curve; it was not complicated by hydrogen adsorption at electrodes.
The palladium(II) complex reduction half-wave potential was determined (E
1/2 = ∼0.300 to 0.330 V (SCE)). It is shown that the decreasing of the number of ligands coordinated by palladium via nitrogen
atom facilitates the complex reduction process. In particular, the reduction potentials of palladium(II) complexes with different
ligand number at palladium electrode shifted markedly toward negative potentials in the series: Pdgly+ < Pd(gly)2 < Pd(gly)42−. 相似文献
7.
Jin Yang 《Journal of Coordination Chemistry》2017,70(3):441-450
Four heteroleptic palladium complexes containing both N-heterocyclic carbenes and 1H-benzotriazole were synthesized and characterized. The solid-state structures show mononuclear carbene palladium complexes with each palladium coordinated by an NHC, the 3-position nitrogen of 1H-benzotriazole and two trans chlorides. The catalytic performance of the complexes for Mizoroki–Heck and Sonogashira reactions were further investigated. The results reveal that the complexes show high catalytic activities for coupling of aryl bromides with alkenes and alkynes. 相似文献
8.
《中国化学》2018,36(10):929-933
A new palladium‐catalyzed selective aminomethylation of conjugated 1,3‐dienes with aminals via double C—N bond activation is described. This simple method provides an effective and rapid approach for the synthesis of linear α,β‐unsaturated allylic amines with perfect regioselectivity. Mechanistic studies disclosed that one palladium catalyst cleaved two distinct C—N bond to furnish a cascade double C—N bond activation, in which an allylic 1,3‐diamine and allylic 1,2‐diamine were initially formed as key intermediates through the palladium‐catalyzed C—N bond activation of aminal and the α,β‐unsaturated allylic amine was subsequently produced via palladium‐catalyzed C—N bond activation of the allylic diamines. 相似文献
9.
Sang Chul Shim Dong Yub Lee Li Hong Jiang Tae Jeong Kim Sung-Dong Cho 《Journal of heterocyclic chemistry》1995,32(1):363-365
The palladium catalyzed carbonylative cyclization of o-bromobenzaldehyde 1 in alcoholic solution gave 3-alkoxyphthalides 3a-e in 61–85% isolated yields via intramolecular cyclization induced by the coordinated formyl group on the palladium. 相似文献
10.
The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analysis of 106 compounds containing palladium atoms surrounded by halogen atoms. Depending on the oxidation number (2 or 4), Pd atoms can bind 4 to 6 X atoms (X = Cl, Br, I) and form PdX
n
coordination polyhedra shaped like octahedra or square pyramids (n = 6), square pyramids (n = 5), or squares (n = 4). A lone electron pair on Pd(II) was found on the basis of X-ray diffraction data. The influence of the palladium valence state on the key stereochemical features of palladium halide complexes is considered in terms of the 18-electron rule. The tendency of palladium atoms to Pd···H aghostic interactions was noted. 相似文献
11.
M. A. Taher A. Mostafavi S. Z. Mohammadi Mobarakeh 《Journal of Analytical Chemistry》2007,62(11):1022-1027
This work assesses the potential of natural analcime zeolite as a sorbent for the preconcentration of palladium. Palladium
is quantitatively retained on modified analcime zeolite loaded with zincon using the column method in the pH range from 2.5
to 3.5 at a flow rate of 1 mL/min. The palladium complex was removed from the column with 5.0 mL of dimethylsulfoxide (DMSO)
and determined by third-derivative spectrophotometry. The detection limit is 0.03 μg/mL (signal-to-noise ratio = 3) in the
final solution. Since it is possible to retain 0.15 μg of palladium from 600 mL of solution passing through the column, elution
with 5.0 mL of DMSO gives a detection limit of 0.25 ng/mL for palladium in the initial aqueous solution. The calibration curve
is linear over the range 0.1 to 5.0 μg/mL of palladium(II) in the final solution with a correlation coefficient of 0.9996.
Seven replicated determinations of 5.0 μg of palladium in 5.0 mL dimethylsulfoxide gave a mean d
3
A/dλ3 (peak-to-peak signal between λ2 = 625 and λ1 = 654 nm) of 0.64 with a relative standard deviation of 1.2%. The sensitivity of the method (d
3
A/dλ3) is 0.5843 mL/μg of palladium(II) from the slope of the calibration curve. The interference of a large number of anions and
cations has been studied and the optimized conditions developed were utilized for the determination of trace palladium in
various synthetic and water samples.
The text was submitted by the authors in English. 相似文献
12.
Novel (N‐heterocyclic carbene)Pd(pyridine)Br2 complexes for carbonylative Sonogashira coupling reactions: Catalytic efficiency and scope for arylalkynes,alkylalkynes and dialkynes
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Mansur Ibrahim Imran Malik Waseem Mansour Muhammad Sharif Mohammed Fettouhi Bassam El Ali 《应用有机金属化学》2018,32(4)
New N,N′‐substituted imidazolium salts and their corresponding dibromidopyridine–palladium(II) complexes were successfully synthesized and characterized. Reactions of palladium bromide with the newly synthesized N,N′‐substituted imidazolium bromides ( 2a and 2b ) in pyridine afforded the corresponding new N‐heterocyclic carbene pyridine palladium(II) complexes ( 3a and 3b ) in high yields. Their single‐crystal X‐ray structures show a distorted square planar geometry with the carbene and pyridine ligands in trans position. Both complexes show a high catalytic activity in carbonylative Sonogashira coupling reactions of aryl iodides and aryl diiodides with arylalkynes, alkylalkynes and dialkynes. 相似文献
13.
L. B. Belykh N. I. Skripov L. N. Belonogova V. A. Umanets T. P. Stepanova F. K. Schmidt 《Kinetics and Catalysis》2011,52(5):702-710
The catalytic properties and nature of the nanoparticles forming in the system based on Pd(dba)2 and white phosphorus are reported. A schematic mechanism is suggested for the formation of nanosized palladium-based hydrogenation
catalysts. The mechanism includes the formation of palladium nanoclusters via the interaction of Pd(dba)2 with the solvent (N,N-dimethylformamide) and substrate and the formation of palladium phosphide nanoparticles. The inhibiting effect exerted by
elemental phosphorus on the catalytic process is due to the conversion of part of the Pd(0) into palladium phosphides, which
are inactive in hydrogenation under mild conditions, and the formation of mainly segregated palladium nanoclusters and palladium
phosphide nanoparticles. By investigating the interaction between Pd(dba)2 and white phosphorus in benzene, it has been established that the formation of palladium phosphides under mild conditions
consists of the following consecutive steps: Pd(0) → PdP2 → Pd5P2 → Pd3P. It is explained why white phosphorus can produce diametrically opposite effects of on the catalytic properties of nanosized
palladium-based hydrogenation catalysts, depending on the nature of the palladium precursor. 相似文献
14.
Hydrogen adsorption on palladium black and palladium supported on activated carbon was characterized by the Temperature Programmed Desorption technique (TPD) using the radiotracer tritium. It is shown that there are five energetic desorbed hydrogens with peak maxima at —50, 35, 115, 350, and 580°C. An additional peak at — 120°C hydrogen desorbed from activated carbon was observed on Pd/C. An isotopic hydrogen separation experiment was designed to demonstrate that hydrogen only dissociatively adsorbed on palladium surfaces whereas it was associatively adsorbed on activated carbon. 相似文献
15.
Vladimir P. Petrovi? Svetlana Markovi? Zorica D. Petrovi? 《Monatshefte für Chemie / Chemical Monthly》2011,17(1):141-144
Abstract
The mechanism of the formation of the active Pd(0) complex from trans-dichlorobis(diethanolamine-N)palladium(II) complex in the presence of strong base was investigated by using density functional theory (M06 method). Our investigation shows that in the basic environment trans-dichlorobis(diethanolamine-N)palladium(II) complex undergoes abstraction of the alcoholic proton, and coordination of alkoxide oxygen to palladium. The intermediate complex, in which hydrogen is coordinated to Pd, undergoes reductive elimination of HCl, yielding the catalytically active low ligated Pd(0) complex. 相似文献16.
Anu Naik Liu Meina Manfred Zabel Dr. Oliver Reiser Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(5):1624-1628
The palladium‐catalyzed aerobic oxidation of alkenes and especially styrenes (Wacker oxidation) by using chiral pseudo C2‐symmetrical bis(isonitrile) ligands in the absence of further cocatalysts gives rise to methyl ketones in a highly chemoselective manner. The palladium bis(isonitrile) catalyst was characterized by NMR spectroscopy and X‐ray structure analysis, revealing a dissymmetric coordination of palladium by the two isonitrile moieties. 相似文献
17.
Mohammad Akbar Ali Aminul H. Mirza Ray J. Butcher Karen A. Crouse 《Transition Metal Chemistry》2006,31(1):79-87
New complexes of general formula, [M(NNS)Cl] (M = PdII, PtII; NNS = anionic forms of the 6-methyl-2-formylpyridine Schiff bases of S-methyl- and S-benzyldithiocarbazates) have been prepared and characterized by a variety of physico-chemical techniques. Based on conductance
and spectral evidence, a square-planar structure is assigned to these complexes. The crystal and molecular structure of the
[Pd(mpasme)Cl] complex (mpasme=anionic form of the 6-methyl-2-formylpyridine Schiff base of S-methyldithiocarbazate) has been
determined by X-ray diffraction. The complex has a distorted square-planar geometry with the ligand coordinated to the palladium(II)
ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the thiolate sulfur atom; the fourth coordination position around
the palladium(II) ion is occupied by the chloride ligand. The distortion from a regular square-planar geometry is ascribed
to the restricted bite angle of the ligand. Both the Schiff bases exhibit strong cytotoxicity against the human ovarian cancer
(Caov-3) cell lines, the S-methyl derivative being two times more active than the S-benzyl derivative. The [Pt(mpasme)Cl] complex is moderately active but the palladium(II) complex is weakly active against
this cancer. None of the complexes of Hmpsbz are active against Caov-3. The Schiff base, Hmpasme exhibits moderate activity
against the bacteria, MRSA, P. aeruginosa and S. typhimurium but is inactive against B. subtilis. Coordination of the ligand with palladium(II) substantially reduces its activity. The Schiff base, Hmpasbz and its palladium(II)
and platinum(II) complexes are inactive against these bacteria. The Schiff bases and their palladium(II) and platinum (II)
complexes are inactive against the pathogenic fungi, C. albican, Aspergillus ochraceous and Saccharomyces cerevisiae. 相似文献
18.
本文报道了有机-无机杂化材料固载的钯催化的无铜Sonogashira偶联反应。在3-[N,N-双(二苯基膦)氨基)]丙基功能化的硅胶固载的钯催化下,末端炔烃和碘代芳烃、溴代芳烃的偶联反应生成高产率相应的偶联产物。反应条件包括使用乙二醇为溶剂,三乙胺为碱。而且硅胶负载的膦钯催化剂和溶剂乙二醇经简单处理,可循环使用6次不降低活性。 相似文献
19.
Dr. Christophe Kahlfuss Dr. Raymond Grüber Prof. Elise Dumont Prof. Guy Royal Floris Chevallier Dr. Saioa Cobo Prof. Eric Saint-Aman Dr. Christophe Bucher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1573-1580
A dynamic supramolecular approach is developed to promote the π-dimerization of viologen radicals at room temperature and in standard concentration ranges. The approach involves cis- or trans-protected palladium centers serving as inorganic hinges linking two functionalized viologens endowed with metal-ion coordinating properties. Based on detailed spectroscopic, electrochemical and computational data, we show that the one-electron electrochemical reduction of the viologen units in different dynamic metal/ligand mixtures leads to the formation of the same intramolecular π-dimer, regardless of the initial environment around the metallic precursor and of the relative ratio between metal and ligand initially introduced in solution. The large-scale electron-triggered reorganization of the building blocks introduced in solution thus involves drastic changes in the stoichiometry and stereochemistry of the palladium/viologen complexes proceeding in some cases through a palladium centered trans→cis isomerization of the coordinated ligands. 相似文献
20.
A series of new chiral C2‐symmetric bis(phosphinite) ligands and their palladium(II) complexes have been synthesized and for the first time used as catalysts in the palladium‐catalysed asymmetric intermolecular Heck coupling reactions of 2,3‐dihydrofuran with iodobenzene or aryl triflate. Under optimized conditions, products were obtained with high conversions and moderate to good enantioselectivities. The new C2‐symmetric bis(phosphinite) ligands and their palladium(II) complexes were characterized using multinuclear NMR and Fourier transform infrared spectroscopies and elemental analysis. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献