Interaction of palladium(II) with DL-selenamethionine in acidic aqueous solution

Summary The interaction of Pd^II with DL-selenamethionine (SeMet) in acidic aqueous solution was investigated. SeMet was found to act as a bidentate ligand, forming a stable complex with Pd^II. Binding of the metal ion to the selenoether group creates a new chiral centre, which generates two sets of¹H and¹³C n.m.r. methyl resonances for the two diastereoisomers. The²J values for (⁷⁷Se–Me) decreased upon complex formation.     

Suzuki cross-coupling reactions catalyzed by palladium nanoparticles in aqueous solution

Palladium nanoparticles stabilized by poly(N-vinyl-2-pyrrolidone) (PVP) are efficient catalysts for the Suzuki reactions in aqueous medium. The time dependence of the fluorescence intensity of the biphenyl product in the reaction between iodobenzene and phenylboronic acid is used to determine the initial rate of the catalytic reaction. The initial rate depends linearly on the concentration of Pd catalyst, suggesting that the catalytic reaction occurs on the surface of the Pd nanoparticles.     

The thermal decomposition of aqueous manganese (II) nitrate solution

The thermal decomposition of commercially available aqueous solutions of manganese(II) nitrate was investigated using the conventional thermal analytical techniques of thermogravimetry (TG), differential thermal analysis (DTA), and evolved gas analysis (EGA). Infrared spectra and X-ray diffraction patterns were used to help characterize intermediate species.     

PMR studies of palladium(II)-glycyl-L-aspartic acid complexes in aqueous solution

The PMR technique has been used to establish the coordinations in 1 : 1 and 1: 2 Pd(II) to glycyl-L-aspartic acid complexes. In the 1 : 1 complex both nitrogens and the α-carboxyl group are coordinated to the metal ion and the β-carboxyl group is in a pseudoaxial position. In the 1 : 2 complex only nitrogen atoms are coordinated to Pd(II) ions and the conformations of the ligands in this complex are also established.     

Synthesis and characterization of gold nanoparticles stabilized by palladium(II) phosphine thiol

This work is focused on the synthesis of innovative hybrids made by linking gold nanoparticles to protected organometallic Pd(II) thiolate. The organometallic protected Pd(II) thiolate, i.e. trans-thioacetate-ethynylphenyl-bis(tributylphosphine)palladium(II) has been synthesized, in situ deprotected and linked to Au nanoparticles. In this way new hybrid, with a direct link between Pd(II) and Au nanoparticles through a single S bridge, has been isolated. The combination of the organometallic Pd(II) thiol with gold nanoparticles allows the enhancement and tailoring of electronic and optical properties of the new organic-inorganic nano-compound. Single-crystal gold nanoparticles, uniform in shape and size were obtained by applying a modified two-phase method (improved Brust-Schiffrin reaction). In addition, the chemical environment of the Au nanoparticles was investigated and a covalent bonding between Au nanoparticles and the organometallic thiols was observed.     

Synthesis of palladium nanoparticles by reaction of filamentous cyanobacterial biomass with a palladium(II) chloride complex

The interaction of cyanobacterial biomass (Plectonema boryanum UTEX 485) with aqueous palladium(II) chloride (PdCl2 degrees ) has been investigated at 25-100 degrees C for up to 28 days. We report that the release of organic materials from the cyanobacteria promoted the precipitation of Pd(0) as crystalline spherical and elongate nanoparticles (< or =30 nm), both in solution and as dispersed and encrusted nanoparticles on cyanobacterial cells. In contrast, under abiotic conditions at 100 degrees C, palladium hydride (PdHx) was the principal palladium phase precipitated, with only minor amounts of palladium metal.     

Composition,properties, and structure of palladium(II) chlorides in aqueous solution

The composition, stability, and structure of palladium(II) chloride complexes in hydrochloric acid media have been determined using nuclear-magnetic relaxation, magnetochemical methods, and Rayleigh light scattering. The predominant form in solution for palladium(II) concentrations greater than 0.005 moles/liter is the octahedral Pd₆Cl₁₂ or Pd₆Cl₁₄ ^2–, which has antiferromagnetic properties in contrast with the paramagnetic properties of the mononuclear aquachloride. The polarizability anisotropy of Pd-Cl bonds with terminal and bridging chlorine atoms has been determined.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2473–2477, November, 1990.     

Bonding modes of nitrite and nitrate in palladium(II) and platinum(II) complexes

The crystal structures of the well-known complexes, [(Me₄en)M(II)X₂] (Me₄en?=?N,N,N??,N??-tetramethylethylenediamine; M(II)?=?Pd(II) or Pt(II); X ^??=?NO₂ ^? or NO₃ ^?) have been determined. For [(Me₄en)Pd(NO₂)₂] and [(Me₄en)Pt(NO₂)₂], the nitrite anion acts as a monodentate N-donor ligand in the solid state. In contrast, for [(Me₄en)Pd(ONO₂)(O₂NO)], the two nitrate anions act as a monodentate O-donor (ONO₂) and a bidentate O,O??-donor (O₂NO). Recrystallization of [(Me₄en)Pt(NO₃)₂] from Me₂SO yields the Me₂SO adduct with a monodentate O-donor nitrate and a counteranionic nitrate, [(Me₄en)Pt(ONO₂)(S-Me₂SO)](NO₃). The solution behavior of these complexes, including the equilibrium between coordinated and free Me₂SO, has been investigated.     

Synthesis of 1,3-bis-(5-ferrocenylisoxazole-3-yl) benzene-derived palladium(II) acetate complex and its application in Mizoroki-Heck reaction in an aqueous solution

The first synthesis and characterization of 1,3-bis-(5-ferrocenylisoxazole-3-yl) benzene-derived palladium(II) acetate complex were described and its application in Heck coupling reactions in an aqueous solution was studied. Complex 5 had been demonstrated to be a highly stable, active and efficient catalyst for Mizoroki-Heck coupling reactions.     

Microwave-assisted aqueous Suzuki coupling reactions catalyzed by ionic palladium(II) complexes

Suzuki coupling is one of the most powerful methods for the synthesis of biaryls. We have prepared and characterized a series of unsymmetrical sulfonated water-soluble Pd(II)-pyridyl imine complexes and investigated them as catalysts for the Suzuki cross-coupling reaction in water under microwave irradiation. The compounds proved to be effective catalysts.     

Binding of hexacyanoferrate(II) by aliphatic amines in aqueous solution

The stability of hexacyanoferrate(II)-amine(methylamine, ethylenediamine, diethylenetriamine and tetraethylenepentamine) was determined potentiometrically. Species Fe(CN)₆(A)H _j ^(j–4) (A=amine) are formed in all the systems investigated, with j=1...n+2 (n=number of aminogroups). Some other complexes Fe(CN)₆(A)_iH_j (with i>1) were also found. The stability of these complexes is fairly high: the full protonated amine species, show for the reaction Fe(CN)₆ ^4- + H_nAⁿ⁺ = Fe(CN)₆(A)H_n ^(n-4) an equilibrium constant given by logK=0.686+2.10n. Factors affecting the stability are discussed in comparison with similar systems, together with the importance of interferences.     

Variation dynamics of palladium(II) and tin(II) concentrations in activating solution

A study of the possibility of optimizing the efficiency of a catalytic palladium layer demonstrated that the minimum palladium adsorption providing a sufficient catalytic activity of the surface is Γ_min = 3.178 × 10^–6 mol m^–2, which can be reached at a palladium dichloride concentration of 0.035 g L^–1. It was shown that palladium(II) activates the surface of the insulator (is sorbed) from a true, rather than a colloid solution.     

Copper(II) ion hydrolysis in aqueous solution

A copper(II) ion-selective-electrode potentiometric method was used to determine the first and second hydrolysis constants of Cu²⁺. Special techniques prevented copper(II) hydroxide precipitation, and copper(II) carbonate and cipper(II) organic complexation during the titration of the experimental solution over the pH range 6.8–8.4. The large change in the total copper concentration during the titration due to adsorption of copper onto the vessel walls was accounted for by measuring the total copper concentration at each pH by atomic absorption spectrophotometry. The two hydrolysis constants were determined at 25°C in 0.7 and 0.05m NaClO₄ media. The measured stability constants are independent of the copper concentration and yield similar zero ionic strength values. Also, the stepwise equilibrium constants decrease as the ligand number increases.     

Synthesis of aluminum oxide nanoparticles in an aqueous ammonium-formaldehyde solution

A method of synthesis of the organic-inorganic nanocomposite consisting of a paraformaldehyde matrix and aluminum oxide nanoparticles is developed. Spontaneous dispersion of the composite in water at various component ratios makes it possible to prepare a sol or gel of hydrated aluminum oxide. No changes in the oxide particle dimensions are observed during storage of the composite.     

Synthesis of iron nanoparticles via chemical reduction with palladium ion seeds

We report on the synthesis of highly monodisperse iron nanoparticles, using a chemical reduction method. Iron nanoparticles with an average diameter of 6 nm and a geometric standard deviation of 1.3 were synthesized at a pH of 9.50 from ferric chloride precursor with sodium borohydride as the reducing agent, polyacrylic acid as the dispersing agent, and palladium ions as seeds for iron nanoparticle nucleation. The resulting nanoparticles were ferromagnetic at 5 K and superparamagnetic at 350 K. The dispersing agent polyacrylic acid (PAA) was shown to prevent iron nanoparticles and possibly palladium clusters from aggregating; in the absence of PAA, only aggregated iron nanoparticles were obtained. The addition of palladium ions decreased the diameter of iron nanoparticles presumably by providing sites for heterogeneous nucleation onto palladium clusters. In the absence of palladium ions, the mean diameter of iron nanoparticles was approximately 110 nm and the standard deviation increased to 2.0. The pH of the solution also was found to have a significant effect on the particle diameter, likely by affecting PAA ionization and altering the conformation of the polymer chains. At lower pH (8.75), the PAA is less ionized and its ability to disperse palladium clusters is reduced, so the number of palladium seeds decreases. Therefore, the resulting iron nanoparticles were larger, 59 nm in diameter, versus 6 nm for nanoparticles formed at a pH of 9.50.     

Copper (II) adsorption from aqueous solution by herbaceous peat

In this research, the herbaceous peat collected from Gavurgolu peatlands, one of the biggest Turkish peatlands, was utilized as an adsorbent for the removal of copper (II) ions from aqueous solution. Adsorption experiments were conducted under various conditions, i.e., initial concentration, temperature, and pH. While the amount of Cu (II) adsorbed on the peat increased with increasing concentration of Cu (II) ions, it was not markedly affected by temperature and pH. Percentage removal was higher at lower concentration. For example, the maximum percentage removal of Cu (II) ions for initial concentration of 3 x 10(-4) M was 97.04% at 21 degrees C and pH 5.5. The adsorption capacity (Q(0)) of the peat was 4.84 mgg(-1) from Langmuir adsorption isotherm for the concentration range of 3 x 10(-4)-6 x 10(-4) M at 21 degrees C and pH 5.5. The equilibrium time of adsorption of Cu (II) ions was 150 min and independent of concentration and temperature. The amount of Cu (II) adsorbed at equilibrium time did not considerably change with temperature and pH. It was also determined that adsorption isotherm followed both Freundlich and Langmuir. Uptake mechanism of Cu (II) ions by the peat occurs via cation exchange (especially by means of Ca(2+) and Mg(2+)) as well as copper/peat complexation. Adsorption kinetic was consistent with the pseudo-second-order model.     

Synthesis of palladium(II) and nickel(II) complexes with tetrabenzoporphine

Palladium and nickel complexes with tetrabenzoporphine were synthesized by reacting tetrabenzoporphine and cadmium tetrabensoporphine with palladium and nickel chlorides in boiling dimethylformamide and identified.     

γ-Induced reduction of Eu(III) in aqueous solution

-radiation of Co⁶⁰ has been applied to reduce Eu(III) to Eu(II) in aqueous solutions of the mixture of rare earths. The kinetics of the process has been investigated as a function of the absorbed radiation dose and organic additive concentration.

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+3 - Co⁶⁰: Eu(III)Eu(II). .