Voltammetry of carbocations stabilized by coordination with tetrahedral molybdenum- and tungsten-carbon clusters. [Cp2M2(CO)4-μ-η2:η3-(HCCCR1R2)]+BF4 −(M = Mo,W; R1, R2 = H,Me, and Pri) complexes

The electrochemical reduction of the carbocationic complexes [Cp₂M₂(CO)₄--₂:₃(HCCCR¹R²)]+BF₄ ^–, where M/R¹, R² = Mo/H, H (¹⁺), Mo/H, Me (2 ⁺), Mo/Me, Me (3⁺), Mo/H, Prⁱ (4⁺), has been studied by polarography and cyclic voltammetry on a Hg-electrode in THF solution. It has been suggested that carbocationic center-directed reversible two-electron reduction of1 ⁺–4 ⁺ takes place according to an ECE-mechanism and results in the carbanionic complexes [Cp₂M₂(CO)₄--²:³-(HCCCR¹R²)] (1 ^––4 ^–) as final productsvia carbon-centered radicals as intermediates. Anions1 ^–-4 ^– are capable of irreversible two-electron reduction at more negative potentials or protonation resulting in their transformation into the corresponding acetylene complexes [Cp₂M₂(CO)₄(HCCCHR¹R²)], which are also capable of irreversible two-electron reduction. Anions1 ^––4 ^– and their protonated forms are reduced with cleavage of the Mo-Mo bond. The reduction pathways of complexes1 ⁺,2 ⁺, and4 ⁺ with C-H bonds at the carbon atom of the carbocationic center are different on a Pt-electrode. It is suggested that this difference is due to the abstraction of a H-atom from the intermediate radical species by platinum.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 417–422, March, 1994.     

Cesium dimethyltetrachloroplatinate,a complex of dimethylplatinum(IV). Synthesis and some reductive elimination reactions involving the monomethylplatinum(II) complex as an intermediate

The reduction of Pt(IV) complexes followed by the oxidative addition of dimethyl sulfate to Pt(II) affords Cs₂PtMe₂Cl₄, a complex of dimethylplatinum(IV). On treatment with such nucleophiles as Cl^–, Br^–, I^–, and PtCl₄ ^2– in aqueous solutions at 368 K this complex undergoes reductive elimination to give MeX and Pt^IIMe as a transient species. The latter is further converted to methane upon protolysis, whereas in the presence of an oxidant (Na₂PtCl₆) it gives rise to the Pt^IVMe species. The kinetics of decomposition of Cs₂PtMe₂Cl₄ in aqueous HCl-KCl systems (2M or 3M in Cl^–; [Pt^IVMe₂][Cl^–]) were studied. The reaction takes place as anS _N 2 attack of X^– on the carbon atom of a methyl group located with thetrans position with respect to the aqua-ligand of the [PtMe₂Cl₃(H₂O)]^– complex.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 389–395, February, 1993.     

A study of potassium dicyanoguanidine as a possible analytical reagent

Summary The following ions: Cu⁺⁺, Ag⁺, Hg₂ ⁺⁺, Hg⁺⁺, PtCl₆ ^–-, Pd⁺⁺, Au⁺⁺⁺ in acid solution, produced insoluble compounds with an aqueous solution of potassium dicyanoguanidine. Ferric ion produced a red coloration with the same reagent. The results obtained with PtCl₆ ^–-, Pd⁺⁺ and Fe⁺⁺⁺ are sufficiently characteristic to be used for the detection of these ions.

---

Zusammenfassung Folgende Ionen geben in saurem Milieu mit einer wässerigen Lösung von Kalium-dicyanoguanidin unlösliche Verbindungen: Cu⁺⁺, Ag⁺, Hg₂ ⁺⁺, Hg⁺⁺, PtCl₆ ^–-, Pd⁺⁺ und Au⁺⁺⁺. Ferriionen geben mit demselben Reagens Rotfärbung. Die mit PtCl₆ ^–-, Pd⁺⁺ und Fe⁺⁺⁺ erhaltenen Reaktionsprodukte sind ausreichend charakteristisch, um für den Nachweis dieser Ionen verwendet werden zu können.

---

Résumé Les ions suivants: Cu⁺⁺, Ag⁺, Hg₂ ⁺⁺, Hg⁺⁺, PtCl₆ ^–-, Pd⁺⁺, Au⁺⁺⁺, en solution acide, ont donné des composés insolubles avec une solution aqueuse du dérivé potassé de la dicyanoguanidine. L'ion ferrique a donné une coloration rouge avec le même réactif. Les résultats obtenus avec PtCl₆ ^–-, Pd⁺⁺ et Fe⁺⁺⁺ sont suffisamment caractéristiques pour être employés dans la recherche de ces ions.

---

---

With 2 figures.     

Kinetics of solvolysis and of formation of tetrachloroplatinate(II) in alcohol: Water mixtures

Summary Rate constants are reported for the reaction of [PtCl₄]^2– with hydrochloric-perchloric acid mixtures, in aqueous methanol and aqueous t-butanol at 308.2 K. The observed first-order rate constants are, from their dependence on chloride concentration, divisible into forward and reverse rate constants for the equilibrium: [PtCl₁₄]^2–+H₂O[PtCl₃(OH₂)]^–+Cl^–. The solvent dependence of aquation rates for [PtCl₄]^2– is compared with those for other chlorotransition metal complexes, and discussed in terms of the Grunwald-Winstein method of mechanism diagnosis in organic systems. The solvent dependence of rates of [PtCl₄]^2– formation is compared with the rates of formation of other metal complexes; differences between this platinum reaction and, for example, nickel(II) formation, are rationalised in terms of the reactant charge product difference and consequent solvent permittivity effects on rate trends.     

Effect of ionic interactions on the oxidation of Fe(II) with H2O2 in aqueous solutions

The oxidation of Fe(II) with H₂O₂ has been measured in NaCl and NaClO₄ solutions as a function of pH, temperature T (K) and ionic strength (M, mol-L^–1). The rate constants, k (M^–1-sec^–1), d[Fe(II)]/DT=-k[Fe(II)][₂O₂]at pH=6.5 have been fitted to equations of the formlog k = log k₀+ AI ^1/2+BI+CI ^1/2/T Where log k₀=15.53-3425/T in water; A=–2.3, –1.35; B=0.334, 0.180; and C=391, 235, respectively, for NaCl (=0.09) and NaClO₄ ( =0.08). Measurements made in NaCl solutions with added anions yield rates in the order B(OH) ₄ ^– >HCO ₃ ^– >ClO ₄ ^– >Cl^–>NO ₃ ^– >SO ₄ ^2– and are attributed to the relative strength of the interactions of Fe²⁺ or FeOH⁺ with these anions. The FeB(OH) ₄ ⁺ species is more reactive while the FeCO ₃ ⁰ , FeCl⁺, FeNO ₃ ⁺ and FeSO ₄ ⁰ species are less reactive than the FeOH⁺ ion pair. The general trend is similar to our earlier studies of the oxidation of Fe(II) with O₂ except for B(OH) ₄ ^– . The effect of pH on the logk was found to be a quadratic function of the concentration of H⁺ or OH^– from pH=4 to 8. These results have been attributed to the different rate constants for Fe²⁺ (k₀) and FeOH⁺ (k₁) which are related to the measured k by, k=k_0Fe + k_1FeOH, where _i is the molar fraction of species i. The rates increase due to the greater reactivity of FeOH⁺ compared to Fe²⁺. k₀ is independent of composition and ionic strength but k₁ is a function of ionic strength and composition due to the interactions of FeOH⁺ with various anions.     

Preparation and properties of [PtII(SS)(NN)]-type complexes and their iodine-doped analogues

Summary Complexes of the general formula [Pt(SS) (NN)], where SS is dddt (5,6-dihydro-1,4-dithiin-2,3-dithiolate) or pddt (6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate) and NN is bipy (2,2-bipyridine) or phen (1,10-phenanthroline), were prepared by the reaction of [PtCl₂(NN)] with dithiolate ligands. The¹H-n.m.r. spectra shows upfield shifts in the bipy or phen signals upon substitution of the chlorides in [PtCl₂(bipy)] or [PtCl₂(phen)] by dddt or pddt. The u.v.-vis. spectra exhibits intense intramolecular ligand-to-ligand charge transfer bands ca. 600 nm. Cyclic voltammograms show a reversible oxidation step, assigned to [Pt(SS) (NN)]⁰/[Pt(SS)(NN)]⁺. When the complexes were partially oxidized by I₂, two broad e.s.r. signals atg = 1.91,g = 2.02 appeared. Raman spectra show the presence of I ₃ ^– and I^5/– in the iodine-doped complexes. The electrical conductivities of the neutral mixed ligand complexes (10^–9-10^–10S cm^–1) are raised to 10^–7–10^–8S cm^–1 by I₂ doping.     

Thermodynamics of complexation of lanthanides and some of transition metal ions by 5,5-dimethyl-cyclohexane-2-(2-hydroxyphenyl)-hydrazono-1,3-dione (DCPHD) and its derivatives

Summary Equilibrium betweenDCPHD,DC-4-Cl-PHD, andDC-4-Me-PHD and protons, transition, and lanthanide ions have been investigated at 30 °C by means of potentiometric titration in 75% (v/v) methanol-water mixture containing 0.10M KNO₃ as a constant ionic medium. Thermodynamic parameters (G, H and S) referring to the formation of species HL ^–,L ^––,ML ^+n–2 andML ₂ ^+n–4 (L ^–– denotes the ligand anion) have been determined in solutions. The solvent effects on the thermodynamic parameters of the complex formation are discussed in terms of differences in the donor ability of methanol and water solvents. The plots of thermodynamic parameters versus ionic potential (Z ²/r) of the lanthanide elements is not linear as expected from ionic theory. The obtained curve can be resolved in an initial group (the lighter lanthanides), an intermediate group (Sm-Dy), and a final group (the heavier ones, Tb-Lu). This behavior was explained in terms of differences in the dehydration of lighter lanthanide(III) from that of heavier ones.

---

Thermodynamik der Komplexierung von Lanthaniden und einigen Übergangsmetall-Ionen mit 5,5-Dimethylcyclohexyl-2-(2-hydroxyphenyl)-hydrazono-1,3-dion (DCPHD) und seinen Derivaten

Zusammenfassung Die Gleichgewichte zwischenDCPHD,DC-4-Cl-PHD undDC-4-Me-PHD mit Protonen, Übergangsmetall- und Lanthaniden-Ionen wurden bei 30 °C mittels potentiometrischer Titration in 75% (v/v) Methanol-Wasser mit einem Gehalt an 0.10M KNO₃ als konstantem ionischem Medium untersucht. Die thermodynamischen Parameter G, H und S zur Bildung der Spezies HL ^–,L ^––,ML ^+n–2 undML ₂ ^+n–4 (L ^–– steht für das Ligandenanion) wurden in Lösung bestimmt. Die Lösungsmitteleffekte auf diese Komplexbildungsparameter werden auf Basis der Differenz im Donorvermögen von Methanol und Wasser als Solventien diskutiert. Die Diagramme der thermodynamischen Parameter gegen die ionischen Potentiale (Z ²/r) der Lanthaniden sind, wie nach der Ionentheorie zu erwarten, nicht linear. Die erhaltene Kurve läßt eine Anfangsgruppe (die leichteren Lanthaniden), eine mittlere Gruppe (Sm-Dy) und eine Endgruppe (die schwereren Lanthaniden. Tb-Lu) erkennen. Dieses Verhalten kann aus dem Unterschied im Dehydratationsverhalten erklärt werden.

     

Electrochemical polarization and passivation of iron in acid solutions

Summary The potentiodynamic polarization of the iron electrode in sulphuric acid solutions was studied. The formation of a passivating film on the electrode upon anodic oxidation in sulphuric acid solution depends on the concentration of the acid. Addition of Cl^– ions to sulphuric acid solutions raises the current densities along both the active and passive regions. The difference between the dissolution current in halogen-containing media and solutions devoid of these ions, i. e., the enhancing effect of Cl^– ions, i, varies with the aggressive ions concentration according to log i=a ₅+b ₅ logC _agg. Organic carboxylates enhance the active dissolution of iron through their participation in the dissolution mechanism, while they inhibit pitting corrosion through competitive adsorption with Cl^– ions for adsorption sites on the metal surface.

---

Elektrochemische Polarisation und Passivierung von Eisen in sauren Lösungen

Zusammenfassung Es wurde die potentiodynamische Polarisierung der Eisenelektrode in schwefelsauren Lösungen untersucht. Die Ausbildung eines passivierenden Films auf der Eisenelektrode nach der anodischen Oxidation hängt von der Säurekonzentration ab. Zugabe von Cl^–-Ionen zur Schwefelsäurelösung erhöht die Stromdichten sowohl in den aktiven als auch den passiven Bereichen. Der entsprechende Lösungsstrom mit bzw. ohne diese Ionen, also der verstärkende Effekt der Cl^–-Ionen variiert mit der Konzentration der aggressiven Ionen: log i=a ₅+b ₅ logc _agg. Organische Carboxylate verstärken die aktive Lösung von Eisen durch ihre Teilnahme am Lösungsmechanismus, andererseits inhibieren sie Narben-Korrosion, da sie mit den Cl^–-Ionen bezüglich möglicher Adsorptionsstellen an der Metalloberfläche konkurrieren.

     

Effect of Thallium Ions on Anodic Dissolution of Gold in Alkali–Cyanide Electrolytes at Potentials More Positive Than the NHE Potential

The gold dissolution rate iin solutions containing 0.1 M KOH, 0.1 M KCN, and 2.5 × 10^–7to 1.5 × 10^–5M TlNO₃is studied as a function of potential Eof the electrode whose surface is renewed prior to each experiment, the TlNO₃concentration c, and the time tof the electrode contact with solution. At cexceeding 0.5 × 10^–5M and t 0, the rate is 1.5–2 times that at c= 0. Initial portions of ivs. tcurves in the absence and presence of TlNO₃coincide only at cbelow 10^–6M. Potentiostatic and potentiodynamic measurements show that, at positive E, only small coverages of the electrode surface with thallium are obtained, which make no impact on iat E< 0 and heavily increase it at 0 < E< 0.3 V. The discovered effects are attributed to the formation, during the adsorption of oxidized thallium forms, of dipoles comprising thallium adions and gold atoms. Presumably, the dipoles face the gold with their negative ends and make the potential of zero free charge more negative.     

Crystal Structure of Cesium-Sodium Molybdate Dihydrate

Structure of CsNaMoO₄ · 2H₂O crystals formed in Cs₂MoO₄–Na₂MoO₄–H₂O system is determined by X-ray diffraction study. The unit cell parameters a = 6.379(2) Å, b = 8.631(2) Å, c = 13.670(2) Å, V = 752.6(3) ų, Z = 4, M = 351.87, (calcd) = 3.105 g/cm³, space group P2₁2₁2₁. The isle crystal structure is built of MoO₄ ^2-, Cs⁺, and Na⁺ ions. The Mo–O bond lengths lie within 1.756(2)–1.769(3) Å range. The OMoO bond angle is 109.45° on average. Three oxygen atoms of MoO₄ ^2- anion are involved in hydrogen bonds with water molecules., while the fourth O atom participates in the formation of Na polyhedra only. The octahedral environment of Cs⁺ ions is formed by oxygen atoms of MoO₄ ^2- anions, without participation of water molecules. The structure contains two crystallographically independent water molecules, whose tetrahedral coordination consists of two Na⁺ ions and two MoO₄ ^2- anions.     

Channel inclusion of potassium and tetrachloroplatinate ions in a complex formed between 1,3-diamino-2-propanone and K2PtCl4 in an acidic medium

The crystalline complex dipotassium 1,3-diammonio-2-propanone tetrachloroplatinate trihydrate, formulated as K₂[(NH₃CH₂C)₂O][PtCl₄]₂ · 3H₂O, has been prepared while synthesizing complexes analogous tocis-dichlorodiamine Pt(II). Its structure is orthorhombic, space groupPnma,M _r = 896.1,F(000) = 1640,a = 8.428(4),b = 20.360(10),c = 12.141(7)A,V = 2083.3ų,Z = 4,D _x = 2.860 g cm^–3, (MoK _x) = 196 cm^–1, finalR = 0.083 for 1379 unique reflections. The structure consists of a very extended hydrogen bonded network which involves half of the PtCl₄ ^2– ions, the organic molecules and the water molecules of hydration, leaving large oval channels which accommodate potassium cations and tetrachloroplatinate anions. Within the channel the potassium and tetrachloroplatinate ions pack in columns extending along the a axis. The dense packing is rather reminiscent of that found in the neat salt where each potassium ion is surrounded by six chlorine atoms which describe a polyhedron of a distorted trigonal prism with K⁺ —C1 distances ranging between 3.163–3.187 Å. There is some indirect evidence for the formation of 1,3-diammonio-2-propanone dications which counterbalance the charges of half of the PtCl₄ ^2– ions by protonation of each of the amino nitrogens. The carbonyl oxygens, however, are involved only in a very weak O-C-O interactions along thea axis.     

C–HPt(II) interaction-controlled self-assembly and photophysics of chiral bis(pyrrol-2-ylmethyleneamino)cyclohexane platinum(II) complexes

Reaction of (R,R)-(−)- and (S,S)-(+)-1,2-bis(pyrrol-2-ylmethyleneamino)cyclohexane with K₂PtCl₄ afforded chiral, neutral platinum(II) Schiff base complexes of (R,R)-PtL and (S,S)-PtL with high yields. The rare C–HPt(II) intermolecular interaction was found to show considerable strength and directionality for controlling M and P helical supramolecular architectures of (R,R)-PtL and (S,S)-PtL, respectively, in crystal lattices. More importantly, the open square-planar geometry of platinum(II) complexes allows axial C–HPt(II) interaction, resulting in the ³(ππ^*) excited state with some mixing of the Pt(II) metal character observed both in concentrated solutions and in the solid state at room temperature.     

Über die Definition der Nachweisgrenze

Zusammenfassung Um die Nachweisgrenze zu bewerten, benützt man den Begriff des Entscheidungsniveausy _k , eine Größe, die man mit Hilfe eines zweistufigen Modells bewertet, indem man das Neyman-Pearsonsche Kriterium aus der statistischen Theorie der Signalidentifizierung benutzt. Zu diesem Zweck stellt man eine falsche IdentifizierungswahrscheinlichkeitP ₁₀ fest, so daß , worin den Mittelwert des Blindsignals mit der Standardabweichung _k , und z_k die normierte Abweichung bedeuten, die man aus dem Wert der Laplaceschen Funktion z _k =0,5–P ₁₀ erhält. Das der Nachweisgrenze entsprechende analytische Signal: , worink=z _k –z _i das Verhältnis Signal-Störpegel darstellt und man z_i ebenso aus dem Wert der Laplaceschen Funktion (z _i )=P ₁₁–0,5 erhält (z _i ist negativ). WennP ₁₀=10^–3 undP ₁₁=0,998, erhält mank=6, und die Nachweisgrenze wird: .Die frequentometrisch definierte Nachweisgrenze⁶ hat genau dieselbe Bedeutung, wie jene, die den Begriff des Entscheidungsniveaus bzw. das zweistufige Modell und das Neyman-Pearsonsche Kriterium benutzt.

---

On the definition of the detection limit

Summary In order to estimate the detection limit, the notion of decision levely _k is used, a magnitude which is estimated with the help of a two-stage model, using the Neyman-Pearson criterion from the statistical theory of signals detection. For this reason a fals identification probability P₁₀ is fixed, so that: , where is the mean value of the background fluctuations with the standard deviation _y ,z _k is the normalized deviation obtained from the value of the Laplace function (z _k )=0.5–P ₁₀. The analytical signal corresponding to the detection limit: , wherek=z _k +Z _i , represents the signal-noise ratio andz _i is also obtained from the value of the Laplace function(z_i)=P ₁₁–0.5 (z _i is negative). If one considersP ₁₀=10^–3 andP ₁₁=0.998,k=6 and the detection limit will be: .The detection limit defined frequentometrically⁶ is shown to have just the same significance as that, which uses the notion of decision level or the two-stage model and the Neyman-Pearson criterion respectively.

     

Structural aspects of crown complexes with alkali and alkaline earth cations. Benzo-15-crown-5 as a discriminating macrocycle

X-ray structural results have been reviewed for the related M^z+ L _z ^– -B15C5 complexes where M^z+=Li⁺ to Cs⁺ and Mg²⁺ to Ba²⁺, L^–=2,4,6-trinitrophenolate (Picrate or Pic) and 3,5-dinitrobenzoate (Dnb), and B15C5=benzo-15-crown-5. These results combined with those for come MX_z-B15C5 (X=NCS^–, I^–, NO ₃ ^– , ClO ₄ ^– , BPh ₄ ^– ) complexes have revealed that B15C5 is a useful macrocycle with regard to the within-the-group and between-the-groups discriminations of M^z+ in the solid state.     

Characterization of airborne particulates by laser microprobe mass analysis

Summary Laser microprobe mass analysis (LAMMA) was applied to characterize aerosol particles collected and separated from 16m to 0.06m by a low pressure cascade impactor. Positive ion LAMMA spectra showed characteristic molecular peaks such as PbCl⁺, a series of Si₂O⁺–Si₂O₄ ⁺ and NaAl₂Si₂O₂ ⁺–NaAl₂Si₂O₅ ⁺, and TiO⁺ in 0.06–0.12m, 0.5–1m and 4–8m fraction, respectively. In the negative ion LAMMA spectra, it was observed that the fragment peaks of sulfate ions were deficient above 2m and those of nitrate ions were deficient under 2m. LAMMA allows remarkable insights into the chemical nature of aerosol particles.

---

Charakterisierung luftgetragener Teilchen durch Laser-Microprobe-Massenspektrometrie

Zusammenfassung Laser-Microprobe-Spektrometrie (LAMMS) wurde zur Analyse atmosphärischen Aerosols herangezogen, welches im Korngrößenbereich zwischen 16m und 0.06m mit einem Niederdruckkaskadenimpaktor fraktioniert gesammelt wurde. Positive LAMMS-Spektren zeigten charakteristische molekulare Peaks, wie etwa PbCl⁺, eine Serie von Si₂O⁺–Si₂O₄ ⁺ und NaAl₂Si₂O₂ ⁺–NaAl₂Si₂O₅ ⁺, sowie TiO⁺ in der 0,06–0,12-m,- 0,5–1–m- bzw. 4–8-m-Fraktion. In den negativen LAMMS-Spektren konnten über 2m keine Fragmentpeaks für Sulfationen, unter 2m. keine für Nitrationen beobachtet werden. LAMMS ermöglicht eine bemerkenswerte Einsicht in die chemische Natur von Aerosolteilchen.

     

Synthesis,thermodynamic properties and kinetics of the acid-catalyzed dissociation of nickel(II) diamido polyamino complexes

The ligands 1,10-N,N-bis(2-hydroxymethylbenzoyl)-1,4,7,10-tetraazadecane (L₁) and 1,11-N,N-bis(2-hydroxymethylbenzoyl)-1,4,8,11-tetraazaundecane (L₂) have been synthesized. The stability constants of Ni^II complexes of ligands L₁ and L₂ have been studied at 25 °C using pH titrations. The kinetics of general acid (HCl, 0.04–2.34 mol dm^–3) or buffer (DEPP or DESPEN, 0.05 mol dm^–3, pH 4.83–5.72)-catalyzed dissociation of these Ni^II complexes have been investigated at 25 °C using a stopped-flow spectrophotometer. The ionic strength of solution was controlled at I = 2.34 mol dm^–3 (KCl + HCl) and I = 0.1 mol dm^–3 (KNO₃, buffer), respectively. The kinetic dissociation of Ni^II complexes catalyzed by HCl obeys the equilibrium k _obs = k _1d + k _2H[H⁺], whereas in buffer solution the observed rate constant k _obs = k _d + k _1H[H⁺]. At pH < 1.5, both the proton-assisted and direct protonation pathways contribute to the rates, whereas solvation is the dominant pathway at pH > 6. In the 4.8–5.7 pH range, the complexes dissociate mainly through a proton-assisted pathway.     

Catalytic Activity of Thallium, Lead, and Bismuth Adatoms in the Gold Dissolution Reaction in Cyanide Solutions: A Comparative Characterization

Quartz microgravimetry is used to determine the ratio between coefficients of mass transfer (1 : 0.54 : 0.48), which characterizes relative values of rates of diffusion of hydroxy complexes of thallium, lead, and bismuth in alkaline solutions. The ratio is used when refining the condition under which on a renewable electrode in solutions containing these ions at the concentration c _i the electrode coverage by relevant adatoms _i with increasing duration of contact of the electrode with solution reaches constant values: (c _Tl t) = (0.54c _Pb t) = (0.48c _Bi t). Measured are i,t curves on a renewable gold electrode at E = const in solutions containing 0.1 M KCN, 0.1 M KOH, 0.01 M KAu(CN)₂, and 8 × 10^–6 M compounds of thallium or 1.5 × 10^–5 M, lead, or 1.6 × 10^–5 M, bismuth. Shown is that at (, E) = const the currents of dissolution of gold in these solutions increase in the series Tl < Pb < Bi, which evidences an increase in this series of the catalytic activity of adatoms of these metals. Shown is that at = const the catalytic action of adatoms of thallium and bismuth has an approximately additive character. The obtained data are analyzed with allowance made for the explanation offered earlier for the catalytic effect of adatoms on the anodic dissolution of gold based on the hypothesis about the shift of the potential of the free zero charge in the negative direction after substituting a metal atom for chemisorbed cyanide ions.     

IR study of cation effects on the O-D stretching frequencies of isotopically dilute HDO in aqueous salt solutions

IR spectra of 3 normal solutions of 14 different salts [chlorides of Al⁺⁺⁺, Be⁺⁺, Mg⁺⁺, Ca⁺⁺, Sr⁺⁺, Ba⁺⁺, Zn⁺⁺, Cd⁺⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, N(CH₃) ₄ ⁺ ] in both, 96% H₂O+4% D₂O and 100% H₂O, were measured in the frequency range =2 800–2 100 cm^–1. From up to 18 single measurements for each solution the frequencies and halfwidths of the O-D stretching bands of isotopically dilute HDO were determined with high accuracy. Frequencies in the range =2 510–2 529 cm^–1 and halfwidths in the range =155–205 cm^–1 resulted atT=30°C with standard deviations typical less than ±1 cm^–1 and ±4 cm^–1, respectively. An almost perfect correlation between the O-D stretching band parameters and the polarizing power of the cations was obtained.Herrn Prof. Dr.A. Neckel, Wien, zum 60. Geburtstag gewidmet.     

Determination of the nature of the diperiodatocuprate(III) species in aqueous alkaline medium through a kinetic and mechanistic study on the oxidation of iodide ion

The nature of the diperiodatocuprate(III) (DPC) species present in aqueous alkaline medium has been investigated by a kinetic and mechanistic study on the oxidation of iodide by DPC. The reaction kinetics were studied over the 1.0 × 10^–3–0.1 mol dm^–3 alkali range. The reaction order with respect to DPC, as well as iodide, was found to be unity when [DPC] [I^–]. In the 1.0 × 10^–3–1.0 × 10^–2 mol dm^–3 alkali region, the rate decreased with increase in the alkali concentration and a plot of the pseudo-first order rate constant, k versus 1/[OH^–] was linear. Above 5.0 × 10^–2 mol dm^–3, a plot of k versus [OH^–] was also linear with a non-zero intercept. An increase in ionic strength of the reaction mixtures showed no effect on k at low alkali concentrations, whereas at high concentrations an increase in ionic strength leads to an increase in k. A plot of 1/k versus [periodate] was linear with an intercept in both alkali ranges. Iodine was found to accelerate the reaction at the three different alkali concentrations employed. The observed results indicated the following equilibria for DPC.[Cu(H₂IO₆)₂]^3- [Cu(H₂IO₆)]^- + H₂IO₆ ^3- [Cu(H₂IO₆)] + OH^- [Cu(HIO₆)]^- + H₂OA suitable mechanism has been proposed on the basis of these equilibria to account for the kinetic results.     

Kinetics and mechanism of the acid-catalyzed hydrolysis of [carbonatoethylenediamine(L)2cobalt(III)]+ ions

The kinetics of acid-catalyzed hydrolysis of the [Co(en)(L)₂(O₂CO)]⁺ ion (L = imidazole, 1-methylimidazole, 2-methylimidazole) follows the rate law –d[complex]/dt = {k ₁ K[H⁺]/(1 + K[H⁺])}[complex] (15–30 or 25–40 °C, [H⁺] = 0.1–1.0 M and I = 1.0 M (NaClO₄)). The reaction course consists of a rapid pre-equilibrium protonation, followed by a rate determining chelate ring opening process and subsequent fast release of the one-end bound carbonato ligand. Kinetic parameters, k ₁ and K, at 25 °C are 5.5 × 10^–2 s^–1, 0.44 M^–1 (ImH), 5.1 × 10^–2 s^–1, 0.54 M^–1 (1-Meim) and 3.8 × 10^–3 s^–1, 0.74 M^–1 (2-MeimH) respectively, and activation parameters for k ₁ are H₁ = 43.7 ± 8.9 kJ mol^–1, S₁ = –123 ± 30 J mol^–1 deg^–1 (ImH), H₁ = 43.1 ± 0.3 kJ mol^–1, S₁ = –125 ± 1 J mol^–1 deg^–1 (1-Meim) and H₁ = 64.2 ± 4.3 kJ mol^–1, S₁ = –77 ± 14 J mol^–1 deg^–1 (2-MeimH). The results are compared with those for similar cobalt(III) complexes.