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The thermal dehydration reactions of lanthanoid(III) malonate hydrates Ln2mal3·nH2O (Ln=Ce–Lu; mal=CH2(COO)2; n=6 for Ce–Eu and 8 for Gd–Lu) were investigated mainly by the thermogravimetries under conventional conditions and in atmosphere of water vapor at a constant reduced pressure and a superslow heating rate. The latter conditions were useful especially to detect the formation of new intermediate hydrates, and to determine the dehydration temperatures with accuracy. The main features of the results could be reasonably understood in view of the effects of the lanthanoid contraction.

Five new complexes, [(NH3)5Co(dicarboxylate)Co(NH3)5]X4 (dicarboxylate=oxalate, succinate, pimelate, fumarate, and maleate; X=ClO4− or Cl−), were synthesized by the reactions of [Co(hydrogen dicarboxylate)(NH3)5](ClO4)2 with [Co(NH3)5(H2O)](ClO4)3 and characterized by chromatographic behavior and electronic and NMR techniques. When maleate was used as the dicarboxylate, the formation of [(NH3)5Co(fumarate)Co(NH3)5]4+ as well as [(NH3)5Co(maleate)Co(NH3)5]4+ was observed. The IR and Raman spectra of [(NH3)5Co(oxalate)Co(NH3)5]4+ indicate that the symmetry of the oxalate ion in the complex may be approximated by D2h.

For the measurement of manganese(II)-ion activity, manganese(II) ion-selective electrodes were prepared and tested. As electrodes, heterogeneous membranes were prepared by dispersing sensitive materials, such as manganese sulfide, manganese borate, or manganese dibenzyldithiocarbamate, in silicone rubber, poly(vinyl chloride), or poly(vinyl acetate). A manganese chloride solution (0.1 mol dm−3) was used as the internal reference solution, along with an Ag/AgCl internal reference electrode. The manganese(II) ion-selective electrodes thus made were then examined in terms of their response curves, response times, the effect of the pH, the variation in the response slopes with the temperature, and selectivity coefficients. The response time of the manganese dibenzyldithiocarbamate electrode was within 15 s in the concentration range of 10−8–10−1 mol dm−3. The response slope was 33.14 mV/pMn2+ in the linear part, and the coefficient of correlation was 0.999. The selectivity coefficients were examined by the se...

A rapid method has been established for determination of mixtures of hydrazine and hydroxylamine by potentiometric titration using an iodide ion-selective electrode. Accurate values are obtainable when nitric acid is added to the sample solution. A recommended procedure is proposed in which the sum of hydrazine and hydroxylamine is titrated with an aliquot of sample solution and another aliquot is titrated to the end point for hydrazine after hydroxylamine has been decomposed with nitric acid. Hydrazine and hydroxylamine in mixture can be determined in the concentration range of 0.01–0.5 mmol/dm3. The best result, with relative error and relative standard deviation both of less than 0.7%, may be obtained on 0.5 mmol/dm3 hydrazine and hydroxylamine.

Stoichiometric and kinetic investigations of reactions of the nitric and nitrous acids with hexaaquochromium(II) ions have been carried out in acidic media. The stoichiometries of these reactions found in this work were consistent with the mechanisms proposed by Swaddle,1) in which one mole of nitric acid reacts with four moles of chromium(II) and one mole of nitrous acid reacts with two moles of chromium(II). For the former reaction, it was found that the two-electron reduction of nitric acid by chromium(II) is rate-determining and that the rate constant was 2.2×102 M−1 s−1 at 25 °C and at an ionic strength of 1.0 (NaClO4). For the latter reaction, it was found that the one-electron reduction of nitrous acid by chromium(II) is rate-determining and that the rate constant was 4.5×10−3 M−1 s−1 at 25 °C and at an ionic strength of 1.0 (NaClO4). The rates of the reactions of chromium(II) with anionic species of the parent acids, NO3− and NO2−, were too slow to be detected under the present experimental condit...

Kinetic studies of the reactions of the ferricyanide ion with cobalt(II)-aminopolycarboxylate complexes were carried out. The aminopolycarboxylates used in this study were trimethylenediaminetetraacetate (TRDTA), trans-1,2-cyclohexanediaminetetraacetate (CyDTA), propylenediaminetetraacetate(PDTA), and N-hydroxyethyl ethylenediaminetriacetate(HEDTA). The first step in the reaction is the rapid formation of a binuclear complex intermediate, [(ammopolycarboxylate)CoIIINCFeII(CN)5]n−(n=5 for TRDTA, CyDTA and PDTA and 4 for HEDTA), followed by the dissociation of the intermediate to ferrocyanide and Co(III)-aminopolycarboxylate ions. The equilibrium constant of the formation reaction and the rate constant of the dissociation reaction of the intermediate at an ionic strength of 0.66 were 6.2×102 M−1 and 2.0×10−2 s−1 respectively for the TRDTA system at 5 °C, 3.3×10 M−1 and 2.7×10−2 s−1 for the CyDTA system at 25 °C, and 2.4×103 M−1 and 3.0×10−3 s−1 for the PDTA system at 25 °C. The rate constant of the dissocia...

Theoretical relations were derived for the ECE mechanism involving the reversible deposition of an insoluble species at constant potential (potentiostatic method). Assuming that the activity of deposit becomes equal to unity immediately after the beginning of electrolysis, current-potential relations were obtained for the case in which the first electron transfer step is irreversible and the second one, reversible. The method was used to study the acid hydrolysis of bivalent cobalt complex in the reduction of trans-dibromobis(ethylenediamine)cobalt(III) complex. The measurement made at 5 °C in 0.1 M acetate buffer solutions (pH 4.8) gave 0.4 s−1 for the acid hydrolysis of trans-dibromobis(ethylenediamine)cobalt(II) which was produced by the reduction of cobalt(III) complex.

The d.c. polarographic reduction of Ni(acac)2 and Ni(hfac)2 was studied in detail in dimethyl sulfoxide. Two kinds of tetraalkylammonium perchlorates and sodium perchlorate were used as supporting electrolytes. Ni(acac)2 gave three waves in all the supporting electrolytes, while Ni(hfac)2 gave two waves in the presence of tetraalkylammonium perchlorate. These waves were explained on the basis of the polarographic properties, molecular weights, and conductivities. The electrode reaction mechanism of Ni(acac)2 can be expressed by: (Remark: Graphics omitted.) where the second wave includes a kinetic current. The first wave of Ni(hfac)2 is due to the reduction of Ni(hfac)+ and Ni(hfac)2 themselves; the second wave corresponds to that of free hexafluoroacetylacetonate.

Kinetic studies of the reactions between nitrate ions and Cr(II)–Y complexes, where Y represents cyclohexanediaminetetraacetic acid (CyDTA), trimethylenediaminetetraacetic acid (TRDTA), and N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA), have been carried out. The reaction mechanisms of these complexes at the dropping mercury electrode were found to be expressed by the following equations:(Remark: Graphics omitted.)The formation constant, K, and the rate constants, k1 and k2, were determined in 0.1 M acetate buffer solutions of μ=0.5 by procedures including a curve-fitting method; the results were K=2.0×104 M−1, k1=0.55 M−1 s−1 and k2=2.8 M−1 s−1 for Cr(II)–CyDTA, K=2.4×10−5 M−1, k1=1.0×102 M−1 s−1, and k2

A modified technique for the potentiostatic method has been applied to the study on the outer-sphere association of some substitution-inert complex cations with sulfate ions. The association constants were determined from the change in limiting time as function of the concentration of sulfate ions at ionic strength 0.2 and 25 °C: 29±3 for [Co(NH3)6]3+–SO42−, 23±2 for [Co(en)3]3+–SO42−, 34±3 for [Co(H2O)(NH3)5]3+–SO42−, 18±2 for [Cr(NH3)6]3+–SO42−, 21±2 for [Cr(en)3]3+–SO42−, 19±2 for [Cr(H2O)(NH3)5]3+–SO42−, 13±2 for [Cr(urea)6]3+–SO42−. The ratios of the diffusion coefficient of the univalent ion pairs to that of tervalent substitution-inert complex cations were also obtained. From these ratios, the diffusion coefficients of the univalent ion pairs were calculated; these were found to be close to those of univalent complex ions with similar structures.

The polarographic reduction of hexakis(urea) chromium (III) ions at the dropping mercury electrode has been studied in various supporting electrolyte solutions. This complex exhibits two irreversible reduction waves; the first corresponds to Cr(III)→Cr(II), and the second, to Cr(II)→Cr(0). The kinetic parameters of the electrode reactions were determined in various supporting electrolyte solutions and at varied ionic strengths by means of Tast polarography. The differential-pulse polarographic characteristics of this complex are also given.

A modified instrument for the potentiostatic method (modified pulse polarograph) has been developed, which uses techniques of the time-to-voltage converter. The modified pulse mode and the modified differential pulse mode have been tested as tools for quantitative analysis. The determination of kinetic parameters of electrode reactions is presented, together with the characteristics of the modified pulse polarograph.

The reduction of the cobalt(III) complexes, CoX(NH3)5(3–m)+ (Xm−=Cl−, Br−, NCS−, and H2O) and Co(en)33+, by Cr(II)–HEDTRA was studied by the stopped-flow method, where en and HEDTRA denote ethylenediamine and N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetatic acid respectively. From the kinetic behavior and the spectral properties of the immediate chromium(III) products, it is concluded that the Cr(II)–HEDTRA reductions of CoX(NH3)52+ (X−=Cl−, Br−, and NCS−) are of an inner-sphere type. The effect of the HEDTRA coordinated to chromium(II) on the rates of the electron-transfer reactions is discussed.

In an investigation on the behavior of a cadmium ion-selective electrode in methanol–water and ethanol–water mixtures, potential measurements were carried out with a digital pH/mV meter, a cadmium ion-selective indicator electrode and a silver–silver chloride reference electrode. The calibration curves, slopes of the response, response times, effects of temperature, relation between the potential and the pH-meter reading and selectivity of the electrode were discussed. The response of cadmium ions (electromotive force) was linear between 10−7–10−2 mol dm−3 in water. However, the linear range became narrower with an increase in the alcohol content. The slopes in alcohol–water mixtures (27–33 mV/decade in methanol–water mixtures, 21–29 mV/decade in ethanol–water mixtures) were nearly equal to the Nernstian slope (29.6 mV/decade). The response times of the cadmium ion-selective electrode in 99 v/v% methanol and in 99 v/v% ethanol were somewhat long, but were still within 5 min for all solutions consisting of...

Electrode reactions of mono-, di- and tri-bridged ferrocenophanes ([3]Fcp, [4]Fcp, [3][3]Fcp, [4][3]Fcp, [4][4]Fcp, [3][3][3]Fcp, [4][4][3]Fcp and [4][4][4]Fcp) in acetonitrile were investigated by direct current polarography, pulse polarography, and cyclic voltammetry. The oxidation of these compounds proceeds reversibly as a one-electron process. The linear relationship between the half-wave potential and the number of methylene groups was obtained for ferrocene and ferrocenophanes other than [3][3]Fcp and [3][3][3]Fcp. The Taft substituent constants of trimethylene and tetramethylene groups were estimated.

The thermal dehydration and decomposition of the oxalates of Mg(II), Ca(II), Sr(II), Ba(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) were investigated by means of TG, DTA, DSC, EGA, X-ray powder diffraction analysis, and reflectance and infrared spectroscopies. In general, the temperature at which the oxalates were dehydrated increased with 1/r, where r denotes the radius of metal ion. The heats of dehydration (ΔHH2O) of the alkaline earth metal oxalates increased with 1/r, but those of transition metal oxalates decreased as 1/r increased. By considering the decomposition products, the reactions of anhydrous oxalates were classified into three groups and the relations between the decomposition temperatures and 1/r were discussed for each group.

The chemical equilibria of bis(benzoylacetonato)nickel(II) in dimethyl sulfoxide solutions were investigated, mainly by means of d.c. polarography. In 0.05–0.1 mol dm−3 NaClO4, TMAP, and TBAP solutions, the following chemical equilibria were found: Ni(bi-bzac)2\ightleftharpoonsNi(bi-bzac)(uni-bzac)\ightleftharpoonsNi(bi-bzac)+\ightleftharpoonsNi(uni-bzac)+ where bi- and uni- are the abbreviations of bidentate and unidentate respectively. The species of Ni(bi-bzac)2 and Ni(bi-bzac)(uni-bzac) comprised 35% and 57% respectively of the total complex of 1 mmol dm−3 in a TMAP or TBAP solution, while they accounted for 15% and 77% respectively in a NaClO4 solution. Such a difference in the equilibrium distribution was explained on the basis of the interaction between π electrons of the ligand and cations of the supporting electrolytes. The tris-complex was formed by the addition of excess benzoylacetonate to the complex solution.

The structures of anhydrous dioxalato complexes K2[M(C2O4)2] (M: Mn(II), Co(II), Ni(II), Cu(II), and Zn(II)) prepared by heating their hydrates, were examined by means of infrared absorption and visible reflectance spectroscopy. It was found that the anhydrous complexes of Mn(II), Co(II), and Zn(II) exist in a polynuclear octahedral form with a bridging oxalate group, and those of Ni(II) and Cu(II), in a monomer form. On further heating, the complexes of Be(II), Mn(II), and Zn(II) decomposed into the corresponding metal oxides and potassium oxalate, and those of Co(II), Ni(II), and Cu(II) into the corresponding metals and potassium oxalate. Except for the beryllium(II) complex, the complexes decomposed at lower temperatures with an increase in 1/r, where r is the radius of metal ion.

A kinetic study of the chromium(II) reduction of (O-bonded amino acid)pentaamminecobalt(III) complexes has been carried out in acid solutions. The second-order rate constants in M−1 s−1 (1 M=1 mol dm−3) at 25 °C and I=1.0 M (NaClO4) for α-alanine, phenylalanine, α-aminoisobutyric acid, β-alanine, β-aminobutyric acid, γ-aminobutyric acid, and e-aminohexanoic acid complexes are 1.8×10−2, 1.5×10−2, 2.4×10−3, 7.5×10−2, 5.0×10−2, 1.22×10−1, and 1.49×10−1 respectively. The values of ΔH\eweq lie in the range of 6.4–7.7 kcal mol−1 (1 cal=4.184 J), and those of ΔS\eweq, in the range of −42–−37 cal K−1 mol−1, except for the α-aminoisobutyric acid complex, the ΔH\eweq and ΔS\eweq values of which are 11.4 kcal mol−1 and −32 cal K−1 mol−1 respectively. The role of the amino acid ligands in the inner-sphere electron-transfer reactions is discussed.

Window sweep chronopotentiometry, a new galvanostatic method, has been worked out, the electronic circuit of a window sweep chronopotentiograph and digital simulation of the window sweep chronopotentiogram being presented. Analytical application demonstrating the increase in sensitivity of the galvanostatic method for quantitative analysis is presented.

A polarographic rate study of the acid hydrolysis of [CoX(NH3)5]2+- and trans-[CoX2(N)4]+-type complexes (X=Cl− and Br−; (N)4=(NH3)4, (ethylenediamine)2, (propylenediamine)2 and (1,2-cyclohexanediamine)2) has been carried out in 0.1 M acetate buffer solutions. These complexes gave two polarographic waves; the first wave corresponds to the reduction of Co(III) to Co(II) and the second one, to the reduction of Co(II) to Co(0). The relation between the current and the time of the first wave in a positive potential was dependent on the dissolution wave caused by halogenide ions produced by acid hydrolysis and also on the parallel ECE mechanism. The acid-hydrolysis rate of tervalent cobalt complexes was determined from the variation in the current of the first wave. The rates are: 1.31×10−6 s−1 for [CoCl(NH3)5](NO3)2, 6.25×10−4 s−1 for trans-[CoCl2(NH3)4]ClO4, 3.20×10−5 s−1 for trans-[CoCl2(en)2]NO3, 4.28×10−5 s-1 for trans-[CoCl2(pn)2]ClO4, 1.53×10−4 s−1 for trans-[CoCl2(chxn)2]ClO4·H2O, 5.80×10−6 s−1 for [Co...

The kinetics of the thermal dehydration reactions of MC3H2O4·2H2O(M=Mn(II), Fe(II), Co(II), Ni(II), and Zn(II)) were studied by the Freeman-Carroll and Coats-Redfern methods on the basis of the TG and DTG in nitrogen. The most reasonable reaction order for all the salts was found to be 2/3, indicating that the rate is controlled by the chemical process at a phase-boundary. This was also confirmed by the microscopic observations. The values of activation energy and frequency factor were 70–90 kJ mol−1 and 107–1010 s−1, respectively. The enthalpy changes for all the salts were determined to be 60–80 kJ mol−1 by the DSC measurements. The X-ray powder diffractograms, infrared absorption and diffuse reflectance spectra of the hydrates and anhydrous salts were also examined to obtain informations on their crystal and bonding structures.

A typical reduction wave with a half wave potential of −0.462 V. vs. S. C. E. was obtained with nickel(II) ions in 6 M calcium chloride solution. The a. c. and the Kalousek’s polarograms revealed that the electrode reaction is a quasi-reversible one. From the coulometric measurement carried out at the constant potential, the overall electrode reaction proved to be a two-electron reduction. Nearly the total amount of nickel reduced by the controlled potential electrolysis with the mercury electrode was recovered from the mercury, indicating that the nickel (II) ions are reduced to nickel metal to form probably nickel amalgam. From these experimental results the electrode reaction of nickel (II) ions in 6 M calcium chloride at the mercury electrode was concluded to proceed quasireversibly according to the equationNicl_4^2-+2e+Hg\ightleftarrowsNi(Hg)+4Cl^

The ion association between trioxalatocobaltate(III) anion and uni-, bi- and tervalent cations in aqueous solutions has been studied by polarographic and ultraviolet, visible and infrared spectroscopic methods. The association constants have been obtained by the measurement of the polarographic diffusion current of trioxalatocobaltate(III) ions in the presence of varied concentrations of cations at ionic strength 0.1 (NH4NO3) and 25°C. The influence of ammonium ion was taken into consideration in the treatment of polarographic data. The values obtained are 7.9 for (CH3)4N+[Co(ox)3]3−, 3.7±0.4 for (C2H5)4N+[Co(ox)3]3−, 22±1 for Na+[Co(ox)3]3−, 56±6 for Mg2+[Co-(ox)3]3−, 55±4 for Ca2+[Co(ox)3]3−, 53±3 for Sr2+[Co(ox)3]3−, 55±7 for Ba2+[Co(ox)3]3− and 118±17 for Al3+[Co(ox)3]3−. The association constant of NH4+[Co(ox)3]3− was determined by the conductivity measurement to be 33.6 (logK=1.53) at zero ionic strength. No change was observed in the visible, the ultraviolet and the infrared absorption spectra of t...

The reduction of hexamminechromium(III) ions at the dropping mercury electrode has been studied chronopotentiometrically in acetate buffer solutions. The electrolysis at constant cathodic current gives a well-defined chronopotentiogram which corresponds to the one-electron reduction of chromium(III) to chromium(II), but the anodic chronopotentiogram which is obtained by the electrolysis at constant anodic current is clearly separated from the cathodic one. A general treatment for a chronopotentiometric potential-time curve for the electrode process with the following chemical reaction has been developed by the application of Lagrange’s theorem. The results indicate that hexamminechromium(III) ions are irreversibly reduced at the dropping mercury electrode without any preceding chemical reactions prior to the more or less irreversible electron-transfer process, followed by the rapid aquation of the reduced species.

The rate of the electron-transfer reactions between ethylenediaminetetraacetatochromate(II) and some acidopentaamminechromium(III), CrX(NH3)52+, has been measured at ionic strength 1.0 (NaClO4). The rate constants (l mol−1sec−1) for X=F−, Cl−, Br− and OH− are 2.07 at 25°C, >2×103 at 25°C, 2×103 at 15°C and 2.4×102 at 25°C, respectively. These reactions produce ethylenediaminetetraacetatochromate(III) ions which do not contain an anion X. The mechanisms of these reactions are discussed.

The dissociation reaction of nitrilotriacetatocadmate(II) complexes has been investigated polarographically and chronopotentiometrically in the presence and the absence of acetate ions. The results indicate that the treatment reported by Koryta for the effect of acetate ion on the kinetic current is appropriate. The rate constant of the dissociation reaction of nitrilotriacetatocadmate(II) complexes is a function of hydrogen ion concentration and expressed as k=3.4+2.5×105[H+]+2×108[H+]2 at 25°C.

The formation constants of acetatocadmium-(II) and acetatocobalt(II) complexes were determined at ionic strength of 0.2 at 15, 25 and 35°C with the procedure that is based on the polarographic measurement of the sum of the equilibrium concentrations of the hydrated metal ions and the metal acetate complexes in the substitution reaction involving EDTA complexes. The resulting formation constants KCdOAc and KCoOAc are 27 and 2.1 at 15°C, 16 and 0.6 at 25°C and 20 and 0.6 at 35°C, respectively.

The reduction process of indium(III) at the dropping mercury electrode in thiocyanate solutions has been investigated by direct current polarography, alternating current polaro-graphy and faradaic impedance measurements. The reduction current in the potential region between −0.5 to −0.9 V. vs. saturated calomel electrode is greatly increased by the addition of minute amounts of thiocyanate ions, when a remarkable minimum is observed on the diffusion current plateau at relatively negative potentials. On the alternating current polarogram, indium(III) in a potassium thiocyanate solution gives a negative admittance in the potential region where the minimum appears on the direct current polorogram. The analysis of impedance measurements has shown that the resistance component has a negative value in that potential region. The experimental results have been explained by assuming that the overall electrode process is composed of two simultaneous reactions, one of which proceeds at the naked electrode surface, a...

The reduction of hexamminechromium(III) ion at the dropping mercury electrode has been studied in neutral and acid aqueous solutions. Hexamminechromium(III) ion gives no well-defined d. c. polarographic wave in an unbuffered neutral solution, whereas in an acid solution it gives a well-defined two-step wave, the first wave corresponding to the reduction of chromium(III) to chromium(II) and the second, to that of chromium(II) to chromium-(0).The first wave of the d. c. polarogram obtained in an acid solution is diffusion-controlled and gives a slope of the log-plot close to that expected for a reversible wave. The a. c. and the Kalousek polarogram, however, are of the irreversible type. No chemical reaction involving hydrogen ions, ammonium ions or ammonia takes place preceding the electron transfer. Considering these results, the following mechanism is temporarily suggested for the reduction of hexamminechromium(III) ions at the dropping mercury electrode:[Cr(NH3)6]3++e\ightleftarrows[Cr(NH3)6]2+[Cr(NH3)6...

Kinetics of electron-transfer reactions of ethylenediaminetetraacetatochromate(II) ions with some isothiocyanatoammine complexes of chromium (III), Cr(NCS)n(NH3)6−n(3−n)+(n=0, 1,4 and 6) have been studied. The former ions are present in the forms of both CrII(H2O)edta2− and CrII(H2O)Hedta−, but the reaction of CrII(H2O)Hedta− with Cr(NCS)n(NH3)6−n(3−n)+ is not significant in the pH range from 3.6 to 5.3. Second-order rate constants (l mol−1sec−1) of the reactions between CrII(H2O)edta2− and Cr(NCS)n(NH3)6−n(3−n)+ at ionic strength 1.0 and 25°C are

A new procedure for the determination of the formation constants of metal acetate complexes was developed. The procedure is based on the polarographic measurements of the sum of the equilibrium concentrations of the hydrated metal ions and the metal acetate complexes in the presence of an appropriate auxiliary complex forming substance and of the reference metal ions of which the formation constants of acetate complexes are known.The procedure was applied to the study of acetatocopper(II), acetatolead(II) and acetatozinc(II) complexes, EDTA being used as an auxiliary complex forming substance. The overall formation constants KM(OAc)n (n=1 and 2) for these metal acetate complexes were determined at an ionic strength of 0.2 at 15, 25 and 35°C.

The polarographic method for the determination of the formation constants which is based on the measurement of the effects of acetate and/or other co-existing ions on the equilibrium of the substitution reaction, M+M′L\ightleftarrowsML+M′, has been developed, and applied to the study of the copper(II) complexes with acetate and/or sulfate ions. The formation constants obtained at 25°C and ionic strength 1.0 are: 2·0×10 for KCu(OAc), 1·1×102 for KCu(OAc)2, < 3 for KCuSO4, ∼3×10 for KCu(SO4)2, 4×10 for KCu(OAc)(so4) and ∼7×10 for KCu(OAc)(SO4)2.

Kinetics of the thermal decomposition reactions of [Cr(NH3)6]X3 (X=Br, I and NCS) and [Cr(NCS)(NH3)5](NCS)2 in solid state were studied by the manometric method. The rate constants, activation energies and activation entropies of the substitution reactions of outer-sphere anions for coordinated ammonia molecules were presented, and possible reaction mechanisms were discussed.

The polarographic diffusion current of some tervalent substitution-inert complex cations decreases by the addition of sulfate. From the change in diffusion current the association constants of substitution-inert complex and sulfate ions are obtained at ionic strength 0.1 (NaClO4) and 25°C. The values are 69±8, 58±8 and 4×10 for [Co(NH3)6]3+–SO42−, [Cr(NH3)6]3+–SO42− and [Cr(H2O)6]3+–SO42 respectively. The formation of [Co(NH3)6]3+–HSO4− is negligibly small compared with that of [Co(NH3)6]3+–SO42−.

The SGF MO’s for the π-electron system of 1,10-phenanthroline have been determined by following the Pariser-Parr-Pople’s treatment. For the description of the lower excited states, the configuration interaction among nineteen singly-excited configurations with lower energy has been taken into account. The electronic spectrum of 1,10-phenanthroline has been interpreted on the basis of the results of the theoretical calculation. The SCF MO’s for the π-electron system of a coordinated 1,10-phenanthroline in the tris-iron(II) complex have been determined to be self-consistent under the electrostatic potential field of the central metal ion and the other ligand molecules. On the basis of the results for coordinated ligand, the π-electronic structure of tris-(1,10-phenanthroline)iron(II) ion has been investigated from the theoretical point of view. It has been shown that two kinds of the charge-transfer transitions are responsible for an intense absorption band in the visible region, namely electron transfers f...

A new method for the determination of the formation constants of metal acetate complexes has been developed. The method is based on the polarographic measurement of the sum of the equilibrium concentrations of hydrated metal ions and metal acetate complexes in the presence of an appropriate auxiliary complex-form-ing substance. One of the advantages of the method is that no estimation is required in the course of the calculation. The other is that no information of the dissociation and formation constants is required concerning the auxiliary complex-forming substance.The method is applied to the study of acetatonickel(II) complexes using nitrilo-triacetate as an auxiliary ccmplex-forming substance. The results reveal that only monoacetatonickel (II) ions, NioAc+, exist in the solution containing acetate up to 0.2M in concentration. The formation constants KNiOAc at ionic strength 0.2 are caluclated to be 2.6 at 15°C and 2.4 at 35°C.

Kinetic parameters of the electrode reaction of ethylenediaminetetraacetatoaquochromate-(III)/ethylenediaminetetraacetatoaquochromate(II) at the dropping mercury electrode have been determined by the potentiostatic method in sodium chloride solutions of ionic strength 0.5 containing 0.1 M acetate buffer. The measured standard rate constant (ks)ms is 2.1×10−1cm sec−1 and the measured transfer coefficients (αc)ms and (αa)ms are 0.58 for the cathodic and 0.39 for the anodic process. The correction for the effect of the electrical double layer has been made on these parameters. The values obtained are: (ks)corrc=1.7×10 cm sec−1, (αc)corr=0.54 and (αa)corr=0.43. The standard potential −1.220 V vs. SCE determined by the potentiostatic method is compared with −1.218 V vs. SCE obtained by the measurement of the equilibrium potential. These values are in good agreement within the experimental error.

The complex-forming reaction of nickel (II) with ethylenediaminetetraacetate (EDTA) was found to proceed in acetate buffers of pH 3.8 to 5.2 through four different reaction paths,Ni2++HY3− \xrightarrowk1a NiHY−NiOAc++HY3− \xrightarrowk1b NiHY−+OAc−NiHY− \ightleftarrows NiY2−+H+Ni2++H2Y2− \xrightarrowk2a NiH2YNiOAc++H2Y2− \xrightarrowk2a NiH2Y+OAc−NiH2Y \ightleftarrows NiHY−+H+ \ightleftarrows NiY2−+2H+The change in the polarographic diffusion current of nickel(II) at the rotated dropping mercury electrode was utilized to follow the decrease of the nickel(II) concentration in the reaction mixture after the initiation of the reaction. The rate constants of the reaction paths were determined at 0°C and ionic strength 0.2, with the results:k1a=1.06×104 mol−1 liter sec−1k1b=2.25×104 ”k2a=2.04×102 ”k2b=6.04×102 ”These constants are much smaller than those of the corresponding reactions between copper(II) and EDTA.

The reduction of a series of isothiocyanato-ammine chromium(III) complexes [Cr(NCS)p-(NH3)6−p](3−p)+ at the dropping mercury electrode has been studied. The direct current, the alternating current and the Kalousek polarograms of these complexes have been measured in various supporting electrolyte solutions. The nature of the reduction waves, corresponding to the one-electron reduction of chromium(III) to chromium(II), has been discussed.

The kinetic study of the substitution reaction of copper(II) ions and zinc(II)-nitrilotriacetate complexes in acetate buffer solutions has been carried out with the same procedure as reported previously. The reaction was treated as to proceed through both hydrated metal ions and monoacetato complexes. The rate constants for eight elementary reaction paths, of which four involve the hydrated copper(II) ions and the others the monoacetatocopper(II) complexes, were determined at ionic strength 0.23 at 0°C. The values obtained indicate that all the reactions proceeding through hydrated copper(II) ions are faster than the corresponding reactions proceeding through monoacetatocopper(II) complexes.

The current-potential curves of some substitution-inert complex ions are affected by the change in the composition of the supporting electrolyte. The change in the one-electron reduction wave of hexaquochromium(III) ions with the increase in the concentration of sodium perchlorate and sodium iodide is analyzed in terms of the effect of the structure of the electrical double layer. The addition of sodium sulfate at a constant ionic strength of 0.1 shifts the half-wave potentials of hexaquochromium(III), hexamminechromium(III) and hexamminecobalt(III) ions to more negative potentials. In the case of hexamminecobalt(III), the shift is much greater than in the cases of the former two complex ions. These phenomena are interpreted to be due to the effects of the double layer structure and of the ion association.

The thermodynamic dissociation constants of 2-carboxytropone, 3-carboxytropolone, 4-carboxytropolone, 5-carboxytropolone, 3-carboxy-4-methyltropolone, 3-carboxymethyltropolone, 3,4-dicarboxytropolone and 3-carboxy-4-carboxymethyltropolone have been determined by means of the pH titration with a glass electrode. The relationships between the magnitudes of the dissociation constants and the structures of these compounds have been discussed.

The formation constants of dithiocyanatomercury(II) and tri- and tetrathiocyanatomercurate(II) complexes have been determined by the potentiometric method with a dropping mercury electrode at ionic strength 0.2 and at 15, 25 and 35°C. The values obtained are:at 15°C, KHg(SCN)2c=1.8×1017, KHg(SCN)3c=7.1×1019, KHg(SCN)4c=1.11×1022;at 25°C, KHg(SCN)2c=2.7×1016, KHg(SCN)3c=1.39×1019, KHg(SCN)4c=1.32×1021;at 35°C, KHg(SCN)2c=5.5×1015, KHg(SCN)3c=2.43×1018, KHg(SCN)4c=1.68×1020.The thermodynamic formation constants of these complexes and the free energy change, the enthalpy change and the entropy change of the formation reactions of these complexes have been calculated.

Conformation of trimethylenediaminetetraacetatocobaltate(III) (Cotrdta−) was inferred from the measurement of proton nuclear magnetic resonance spectra. It was found that K[Co-trdta]·2H2O crystals are mixtures consisting of equimolar amounts of the crystals of K[(+)546-Cotrdta]·2H2O and those of K[(−)546Cotrdta]·2H2O; that is, so-called “spontaneous resolution” was found. The absolute configuration of optically active Cotrdta was determined by the measurements of optical rotatory dispersion (ORD) and circular dichroism (CD) curves and by the reaction with ethylenediamine to form tris(ethylenediamine) cobalt(III) cation.

The kinetic study of the substitution reaction of copper(II) ions and cobalt(II)-EDTA complexes in acetate buffer solutions has been carried out with the same procedure as that reported previously. The reaction was found to proceed, under the experimental conditions, through three simultaneous reaction paths similar to those found in the substitution reaction of copper(II) ions and lead(II)-EDTA complexes. The rate constants for three elementary reactions of those reaction paths were determined at ionic strength 0.2 at 5 and 15°C. A reaction path in which the dissociation of cobalt(II)-EDTA complex is rate-determining was not observed in this substitution reaction.

The kinetics of the substitution reaction of nickel(II) and copper(II)-nitrilotriacetate complexes and that of nickel(II) and cobalt(II)-nitrilotriacetate complexes in acetate buffer solutions have been studied by a similar method in principle to that reported previously. The reactions were treated as to proceed through both hydrated metal ions and monoacetato complexes. The rate constants of eight reaction paths, of which four involve hydrated nickel(II) ions and the others, monoacetatonickel(II) complexes, were determined at ionic strength 0.2 at 0°C. The backward reactions were found to proceed also through eight reaction paths in which the dissociation of Ni(II)-nitrilotriacetate complexes is rate-determining. The values of rate constants obtained for the forward and the backward reactions indicate that all the reactions proceeding through monoacetatonickel(II) complexes are faster than the corresponding reactions through hydrated nickel(II) ions.

The systematic synthesis of ammine series of chromium (III) complexes has been developed by using aquopentamminechromium(III) nitrate as a starting material. The procedure for the preparation of aquopentamminechromium(III) nitrate was improved to increase the yield. Twenty five sorts of chromium(III) complexes were obtained by the systematic synthesis, of which the procedures for the preparation of eleven sorts of complexes including a new complex, dinitritotetramminechromium(III) bromide, are described. The visible and ultraviolet absorption spectra in aqueous solutions and infrared spectra in solid state of those complexes have been obtained and their structures are discussed.

The polarogographic behaviors of trans-1,2-cyclohexanediaminetetraacetatochromate(III) complex have been studied. The complex is reduced reversibly at the dropping mercury electrode in the solution which contains 0.4 M sodium chloride, 0.1 M acetate buffer and 2×10−6 M polyoxyethylene lauryl ether. The kinetic parameters of this oxidation-reduction process have been determined from the potentiostatic measurements at 25°C. The measured parameters are: the standard potential (E0)ms=−1.198Vvs. SCE, the standard rate constant (ks)ms=2.9×10−2 cm sec−1, the transfer coefficient for cathodic process (αc)ms=0.33 and that for anodic one (αa)ms=0.67. The Frumkin correction for the electrical double layer has been applied to these parameters and the corrected values thus obtained are: (E0)corr=−1.198Vvs. SCE, (ks)corr=−0.93 cm sec−1, (αc)corr=0.40 and (αa)corr=0.57.