Potentiometric determination of silver(I), palladium(II) and gold(III) in mixtures by use of an iodide-selective electrode

Two procedures are proposed for the potentiometric determination of Ag(I), Pd(II) and Au(III) in binary mixtures, by titration with potassium iodide solution, and use of a commercial iodide electrode as sensor. In the first procedure, two aliquots of the mixture are titrated, at pH 2.0 ± 0.2 and 9.0 ± 0.2, adjusted with dilute sulphuric acid and ammonia solution. At pH 2.0, the titrant reacts with both metals, whereas at pH 9.0, Ag(I) is the only reactant. The second procedure utilizes titration of two aliquots of the mixture in the presence and absence of a selective masking agent. The methods have been applied to the determination of these metals in some jewellery alloys.     

Catalytic amperometric and catalytic constant-current potentiometric titrations of silver(I), palladium(II) and mercury(II)

Amperometry and constant-current potentiometry were used to follow the course of catalytic titrations of silver(I), palladium(II), and mercury(II) with potassium iodide. The Ce(IV)As(III) and Ce(IV)Sb(III) systems in the presence of sulphuric acid were used as indicator reactions. The possibilities of application of platinum, palladium, gold, graphite, and glassy-carbon indicator electrodes were investigated. Graphite appeared to be somewhat more advantageous than the other electrode materials. The effect of concentration of the components of the indicator reactions, the presence of organic solvents and acids on the shape of the catalytic titration curves was studied. Amounts of 30-3000 mug of silver(I) nitrate, 90-900 mug of palladium(II) chloride, 130-1300 mug of mercury(II) chloride, and 150-1500 mug of mercury(II) nitrate were determined with a relative standard deviation less than 1.0%. The results obtained were in good agreement with those of comparable methods. The catalytic titration method developed was applied to determination of mercury in Unguentum Hydrargyri.     

Structure and dynamics of tetrakis(thiophosphinato)resorcinarene complexes of silver(I), gold(I), and palladium(II)

The coordination chemistry of the tetrakis(thiophosphinato)resorcinarene sulfur-donor ligands [(C6H2CH{CH2CH2Ph})4{OC(O)R}4{OP(=S)Ph2}4] (L), where R = OCH2Ph, 4-C6H4CH3, C6H11, C4H3S, or OCH2CCH, is reported. Both silver(I) and gold(I) form cationic complexes of the type [LM2]2+, in which the ligand acts as a bis(chelate) in forming complexes with linear S-M-S (M = Ag or Au) stereochemistry. Gold(I) also forms the unusual complex [L(AuCl)2][LAu2]2+, which forms a supramolecular polymer through intermolecular aurophilic attractions. Palladium(II) forms the complex [LPd2Cl2(mu-Cl)2], in which the dipalladium(II) unit extends the natural bowl structure of the resorcinarene. The solid-state and solution conformations of the complexes, as determined by X-ray structure determination and NMR spectroscopy, respectively, are similar, but several complexes were found to exhibit dynamic behavior in solution, involving either conformational mobility of the resorcinarene unit or intermolecular ligand exchange.     

Pyrrole-appended derivatives of O-confused oxaporphyrins and their complexes with nickel(II), palladium(II), and silver(III)

Condensation of 2,4-bis(phenylhydroxymethyl)furan with pyrrole and p-toluylaldehyde formed, instead of the expected 5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-21-carbaporphyrin, a pyrrole addition product [(H,pyr)OCPH]H(2); this product can formally be considered as an effect of hydrogenation of 3-(2'-pyrrolyl)-5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-21-carbaporphyrin ([(pyr)OCPH]H). The new oxacarbaporphyrinoid presents the (1)H NMR spectroscopy features of an aromatic molecule, including the upfield shift of the inner H21 atom. Insertion of NiCl(2) or PdCl(2) into [(H,pyr)OCPH]H(2) gave two structurally related organometallic complexes, [(pyr)OCP]Ni(II)] and [(pyr)OCP]Pd(II)], in which the metal ions are bound by three pyrrolic nitrogens and the trigonally hybridized C21 atom of the inverted furan. The reaction of [(H,pyr)OCPH]H(2) with silver(I) acetate yields a stable Ag(III) complex [(C(2)H(5)O,pyr)OCP]Ag(III)] substituted at the C3 position by the ethoxy and pyrrole moieties. The macrocyclic frame of [(H,pyr)OCPH]H(2) is conserved. Addition of trifluoroacetic acid to [(C(2)H(5)O,pyr)OCP]Ag(III)] yielded a new aromatic complex [(pyr)OCP]Ag(III)](+). The structures of [(pyr)OCP]Ni(II)] and [(C(2)H(5)O,pyr)OCP]Ag(III)] have been determined by X-ray crystallography. In both molecules the macrocycles are only slightly distorted from planarity and the nickel(II) and silver(III) are located in the NNNC plane. The dihedral angle between the macrocyclic and appended-pyrrole planes of [(pyr)OCP]Ni(II)] reflects the biphenyl-like arrangement with the NH group pointing out toward the adjacent phenyl ring on the C5 position. Tetrahedral geometry around the C3 atom was detected for [(C(2)H(5)O,pyr)OCP]Ag(III)]. The Ni[bond]C and Ag[bond]C bond lengths are similar to other nickel(II) or silver(III) carbaporphyrinoids where the trigonal carbon atom coordinates the metal ion. The trend detected in the (13)C chemical shifts for the appended-pyrrole resonances has been rationalized by the extent of effective conjugation between the macrocycle and the appended pyrrole moiety controlled by the hybridization of the C3 atom and the metal ion oxidation state. The dianionic or trianionic macrocyclic core of the pyrrole-appended derivatives is favored to match the oxidation state of nickel(II), palladium(II), or silver(III), respectively.     

Spectrophotometric microdetermination of copper(II), silver(I), and gold(III) using azastyrene Schiff bases

A new method for the spectrophotometric microdetermination of Cu(II), Ag(I), and Au(III) using β-2-hydroxybenzyl-5-bromo- (I_a), 5-chloro- (I_b), and 3-methoxy-2-hydroxyazastyrene (I_c) is given. The optimum conditions favoring the formation of the colored complexes are extensively studied. The molecular structure was found to be (1:1) and (1:2) (M:L). Beer's law is obeyed up to 5.00, 8.64, and 11.82 ppm for Cu(II), Ag(I), and Au(III), respectively, while the optimum concentration ranges using the Ringbom method are 0.6–5.00, 1.00–8.60, and 2.00–11.80 ppm for the same metal ions, respectively.     

Sorption properties of the complex-forming sorbent bis-1,3,5-dithiazinanee-5-yl-ethane with respect to palladium(II), silver(I), and mercury(II)

Sorption properties of the weakly basic complex-forming sorbent bis-1,3,5-dithiazinane-5-yl-ethane with respect to Pd(II), Ag(I), and Hg(II) were studied. The sorbent was prepared from ethylenediamine, formic aldehyde, and H₂S by a single-reactor procedure.     

Preconcentration of silver(I), gold(III) and palladium(II) in sea water with p-dimethylaminobenzylidenerhodanine supported on silica gel

A water-insoluble chelating material, p-dimethylaminobenzylidenerhodanine on silica gel (DMABR—SG) is described for preconcentration of trace amounts of silver(I), gold(III) and palladium(II) from water samples. Radioactive tracers (^110mAg and ¹⁹⁵Au) were used to study the behavior of silver and gold; palladium was monitored spectrophotometrically as its 1-(2-pyridylazo)naphthol complex in chloroform. In batch experiments, silver was quantitatively retained on the DMABR—SG at acidities ranging from 1.7 M to pH 5, and gold from 3 M to pH 5; equilibrium was achieved within 1 min for both elements. From sea water, silver ion was completely retained at pH 1.0–6.5 and gold ion at pH 1.0–3.5. In the case of palladium, shaking for about 20 min was required for quantitative retention at pH 1.0–5.0 for aqueous solution and at pH 1.0–7.0 for sea water. The chelating capacity of the DMABR—SG was 23 μmol Ag, 11 μmol Au and 11 μmol Pd per g. Quantitative recovery of silver and gold on DMABR—SG columns from sea water was achieved at higher flow rates (1–2 l h^-1 and 2–3 l h^-1, respectively) than with other chelating resins, e.g., Chelex 100, palladium required slower flow rate (150 ml h^-1). Silver retained on the DMABR—SG column was completely eluted with 20 ml of 2.5% sodium thiosulfate solution but palladium remained on the column. Silver, gold and palladium were quantitatively eluted with 20 ml of 0.1% thiourea in 0.1 M hydrochloric acid.     

Polythiophene-coated Fe3O4 nanoparticles as a selective adsorbent for magnetic solid-phase extraction of silver(I), gold(III), copper(II) and palladium(II)

We have developed a fast method for sensitive extraction and determination of the metal ions silver(I), gold(III), copper(II) and palladium(II). Fe₃O₄ magnetic nanoparticles were modified with polythiophene and used for extraction the metal ions without a chelating agent. Following extraction, the ions were determined by flow injection inductively coupled plasma optical emission spectrometry. The influence of sample pH, type and volume of eluent, amount of adsorbent, sample volume and time of adsorption and desorption were optimized. Under the optimum conditions, the calibration plots are linear in the 0.75 to 100 μg L^?1 concentration range (R²?>?0.998), limits of detection in the range from 0.2 to 2.0 μg L^?1, and enhancement factors in the range from 70 to 129. Precisions, expressed as relative standard deviations, are lower than 4.2 %. The applicability of the method was demonstrated by the successful analysis of tap water, mineral water, and river water.

Addition of protic molecules to coordinated 2-pyridinecarboxaldehyde in gold(III), palladium(II), and platinum(II) complexes

The reactions of Au^III, Pt^II and Pd^II complexes with 2-pyridinecarboxaldehyde (2CHO-py) have been examined in protic (H₂O, MeOH, EtOH) and aprotic (DMF, CH₂Cl₂) solvents. Compounds in which the pyridine ligand is N-coordinated, either in the original aldehydic form or in a new form derived from addition of one or two protic molecules, have been isolated, namely: [Au(2CHO-py · H₂O)Cl₃], [Au(2CHO-py · MeOH)Cl₃], [Au(2CHO-py · 2EtOH)Cl₃], cis-[Pt(2CHO-py)₂Cl₂], trans-[Pd(2CHO-py)₂Cl₂], trans-[Pt(dmso)(2CHO-py)Cl₂], [Pt{C₅H₄N-(CH₂SMe)}Cl(2CHO-py)](ClO₄), [Pt(terpy)(2CHOpy)](ClO₄)₂, [Pt(terpy)(2CHO-py · H₂O)](ClO₄)₂ (terpy = 2,2′:6′,2′′-terpyridine). ¹H-n.m.r. experiments show that the addition of the protic molecule(s) to the Pt^II and Pd^II complexes is reversible. The effects of the nature of the metal ion and the ancillary ligands as well as of the total charge of the complexes on the relative stability of the addition products are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Rhodanine complexes of zinc(II), cadmium(II), mercury(II) and mercury(I)

The following rhodanine (HRd) complexes of zinc(II), cadmium(II), mercury(II) and mercury(I) have been prepared and studied by i.r. spectra: M(Rd)₂(NH₃)₂ (MZn, Cd) with a 4N,2S-six-coordination; Zn₃(Rd)₄(CH₃COO)(OH), Cd₂(Rd)₃(HRd)₃(CH₃COO)(H₂O) in which the acetato anion is bicoordinated; Hg(Rd)₂, Hg₂(HRd)₃(BF₄)₂·0.5(HAc or EtOH), Hg(HRd)(CF₃COO)₂·H₂O in which both the ligands HRd and Rd⁻ are S,N-bonded to the metal; Hg(HRd)₂Cl₂, Hg(HRd)₄(ClO₄)₂ in which the ligand HRd is S-bonded; Hg₃(Rd)₃ · NH₃ with S,N-bonded Rd⁻ ligand.     

Bis(ethylene)dithioformamidinium dihalides and their copper(I), silver(I) and gold(I) complexes

The bis(ethylene)dithioformamidinium dihalides (En₂Tu₂X₂, X = Cl(H₂O), Br, I), obtained by oxidation of ethylenethiourea, and their complexes MX.En₂Tu₂X₂ (M = Cu, X = Br[0.2 DMF]; M = Ag, X = Br; M = Au, X = Cl), 2MX. 1.5 En₂Tu₂X₂ (M = Cu, X = Cl[0.4 DMF]; M = Ag, X = I), MX. 1.5 En₂Tu₂X₂ (M = Cu, X = I; M = Au, X = Br), AgCl. 1.25 En₂Tu₂Cl₂, 4AgI. 1.5 En₂Tu₂I₂, AuI.2En₂Tu₂I₂, were prepared and studied by i.r. spectroscopy. The En₂Tu²⁺₂ ion is N-bonded to the metal ion. Some νMN and νMX bands are tentatively assigned.     

The extraction of mercury(II), silver(I), cobalt(II) and cadmium(II) by dioctylarsinic acid in chloroform

Dioctylarsinic acid (HDOAA) in chloroform solution has been investigated as a reagent for the extraction of Hg(II), Ag(I), Co(II), and Cd(II). Silver, cobalt and cadmium are not extracted below pH 7. An extraction coefficient of 1.1, constant over the pH range 1–6.5, was observed for Hg(II). With HCl concentrations of 1–8 M the extractability of mercury decreased slowly, reaching E_a⁰ = 0.05 at 8 M HCl. Silver formed a silver dioctylarsinate precipitate which collected at the interface. The extraction coefficients for Hg(II), Co(II) and Cd(II) increased above pH 7 to values of 20 (pH 9.1), 30 (pH 8.0), and 23 (pH 10), respectively. Reagent- and pH-dependence studies indicated that Co(II) and Cd(II) are extracted as M(DOAA)₂ or M(DOAA)Cl through interaction of HDOAA with M(OH)₂ or M(OH)⁺. Mercury was extracted from solutions of pH 1–6.5 as HgCl₂ (HDOAA)_2.5.     

Reactivity and stability of organocopper(I), silver(I), and gold(I) ate compounds and their trivalent derivatives

Organocuprate (R(2)Cu(-)) reagents react with a carbon electrophile to form a new C-C bond, yet their silver and gold counterparts seldom serve for such purposes. The origin of this striking difference is discussed with the aid of the quantum mechanical calculations using hybrid density functional method. The copper reaction takes place through two steps, the nucleophilic reaction of the ate complex R(2)Cu(I)(-) with an electrophile E(+) and the decomposition of the resulting R(2)(E)Cu(III) intermediate. These two steps were examined for Cu, Ag, and Au to find the reasons for the superiority of organocopper compounds to the silver and the gold counterparts. The first reaction is favored because of the higher-lying d-orbitals that directly participate in the nucleophilic reaction. The second reaction is faster with copper because of the intrinsic instability of the high valent copper species.     

Synthesis and characterization of silver(I), gold(I), and gold(III) complexes bearing a bis-dialkylamino functionalized N-heterocyclic carbene

Bis-1,3-[2-(diisopropylamino)ethyl]-imidazolium chloride, 1, has been prepared and used as a precursor for the synthesis of the corresponding silver(I) chloride complex 2. The single crystal structure analysis reveals that the complex dimerizes in the solid state. Transmetalation of 2 with (tht)AuBr (tht = tetrahydrothiophene) yields the (NHC)Au(I)Br complex 3. By treatment with bromine it is oxidized to (NHC)AuBr₃, 4, which is obtained as a yellow, microcrystalline powder. The UV-vis spectra of 4 are dependent on the pH-value and suggest a square-pyramidal structure in solution.     

Keto sulfides derived from tert-dodecyl mercaptan and their extractive power with respect to palladium(II) and gold(III)

γ-Keto sulfide concentrates were prepared by alkylthiomethylation of propanone, butanone, and acetophenone with technical-grade tert-dodecyl mercaptan and other sulfur-containing substances, and their extractive power with respect to palladium(II) and gold(III) from hydrochloric acid solutions (chloroform as diluent) was studied.     

Coordination chemistry of silanedithiolato ligands derived from cyclotrisilathiane: synthesis and structures of complexes of iron(II), cobalt(II), palladium(II), copper(I), and silver(I)

The coordination chemistry of chelating silanedithiolato ligands has been investigated on Fe(II), Co(II), Pd(II), Cu(I), and Ag(I). Treatment of M(OAc)(2) (M = Fe, Co, Pd) with cyclotrisilathiane (SSiMe(2))(3) in the presence of Lewis bases resulted in formation of Fe(S(2)SiMe(2))(PMDETA) (1), Fe(S(2)SiMe(2))(Me(3)TACN) (2), Co(S(2)SiMe(2))(PMDETA) (3), and Pd(S(2)SiMe(2))(PEt(3))(2) (4) (PMDETA = N,N,N',N',N' '-pentamethyldiethylenetriamine; Me(3)TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane). The analogous reactions of M(OAc) (M = Cu, Ag) in the presence of PEt(3) gave rise to the dinuclear complexes M(2)[(SSiMe(2))(2)S](PEt(3))(3) [M = Cu (5), Ag (6)]. Complexes were characterized in solution by (1)H, (31)P[(1)H], and (29)Si[(1)H] NMR and in the solid state by single-crystal X-ray diffraction. Mononuclear complexes 1-3 have a four-membered MS(2)Si ring, and these five-coordinate complexes adopt trigonal-bipyramidal (for the PMDETA adducts) or square-pyramidal (for the Me(3)TACN adduct) geometries. In dimer 6, the (SSiMe(2))(2)S(2)(-) silanedithiolato ligand bridges two metal centers, one of which is three-coordinate and the other four-coordinate. The chelating effect of silanedithiolato ligands leads to an increase in the stability of silylated thiolato complexes.     

The Fourier transform Raman spectra of a series of platinum(II), palladium(II) and gold(III) square-planar complexes

The Fourier transform Raman spectra of solid samples and some D₂O solutions, of complexes of formula K_nMX₄, M = Pt(II), Pd(II), and Au(III); X = Cl and Br are reported. It was found that the spectra of the tetrabromides contain more bands than the corresponding tetrachlorides; this indication that the two halides have different crystal structures is discussed. Fourier transform Raman spectra of M(NH₃)₄Cl₂ M = Pt(II), and Pd(II), trans- and cis-Pt(NH₃)₂Cl₂ (i.e. the pharmaceutical product “cis-platin”), and trans-Pd(NH₃)₂X₂, X = Cl and Br are also reported here and the significance of the spectra discussed. Although many of these spectra have been reported earlier the quality of the new Fourier transform data is superior to that in the literature.     

Solvation of gold(III) chloride with tris(2-ethylhexyl) phosphate and separation from palladium(II), platinum(IV), lead(II) and copper(II)

Summary Gold can be extracted from HCl solution by means of tris(2-ethylhexyl)phosphate and in this way be separated from Pd, Pt, Pb and Cu. Recoveries better than 99% have been achieved. The determination is carried out by the stannous chloride method.     

Pentafluorophenylthiolate derivatives of ruthenium(II), rhodium(I) and palladium(II)

Summary The pentafluorophenylthiolate anion [C₆F₅S]^– reacts with chloro-bridged binuclear complexes of Ru^II, Rh^I and Pd^II to give the compounds [(N-N)(PPh₃)₂Ru(SC₆F₅)]₂Cl₂ (1) (N-N = bipyridine), [LRh(SC₆F₅)]_n (L = cycloocta-1,5-diene (2) or norbornadiene (3), n = 2 and L = dicyclopentadiene (4) for which n is probably 4), [(PPh₃)Pd(SC₆F₅)Cl]₂ (5) and (MeS-CHMeCHMeSMe)Pd(SC₆F₅), (6).¹⁹F n.m.r. spectroscopy shows a variable number of isomers depending on the compound considered.