Interaction of Silver(II) and Gold(III) meso-Tetraphenylporphine Complexes with Concentrated Sulfuric Acid

The reaction of meso-tetraphenylporphine (H₂TPP) with Ag(OAc) or KAuCl₄in boiling acetic acid affords Ag^IITPP and (Cl)Au^IIITPP complexes. The complexes are purified by column chromatography and identified by thin layer chromatography and IR and electronic absorption spectroscopy. The transfer of a proton to the porphyrin macrocycle and dissociation of the complexes via the metal–nitrogen bonds in concentrated H₂SO₄at different temperatures and H₂SO₄concentrations are studied by spectrophotometric and kinetic methods. The formation of the stable ion-molecular H-associate of the metalloporphyrin with a doubly-charged metal cation is found for the first time for silver(II) tetraphenylporphine. Gold(III) tetraphenylporphine exists in a sulfuric acid solution in the monomolecular form. The numeric values of true rates and activation parameters of the complex dissociation are determined. The stability, state in solution, and mechanism of dissociation of the silver(II) and gold(III) tetraphenylporphine complexes are determined by the metal electronic configuration of the complex cation and, especially, by the contribution of the component to the donor–acceptor M–N interaction.     

Simultaneous determination of uranium(IV) and iron(II) with a stopped-flow inductive kinetic spectrophotometric method

A kinetic method for simultaneous determination of multielements is proposed, and a procedure for simultaneous determination of uranium(VI) and iron(II) is established based on their inductive effect on the chromium(VI)-iodide redox reaction in weak acidic medium. The reaction was monitored with the stopped-flow spectrophotometric technique by using I ₃ ^– -starch complex as indicator. The calibration graphs are linear for 0–3.6 g.cm^–3 U(IV), and 0–2.5 g.cm^–3 Fe(II), respectively. Most foreign ions, except for V(IV), Sb(III), do not interfere with the determination.     

A microelectrode study of the mechanism of the reactions of silver(II) with manganese(II) and chromium(III) in sulphuric acid

The variation of the steady state limiting current for the Ag(I)/Ag(II) oxidation wave with the radius of the microdisc electrode, concentration and temperature has been used to probe the kinetics and mechanisms for the reactions of silver(II) with manganese(II) and chromium(III) in 10 mol dm⁻³ sulphuric acid. It is shown that the current density for the silver(I) mediated oxidation of manganese(II) is controlled by the diffusion of manganese(II) to the surface except for microelectrodes with radii below 5 μm. On the other hand, the current density for the mediated oxidation of chromium(III) is determined by the rate of the Ag(II)/Cr(III) reaction over a range of conditions. In contrast to the Ag(II)/water reaction, its kinetics can be fitted to a mechanism where the initial electron transfer from Cr(III) to the Ag(II) is the rate determining step.     

Re(III) complexes in the synthesis of platinum acetate complexes and the structure of [PPh3Pt(OAc)2]2

Reaction of tetrachlorodiacetatodirhenium dihydrate with triphenylphosphineplatinum (II) triacetatoargentate(I) produces a new binuclear platinum complex with acetate bridges, bis[(²-acetato)acetatotriphenylphosphine]diplatinum(II). The new complex is characterized by x-ray structural analysis, IR, and PMR spectroscopies. The Re(III) complex in this reaction is not only the source of chloride ions, which are necessary for precipitation of silver, and the acetate acceptor, but also the silver(I) reductant which is oxidized during the reaction to Re(IV).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1894–1899, August, 1989.     

Potentiometrische Manganbestimmung mit Kaliumhexacyanoferrat(III) in alkalischer Mannitl?sung

Zusammenfassung Zur potentiometrischen Manganbestimmung wird die Oxydation des Mangan(II)-Mannit-Komplexes mit Kaliumhexacyanoferrat(III) in alkalischer Lösung benutzt. Die Oxydation ist durch zwei gut ausgeprägte Potentialsprünge gekennzeichnet, die den Wertigkeitsübergängen Mangan(II) Mangan(III) und Mangan(III) Mangan(IV) entsprechen. Die Lösung soll 1 Mol/l KOH und 0,25–0,5 Mol/l Mannit enthalten. Der Konzentrationsbereich des bestimmbaren Mangans liegt zwischen 0,9 · 10^–3 und 2,3 · 10^–2 Mol/l.Die Bestimmung, die durch eine Reihe von Metallen nicht gestört wird, ist mit einem relativen Fehler von — 1% behaftet. Der störende Einfluß von Kobalt(II) wurde bis zu einem bestimmten Grad durch Zugabe von ÄDTA eliminiert, wobei nur ein gut meßbarer Potentialsprung auftritt, der der Oxydation Mangan(II) Mangan(IV) entspricht. Die Methode wurde mit guten Ergebnissen bei der Manganbestimmung im Schiefer und Kalkstein angewandt.

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Summary The oxidation of complexes of manganese (II)-mannitol with hexacyanoferrate(III) in alkaline medium was utilized for the potentiometric determination of manganese. The oxidation is characterized by 2 potential jumps belonging to the reactions manganese(II) manganese(III) and manganese(III) manganese(IV). The optimum medium is 1 Mol/l of KOH and 0.25–0.5 Mol/l of mannitol, concentration range of manganese being between 0.9×10^–3 and 2.3×10^–2 Mol/l. The presence of some metals does not influence the determination, the relative error being — 1%. The interfering influence of cobalt(II) is eliminated to a certain extent by the addition of EDTA. In this medium, only one potential jump belonging to the oxidation of manganese(II) manganese(IV) appears. The method yields good results when applied to slate and limestone.

     

Formation of uniform silver particles from bis (1,2-ethanediamine)silver(I) complex

Uniform spherical silver particles were produced by decomposing the bis(1,2-ethanediamine)silver(I) complex, by aging a solution of 1.0×10^–3 mole dm^–3 in silver (I) nitrate, 1.0 mole dm^–3 in 1,2-ethanediamine, and 2.5×10^–1 mole dm^–3 in nitric acid (basic solution) at 100°C for 42 min. The average modal diameter was estimated to be 0.52 m with a relative standard deviation of 0.10. A moderately oxygenrich layer, 40 Å thick, on the surface of the particles was detected by means of photoelectron surface microanalysis (XPS). The silver particles grew through a polynuclear-layer mechanism, as judged from the concentration change in soluble silver(I) species in the supernatant solution. The particles' point of zero charge (PZC) was estimated at pH 6.5 by potentiometric titration.     

A new spot test for cerium(IV) using triphenylmethane dyes

Summary A new sensitive and selective spot test for cerium(IV) using the triphenylmethane dyes, Erioglaucine A, Eriogreen B, Xylenecyanol FF, Setoglaucine O, and Setocyanine Supra, respectively, is described. The method consists of adding one drop of the dye solution (0.1%) to a drop of cerium(IV) solution, and then treating the mixture with sufficient amount of sulfuric, perchloric, or phosphoric acid to maintain the acidity at 6 to 9M. The colors produced with these dyes are: Erioglaucine A: orange, Eriogreen B: bright red, Xylenecyanol FF: orange yellow, Setoglaucine O: bright orange, and Setocyanine Supra: pink. The identification limit is 1 g in 1.5 ml, and the dilution limit is 11.5 · 10⁶ in all these cases. Many cations and anions do not interfere in the test, whereas reducing agents like Fe(II), Mo(V), U(IV), and hydroquinone, fluoride and EDTA interfere.

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Zusammenfassung Eine neue empfindliche und selektive Tüpfelnachweisreaktion für Cer(IV) mit den Triphenylmethanfarbstoffen Erioglaucin A (I), Eriogrün B (II), Xylolcyanol FF (III), Setoglaucin O (IV) bzw. Setocyanin Supra (V) wurde beschrieben. Man gibt einen Tropfen 0,1%ige Farbstofflösung zu einem Tropfen Cer(IV)-Lösung und behandelt die Mischung mit Schwefelsäure, Perchlorsäure oder Phosphorsäure, um 6 -bis 9-m Acidität zu erreichen. Die mit den genannten Farbstoffen erzielten Farbreaktionen sind: mit I orange, mit II leuchtend rot, mit IV leuchtend orange, mit III orange-gelb, mit V rosa. Die Erfassungsgrenze beträgt 1g/1,5 ml, die Grenzkonzentrationen in jedem Fall 11,5 · 10⁶. Viele Kationen und Anionen stören nicht, aber Reduktionsmittel wie Fe(II), Mo(V), U(IV), Hydrochinon sowie Fluorid und ÄDTA stören.

     

Redox properties of cobalt(II) and methylcobalt(III) complexes with dianionic macrocyclic polychelate ligands

Redox potentials of a series of complexes of cobalt(II) and organocobalt(III) with tetraazamacrocyclic (N₄) and N₂O₂-noncyclic polychelate ligands have been determined by cyclic voltammetry. Introduction of ano-phenylene fragment instead of an ethylene fragment into an equatorial ligand and/or exchange of an N₄-coordination chromophore for the N₂O₂-analog has been shown to result in the anodic shift of redox potentials of MeCo(IV)L/ MeCo(III)L, MeCo(III)L/MeCo(II)L, and Co(II)L/Co(I)L pairs. It has been established that the solvent effect on redox potential is larger for Co(III)L/Co(II)L than for other pairs. Apparently, this is the first case when quasi-reversible stages of oxidation of MeCo(III)L to MeCo(IV)L⁺ and MeCo(IV)L⁺ to [MeCo(IV)L]²⁺ can be simultaneously observed. A. relatively stable complex of methylcobalt(IV) with a long lifetime at 20 °C has been registered by the ESR method.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1029–1033, June, 1993.     

Oxovanadium(IV), manganese(II) and manganese(III) carbodithioates exhibiting abnormal magnetic behaviour

Summary New carbodithioate complexes of the oxovanadium(IV), manganese(II) and manganese(III) ions have been prepared and studied by i.r. and electronic spectral and variable temperature magnetic susceptibility (77K to room temperature) measurements. The carbodithioate ligands, 4-methylpiperazine-1-carbodithioate (4-MPipzcdt) and 4-phenylpiperazine-1-carbodithioate (4-PPipzcdt), were derived from heterocyclic secondary amines. The VO(4-MPipzcdt)₂ and VO(4-PPipzcdt)₂ complexes possess C _4v symmetry; Mn(4-PPipzcdt)₂ is tetrahedral and Mn(4-PPipzcdt)₃ is octahedral. All exhibit abnormal room temperature magnetic moments and the variable temperature magnetic moments suggest antiferromagnetism for the oxovanadium(IV) and the manganese(II) complexes and the occurrence of low spin (³ T _1g ) high spin (⁵ E _g ) equilibrium in addition to antiferromagnetic interactions in the manganese(III) complex. The spin-spin exchange parameter (-2J) value for the VO(4-MPipzcdt)₂ complex has been calculated using variable temperature magnetic susceptibility data.     

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.     

Kinetics and mechanism of silver(I) catalyzed oxidation of tris(1,10-phenanthroline)iron(II) with peroxodiphosphate in acetate buffers

A kinetic study of the silver(I)-catalyzed oxidation of tris(1,10-phenanthroline)iron(II) with peroxodiphosphate was carried out by estimating tris-complex at 510 nm. The reaction is found to conform to the rate law (i). with K₂ and K₃ being the acid dissociation constants of H₃P₂O₈^? and H₂P₂O₈^2?, respectively. The silver(I) catalysis in the reaction has been explained on the basis of complex formation between pdp and silver(I).     

The application of strongly oxidizing agents in flow injection analysis : Part 2. Manganese(III)

The application of manganese(III) as a powerful oxidizing agent in flow injction analysis is described. Manganese(III) is generated electrochemically in the flowing system at a working electrode consisting of a packed bed of gold powder. Spectrophotometric detection is used at 490 nm, where manganese(III) in sulphuric acid solution absorbs strongly. Undr the experimental conditions, the generation of manganese(III) can be accompanied by generation of manganese(IV) and permanganate; manganese(III) alone can be generated by a proper selection of the generating current and the flow rate. Results are presented for the determinatin of various organic and inorganic substances by means of manganese(III), usually at concentrations in the 10^?4—10^? mol l^?1 range. Unlike permanganate and manganese(IV), manganese(III) does not react with chloride, so that oxidizable compounds can be determined in the presence of large amounts of this species.     

Analytical separation of antimony(III) from bismuth(III), lead(II), gallium(III), thallium(III), tellurium(IV) and tin(IV) with cyanex 302

A method is proposed for the separation of antimony(III) (100–400 g) from bismuth(III), lead(II), gallium(III), thallium(III), tellurium(IV) and tin(IV) from an aqueous solution of pH 0.5–1.5 using 8×10^–3–1×10^–2 mol dm^–3 cyanex 302 dissolved in toluene as an extractant. The antimony is stripped from the cyanex phase with water and determined spectrophotometrically with iodide. Various experimental parameters are optimized and the probable 13 stoichiometry of the extracted species is evaluated. The method is applicable to the analysis of alloys and pharmaceutical samples. The separation and determination take only 20 min.     

Simultaneous determination of iron(II), iron(III), and titanium(IV) by flow injection analysis using kinetic spectrophotometry with Tiron

Summary Two flow injection analysis systems have been worked out for the simultaneous determination of Fe(III), Fe(II), and Ti(IV) based on the kinetic spectrophotometry with Tiron. The first system uses a silver reductor column and a single detector with two flow cells aligned in the same optical path to yield two peaks corresponding to (a) Ti(IV)-Tiron and (b) Ti(IV) plus total iron(III)-Tiron complexes. An another sample injection without the silver column yields a single peak which corresponds to Ti(IV) plus Fe(III)-Tiron complexes. With the two sample aliquot injections the system permits simultaneous determinations with throughput of 30 samples/h in the g to several tens g range of each species. The second system is a multidetection system with or without the silver reductor column using the same spectrophotometry with Tiron, in which the entrapment of the sample plug into a closed system allows its repetitive passage through a single detector. With the advantage of much simpler instrumentation, the system permits 6 samples/h to be analyzed for the three metal species with somewhat lower precisions than the first system.     

Metal benzoylpivaloylmethanates. Part III. Manganese(III) and iron(III) chelates

Summary The synthesis and principle properties of several novel tris[1-(4-X-phenyl)-4,4-dimethylpenta-1, 3-dionato]-iron(III) and manganese(III) complexes, where X=MeO, Me, H, F, Cl and NO₂, are described. Magnetic susceptibility measurements in the 4.2–295 K range show a near Curie behaviour and a constant magnetic moment for manganese(III) complexes and for iron complexes, with X=F, Cl or NO₂. Iron complexes with ligands having substituents: X=MeO, Me and H, show weak antiferromagnetic interaction (J=ca.–8 cm^–1 for the two former compounds) and a decrease in magnetic moment with decreasing temperature. In both manganese(III) and iron(III) complexes the diketonate ligand can be easily replaced by chlorine. Equilibrium constants could be evaluated only for substitution of the third diketonate ligand by chloride in the iron complexes on the basis of spectrophotometric measurements. For manganese chelates, the replacement of the second diketonate by chloride is accompanied by reduction of manganese(III) manganese(II) and free organic radical formation is observed.     

Complexes of tetra-tert-butyl-tetraazaporphine with Al(III) and Zr(IV) cations as fluoride selective ionophores

In this work, complexes of Zr(IV) and Al(III) cations with 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraazaporphine (TAP) were tested as ionophores in plasticized PVC membranes of ion-selective electrodes. It was found that both tested ionophores show enhanced affinity towards fluoride anion. High fluoride selectivity was observed in the presence of anionic or cationic additives in the membrane, which indicates that proposed compounds work according to charged or neutral carrier mechanism, depending on membrane composition and pretreatment.tert-Butyl substituents, present in the structure of tested compounds, were supposed to prevent formation of ionophore dimers within the membrane phase. This process was found to be responsible for some unfavorable potentiometric properties of electrodes based on complexes of Zr(IV) and Al(III) cations with porphyrins (compounds closely related to tetra-tert-butyl-5,10,15,20-tetraazaporphine). As it was shown using spectrophotometrical measurements, Al(III)-TAP was not susceptible to dimerization, while dimer formation was observed for Zr(IV)-TAP. In full agreement with these observations, electrodes with membranes containing Al(III)-TAP responded in near-Nernstian and fast manner towards fluoride anion, while the employment of Zr(IV)-TAP as ionophore resulted in super-Nernstian and sluggish response. Plasticized PVC membranes doped with Al(III)-TAP and 20 mol% of lipophilic anionic additives shown remarkable F⁻ selectivity, with selectivity coefficients, , as follows: −4.4 (Y⁻Br⁻), −4.3 (Cl⁻), −4.2 (NO₃⁻), −3.6 (SCN⁻), −2.9 (ClO₄⁻).     

Determination of peroxydiphosphate in acid medium with oxalate (i) with silver(I) as catalyst and (ii) in the presence of excess of manganese(II)

Peroxydiphosphate can be determined with oxalate in acid medium in the presence of silver(I). Excess of oxalic acid along with the sample and silver (I) is heated to boiling and the excess of oxalic acid is titrated against standard permanganate. Another method involves boiling for 2 min a mixture consisting of the sample and excess of manganese(II), followed by titration of the resulting Mn(III) or MnO(2) with standard oxalic acid solution.     

Spectrophotometric determination of cerium(IV), arsenic(III), and nitrite with promazine hydrochloride

Promazine hydrochloride is proposed as a new reagent for the spectrophotometric determination of cerium(IV), arsenic(III), and nitrite. The reagent forms a red-colored radical with cerium(IV) instantaneously in 0.5?2 M sulfuric acid or 0.5?2.5 M phosphoric acid solution. The red radical exhibits maximum absorbance at 505 nm. An 11-fold molar excess of the reagent is necessary for the full development of the color intensity. Beer's law is valid over the concentration range 0.5–15 ppm in sulfuric acid and 0.5–21 ppm in phosphoric acid. The sensitivities of the reaction in sulfuric and phosphoric acid media are 0.022 and 0.019 μg/cm², respectively. The effects of acidity, time, order of addition of reagents, temperature, reagent concentration, and diverse ions are reported. The proposed method offers the advantages of good sensitivity, simplicity, rapidity, selectivity, and a wider range of determination without the need for extraction. Arsenic(III) and nitrite are indirectly determined.     

Study on the interaction of platinum(IV), gold(III) and silver(I) ions with DNA

Fluorescence, absorption spectra have been produced by the interaction of platinum(IV), silver(I) and gold(III) ions with the berberine–DNA system (berberine, Scheme 1). Platinum(IV) and gold(III) ions show different effects from that of silver(I) ion on the spectral characteristics of the berberine–DNA system. Quenching fluorescence is seen with platinum(IV) and gold(III) ions addition, whereas increasing fluorescence is observed for silver(I) ions. The addition of gold(III) and silver(I) ions cause an increase in absorption of the berberine–DNA system. The above results suggest that different metal ions exhibit different affinities when binding to DNA correlates well with the ions’ charge, structure and the coordination ability.     

Kinetics and mechanism of electron transfer reactions in aqueous solutions: Silver(I) catalyzed oxidation of aspartic acid by cerium (IV) in acid perchlorate medium

Silver(I) catalyzed oxidation of aspartic acid by cerium(IV) was studied in acid perchlorate medium. The stoichiometry of the reaction is represented by the eq. (i) Dimeric cerium(IV) species has been indicated and employed in calculations of monomeric cerium(IV) species concentrations. The reaction is second-order and uncatalyzed reaction also simultaneously occurs along with the silver(I) catalyzed reaction conforming to the rate law (ii) where k is an observed second-order rate constant. A probable reaction mechanism is suggested. © 1995 John Wiley & Sons, Inc.