Mixed Palladium Research Articles

How to Minimize Light-Organic Matter Interactions for All-Optical Sub-Cutaneous Temperature Sensing.

Penetration and emanation of light into tissue are limited by the strong interaction of light with the tissue components, especially oxygenated hemoglobin and white adipose tissue. This limits the possibilities for all-optical minimal invasive sensing. In order to minimize the optical losses of light in and out of the tissue, only a narrow optical window between 630 and 900 nm is available. In this work, we realized for the first time all-optical temperature sensing within the narrow optical window for tissue by using the process of triplet–triplet annihilation photon energy upconversion (TTA-UC) as a sensing tool. For this, we apply the asymmetrical benzo-fused BODIPY dye as an optimal emitter and mixed palladium benzo-naphtho-porphyrins as an optimal sensitizer. The TTA-UC sensing system is excited with λ = 658 nm with an extremely low intensity of 1 mW × cm–2 and is factual-protected for a time period longer than 100 s against oxygen-stimulated damage, allowing a stable demonstration of this T-sensing system also in an oxygen-rich environment without losing sensitivity. The sensing dyes we embed in the natural wax/natural matrix, which is intrinsically biocompatible, are approved by the FDA as food additives. The demonstrated temperature sensitivity is higher than ΔT = 200 mK placed around the physiologically relevant temperature of T = 36 °C.

A detailed spectrophotometric investigation of the stability constants of [PdCln(OH)4-n]2− and [PdBrn(OH)4-n]2− (n = 0–4)

Complex formation of mixed palladium (II) chloro-hydroxo and palladium(II) bromo-hydroxo complexes have been investigated employing spectrophotometry at 25 °C and an ionic strength of 1.0 M. Hyperquad Simulation and Speciation (HySS) was employed to determine the ideal titration conditions and an autotitrator (equipped with a flow-through cell) was used to accurately vary the pH over 80 and 90 intervals respectively. The stability constants (log βn) for the mixed chloro-hydroxo complexes [PdCl4-n(OH)n]2− (n = 0–4), are: log β1 = 18.36, log β2 = 23.21, log β3 = 26.91 and log β4 = 29.68. These newly obtained values represent a more accurate representation for the stability constants of the mixed palladium(II) chloro-hydroxo speciation. The same experimental procedure was employed to calculate, for the first time, the stepwise stability constants of the palladium(II) bromo-hydroxo system, [PdBr4-n(OH)n]2− (n = 0–4), i.e. log β1 = 18.73, log β2 = 22.25, log β3 = 25.58 and log β4 = 28.47. Molar absorption spectra for all the complexes in question have been obtained. For both systems, complete Pourbaix diagrams were constructed from the new speciation data showing the predominant species for each system.

Rapid and selective recovery of palladium from platinum group metals and base metals using a thioamide-modified calix[4]arene extractant in environmentally friendly hydrocarbon fluids

A novel macrocyclic calix[4]arene extractant having a long alkyl chain thioamide, 25,26,27,28-tetrakis(N-n-octylthiocarbamoyl)methoxy-5,11,17,23-tetra-tert-butylcalix[4]arene (1), was synthesized from 25,26,27,28-tetrakis(N-n-octylcarbamoyl)methoxy-5,11,17,23-tetra-tert-butylcalix[4]arene (2) using Lawesson’s reagent. Extractant 1 was characterized using 1H NMR, 13C NMR, FT-IR spectroscopy, and elemental analysis. The Pd(II) extraction abilities of 1 and 2 were studied in high-boiling-point and environmentally friendly hydrocarbon diluents. Pd(II) extraction experiments were conducted using single-metal Pd(II) solutions, simulated mixed palladium group metal (PGM) solutions, and acid-leached automotive catalyst residue solutions. Different experimental conditions, including the shaking time, HCl/HNO3 concentration, Pd(II) concentration, extractant concentration, and the organic/aqueous phase ratio, were studied systematically. Extractant 1 showed very selective (> 99.9%) Pd(II) extraction from the mixed PGM/base metal solutions and the acid-leached automotive catalyst residue solution. Conversely, the Pd(II) extraction ability of extractant 2 was found to be negligible. Extractant 1 showed very fast extraction kinetics and a high extraction capacity as compared to those of the commercial extractant di-n-octyl sulfide. Effective stripping of Pd(II) from 1 was performed using HCI, HNO3, NH3, and HCl-thiourea solutions. Furthermore, 1 was successfully recycled over five extraction/stripping cycles. The Pd(II) extraction mechanism of 1 was studied using FT-IR spectroscopy. Extractant 1 exhibited very selective Pd(II) extraction and high acid stability, demonstrating its industrial applicability for the extraction of Pd(II) from leached automotive catalyst liquors containing PGMs and base metals.

Palladium/Beta zeolite passive NOx adsorbers (PNA): Clarification of PNA chemistry and the effects of CO and zeolite crystallite size on PNA performance

Model 0.3 wt% and 1 wt% Pd/Beta was synthesized with nano-sized Beta crystals (average size <50 nm) and defect-free large micrometer sized crystals with similar Si/Al ratios ∼13 and 15. With the aid of FTIR we reveal the formation of at least two Pd(II)–NO and one Pd(I)–NO complexes upon NO adsorption on those materials under conditions relevant to PNA. Under higher NO pressures at room temperature, we detect the formation of the first palladium(II) dinitrosyl Pd(NO)2 complex, not observed previously on the solid supports or in organometallic compounds.O2 in dry streams promotes NO storage via additional formation of nitrosyl (NO+) ions; it also leads to stabilization of significant amounts of N2O3 in BEA pores. In the presence of water, NO storage capacity is dramatically lowered. However, in the presence of CO (which is always present in exhaust gas) the performance improves. With the aid of spectroscopy and PNA measurements we show that in the presence of CO, stable mixed palladium(II) carbonyl nitrosyl complex [Pd(II)(CO)(NO)] is formed and responsible for enhanced NOx storage. This points to a general conclusion that the species responsible for NOx storage on various zeolites in the presence of water and CO, are in fact, Pd(II)(CO)(NO).Decreasing the Pd loading to 0.3 wt% improves Pd dispersion and NO/Pd storage ratio. We also demonstrate that varying crystal sizes of BEA leads to significant changes in the NOx release temperature as well as NO/Pd ratio. Larger, defect free, more hydrophobic BEA crystals store more NOx and release it at higher temperature. Furthermore, larger, defect free and more hydrophobic BEA crystals stay significantly more active for PNA after hydrothermal aging, losing little activity compared with defective nanocrystals. High-field 27Al NMR results show that larger, hydrophobic BEA crystals are more resistant to de-alumination upon hydrothermal aging (HTA), and thus are more attractive for PNA storage with Pd.

1,2,3-Triazolylidene palladium complex with triazole ligand: Synthesis, characterization and application in Suzuki–Miyaura coupling reaction in water

Palladium complex containing 1,2,3-triazolylidene and a labile triazole moiety has been prepared and characterized. Simple azide alkyne click reaction using three fold excess of dibromoethane afforded 1-(2-bromoethyl)-4-phenyl-1H-1,2,3-triazole. The latter on dehydrobromination yields N-vinyl triazole (Ntzl) which is subsequently used for preparing its triazolium salt. Further, Ntzl–Pd–Ntzl complex was prepared from triazole by simple palladation which underwent a ligand substitution reaction when treated with in situ generated triazolylidene to form Ctzl–Pd–Ntzl type complex. This mixed palladium complex was found to be highly effective in catalyzing Suzuki–Miyaura coupling reaction between aryl halides and aryl boronic acids in water at room temperature with very low catalyst loading.

Impregnated copper or palladium–copper on magnetite as catalysts for the domino and stepwise Sonogashira-cyclization processes: a straightforward synthesis of benzo[ b]furans and indoles

An impregnated copper on magnetite catalyst is a versatile system for different domino Sonogashira-cyclization processes between 2-iodophenol and different alkynes to give the corresponding substituted benzo[ b]furans. The catalyst could be recovered ten times without losing its activity. The related process using 2-iodoaniline was, however, better catalyzed by mixed palladium–copper on magnetite giving exclusively, in this case, the products arising from the Sonogashira coupling. The cyclization to the corresponding substituted indoles could be easily and quantitatively performed by zinc bromide treatment. This catalyst avoids the use of any type of expensive and difficult to handle organic ligand, showing excellent yields, under mild reaction conditions. The catalyst is very easy to remove from the reaction medium, just by using a simple magnet.

New mixed palladium—lead and palladium—tin tellurides of the NiAs type

New ternary mixed nickel arsenide-type palladium and platinum—Group 14 metal tellurides were searched for by the high-temperature ampoule synthesis combined with the X-ray powder diffraction analysis. As a result, new phases of the ternary Pd—Pb—Te and Pd—Sn—Te systems belonging to the NiAs structure type were synthesized. The crystal structure of the compound PdPb0.304(5)Te0.695(5) was determined by the Rietveld method (P63/mmc, a = 4.151(1) A, c = 5.680(1) A, Z = 2, R1 = 0.032, Rp = 0.075, wRall = 0.025). It was shown that no ordering exists in the occupancy of the main-group atom site by lead and tellurium. In the Pd—Sn—Te system, a phase isostructural with the above-mentioned compound was found. In the latter phase, there is also no ordering in the occupancy of the main-group atom site. According to the electron diffraction data, a superstructure derived from the NiAs type exists in a narrow range of the compositions PdSn0.3Te0.7—PdSn0.4Te0.6.

Palladium(II) extraction by sulfur-containing calix[4,6]arenes from hydrochloric acid solutions

The comparison of the extraction properties of calixarenes, thiacalixarenes, and calix[4,6]arene thioethers showed that methyl(thiamethyl)calix[4,6]arenes 3a and 4a have the highest extraction abilities. These extractants rapidly and completely extract palladium from hydrochloric acid solutions; regarding distribution factors achieved in the kinetic mode, they three to four orders of magnitude exceed their monodentate analogue, octylbenzyl sulfide (OBnS). Approaches are considered to enhance palladium extraction via generating mixed palladium species in low-acidity solutions and via intramolecular catalysis by the protonated oxygen atoms of alkoxy groups in the lower rim. For 1 M HCl, the kinetic order of diluent effects on palladium extraction was established. The substitution of sulfur atoms for bridging CH2 groups was discovered to enhance palladium extraction by calix[4]arene thioether 3c.

Interference-free determination of thallium in aqua regia leaches from rocks, soils and sediments by D 2-ETAAS method using mixed palladium–citric acid–lithium chemical modifier

The mixture of palladium (chloride) with citric acid and lithium is proposed as a new chemical modifier for the elimination of interference occurred during the determination of Tl in aqua regia extracts from rocks, soils and sediments by electrothermal atomic absorption spectrometry using instrumentation with deuterium-lamp background correction (D 2-ETAAS). Palladium was preferred to rhodium and platinum as to analyte stabilization, citric acid served as an effective reducing agent facilitating formation of Pd–Tl stable covalent bonds playing an important role in the analyte stabilization. Citric acid in addition helps to remove most of interfering chloride at low temperature. The further addition of Li increased significantly the robustness of chemical modifier against strongly interfering ZnCl 2 matrix by binding free chlorine into a more stable LiCl molecule. In the presence of the proposed chemical modifier the temperature for the final step of pyrolysis was adjustable up to 1000 °C, without any noticeable loss of volatile Tl species and the interference of the rest chloride matrix was significantly reduced. The application of the modifier to direct determination of Tl in aqua regia extracts from rocks, soils and sediments has ensured the characteristic mass and LOD value for the original sample 13 pg and 0.043 μg g −1, respectively (10-μL aliquots of sample) and has enabled the use of matrix-free standard solutions for attaining accurate analysis. The accuracy was verified by the analysis of certified reference samples and by the comparison of results with those found by an inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometer (ICP-oa-TOFMS) method.

Selectivity of mechanochemical chain scission in mixed palladium(ii) and platinum(ii) coordination polymers

The selectivity of ultrasound induced chain scission was studied in reversible polymers with coordinative bonds (Pd-P and Pt-P) of different strengths in series.

Catalysis of CC-coupling reactions by cyclopropenylidene palladium complexes

Several mixed palladium(II) complexes bearing 2,3-diarylcyclopropenylidene ligands (aryl = phenyl, mesityl, naphthyl) and triaryl- and trialkylphosphines have been prepared. Single crystal structure details of one of the dimeric chloro-bridged complexes as well as of two monomeric phosphine substituted complexes are presented and compared with appropriate structural features of similar 2,3-diaminocyclopropenylidene- and cycloheptatrienylidene complexes. The new complexes were tested as catalysts in Suzuki–Mijaura coupling reactions with bromo- and chloroarenes and their catalytic activity compared with that of analogous NHC- and cycloheptatrienylidene complexes.

Feasibility of employing permanent chemical modifiers for the determination of cadmium in coal using slurry sampling electrothermal atomic absorption spectrometry

Iridium and ruthenium, alone and in combination with tungsten, thermally deposited on the platform of a transversely heated graphite tube, were investigated for their suitability as permanent chemical modifiers for the determination of cadmium in coal slurries by electrothermal atomic absorption spectrometry (ET AAS). The conventional mixed palladium and magnesium nitrates (Pd–Mg) modifiers, added in solution, were also investigated for comparison. The latter one showed the best performance for aqueous solutions, and the mixed W–Ir and W–Ru permanent modifiers had the lowest stabilizing power. All of the investigated modifiers lost some of their stabilizing power when coal slurries were investigated. The Pd–Mg modifier, pure Ir and Ru, and a mixture of 300 μg W + 200 μg Ir could stabilize Cd at least to a pyrolysis temperature of 600 °C, whereas all the other combinations already failed at temperatures above 500–550 °C. Additional investigations of the supernatant liquid of the slurries supported the assumption that the high acid concentration of the slurries and/or a concomitant leaching out of the coal might be responsible for the reduced stabilizing power of the modifiers. The maximum applicable pyrolysis temperature of 600 °C was not sufficient to reduce the background absorption to a manageable level in the majority of the coal samples. High-resolution continuum source ET AAS revealed that the continuous background absorption was exceeding values of A = 2, and was overlapping with the analyte signal. Although the latter technique could correct for this background absorption, some analyte was apparently lost with the rapidly vaporizing matrix so that the method could not be considered to be rugged. A characteristic mass of 1.0 pg and a detection limit of 0.6 ng g − 1 could be obtained under these conditions.

Asymmetric Styrene Dimerization Using Mixed Palladium—Indium Catalysts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Determination of manganese in brain samples by slurry sampling graphite furnace atomic absorption spectrometry

A simple procedure for the determination of manganese in different sections of human brain samples by graphite furnace atomic absorption spectrometry has been developed. Brain sections included cerebellum, hypothalamus, frontal cortex, vermix and encephalic trunk. Two sample preparation procedures were evaluated, namely, slurry sampling and microwave-assisted acid digestion. Brain slurries (2% w/v) could be prepared in distilled, de-ionized water, with good stability for up to 30 min. Brain samples were also digested in a domestic microwave oven using 5 ml of concentrated HNO 3. A mixed palladium+magnesium nitrate chemical modifier was used for thermal stabilization of the analyte in the electrothermal atomizer up to pyrolysis temperatures of 1300 °C, irrespective of the matrix. Quantitation of manganese was conducted in both cases by means of aqueous standards calibration. The detection limits were 0.3 and 0.4 ng ml −1 for the slurry and the digested samples, respectively. The accuracy of the procedure was checked by comparing the results obtained in the analysis of slurries and digested brain samples, and by analysis of the NIST Bovine Liver standard reference material (SRM 1577a). The ease of slurry preparation, together with the conventional set of analytical and instrumental conditions selected for the determination of manganese make such methodology suitable for routine clinical applications.

Mixed ligand palladium(II) complexes of oxalate and malonate with vitamin-B6 molecules: synthesis, crystal structure and kinetics

The synthesis of six mononuclear palladium complexes of general formula [Pd(ox)/(mal)L2] and [Pd(ox)/(mal)L′] (ox = oxalate, mal = malonate, both L and L′ are vitamin-B6 molecules (I), L = pyridoxine, pyridoxal and L′ = pyridoxamine) has been achieved. The structures of these compounds were established by elemental analysis, i.r. and 13C-n.m.r. [Pd(oxalate)(pyridoxine)2] was analyzed by single crystal X-ray diffraction. It exhibits square planar coordination with bond lengths 2.015 (2) A for Pd—N and 2.010 (2) A for Pd—O. The interaction of [Pd(ox)2]2− and [Pd(mal)2]2− with L has been followed kinetically in order to look into the nature of products and the mechanism of formation under the conditions [PdII-chelate] ≫ [L] and [L′].

Synthesis, structure and catalytic application of palladium(II) complexes bearing N-heterocyclic carbenes and phosphines

A variety of mixed palladium(II) complexes bearing N -heterocyclic carbenes (NHCs) and triaryl- and trialkylphosphines [NHC(R 2 )]Pd(PR′ 3 )I 2 (R=Me, t -Bu, ( R )-1-phenylethyl; R′=Ph, o -tolyl, cyclohexyl, t -Bu) have been prepared. Crystal structure details of trans -diiodo(1,3-di- tert -butylimidazolin-2-ylidene)(triphenylphosphino)palladium(II) are presented. The complexes were tested as catalysts in the Mizoroki–Heck, Suzuki–Miyaura and Stille reactions as well as in the dimerization of phenylacetylene. In catalytic studies of the Suzuki–Miyaura cross-coupling reaction, the performance of these novel complexes was compared to the results obtained by the corresponding bis(NHC) and bis(phosphine) complexes.

Synthesis and structures of hydride-bridged palladium A-frame complexes

A series of hydride-bridged palladium A-frame complexes [Pd2R2(μ-H)(μ-dppm)2]PF6 has been prepared by reaction of [Pd2Cl2(μ-dppm)2] with 2 equiv. of a Grignard reagent, followed by addition of CBr4, NaBH4 and TlPF6. The mixed palladium–platinum species [PdPtR2(μ-H)(μ-dppm)2]PF6 were generated analogously from [PdPtCl2(μ-dppm)2], whereas the unsymmetrical dipalladium derivatives [Pd2(Mes)R(μ-H)(μ-dppm)2]PF6 were produced from the reaction of [Pd(Mes)(dppm)2]X with [Pd2R2(μ-Cl)2(AsPh3)2], followed by treatment with NaBH4. The complexes were characterized by elemental analysis, 1H and 31P NMR spectroscopy. The solid-state structures of [Pd2(C6H4Me-4)2(μ-H)(μ-dppm)2]BH3CN (1a) (obtained as its BH3CN− salt when NaBH3CN was used instead of NaBH4), [PdPt(C6H4Me-4)2(μ-H)(μ-dppm)2]PF6 (2a), [Pd2(Mes)Et(μ-H)(μ-dppm)2]PF6 (3b), [Pd2(Mes)Ph(μ-H)(μ-dppm)2]PF6 (3c) and [EtPt(μ-H)(μ-dppm)2PdMe]PF6 (4) have been determined by X-ray crystallography. 3c adopts an elongated boat conformation in the solid state, whereas the others exist in the chair form. The unsymmetrical cations 2a and 4 containing smaller organic substituents are disordered in the solid state, whereas the mesityl-containing derivatives 3b and 3c are not.

Modifier effects in the determination of arsenic, antimony and bismuth by electrothermal atomic absorption spectrometry

The effect of palladium, mixed palladium–magnesium and magnesium modifiers on the determination of arsenic, antimony and bismuth was tested. It was found that palladium modifier works correctly only in nitric acid solution. If the sample solution contains hydrochloric acid then palladium becomes a strong interferent and causes significant losses of the analyte. For arsenic and antimony, but not for bismuth, this shortcoming may be eliminated by use of mixed palladium–magnesium or magnesium modifier. Magnesium modifier was found to be superior to the mixed modifier since it is able to eliminate also the negative effects of perchloric acid and of the iron group elements. It is, however, completely ineffective in relation to bismuth when used individually or in a mixture with palladium. Palladium may be used as a modifier for the determination of antimony and bismuth in hydrochloric acid solution only when it is preliminarily reduced to the metal form. The mechanism of the modifier activity is discussed.

Enthalpies of formation of BaPdS 2 and LaPd 3S 4

The BaPdS 2 mixed palladium sulfide has been synthesized by direct reaction of a stoichiometric mixture of the PdS and BaS binary constituent sulfides. The standard molar enthalpies of formation of BaPdS 2 and LaPd 3S 4 mixed sulfides were determined by the method of direct reaction calorimetry through synthesizing the respective compounds in a calorimetric cell from the stoichiometric mixture of appropriate starting materials. Combining the experimental results with the reference data for the starting materials, we found Δ f,298 H 0 m(BaPdS 2)=−515.4±16.8 kJ mol −1; and Δ f,298 H 0 m(LaPd 3S 4)=−817.6±43.8 kJ mol −1.

Mixed Palladium(iii)–Nickel(ii) and Palladium(ii)–Copper(ii) Complex Salts with Biuret and the N4-Macrocycle Cyclam

Three paramagnetic mixed salts of palladium(III) and palladium(II) complexes with biuret and Cu(cyclam)2+ or Ni(cyclam)2+ are obtained and their magnetic properties studied.