A novel combined electrochemical oscillator from cathode and anode in IO3−/Fe(CN)64− system

Experimental studies have been performed for the simultaneous potential or current oscillations occurring both on cathode and anode in the IO₃⁻/Fe(CN)₆⁴⁻ system. The combined oscillator exhibits very different behavior from that of the individual oscillators on each electrode owing to the different waveforms and incommensurate oscillating frequencies of the individual oscillators. The potential oscillation of the combined oscillator is essentially a sum of those of the individual oscillators for the mixed system, whereas the sum coming from the single systems is slightly different, mainly due to the difference in ionic strength between the single system and the mixed system. The separate current oscillators also seem to interfere with each other, probably through the restricted distribution of the applied voltage in both electrodes and the ohmic drop in addition to the effect of ionic strength.     

The electrochemical Peltier heats of Fe(CN) 6 3− /Fe(CN) 6 4− system at 295.15 K

A specially designed thermo-electrochemical calorimeter was applied to measure the electrochemical Peltier heats (EPH) of Fe(CN) ₆ ^3?/4? system at 295.15 K. The curves of the electrode potential changes and temperature changes against time for Fe(CN) ₆ ^3?/4? couple with five groups of different concentrations were obtained under the condition of various constant-current polarizations. The EPH values for the considered electrode reaction are determined to be ?41.31, ?42.73, ?44.28, ?45.87, and ?46.65 kJ mol^?1 at the respective concentrations of 0.125, 0.175, 0.225, 0.275, and 0.300 mol dm^?3; and the EPH and the apparent enthalpy change corresponding to the infinite dilution to be ?37.42 and ?84.10 kJ mol^?1 at 295.15 K, respectively.     

Separation and preconcentration of131I− and131IO 3 − in a liquid-liquid system

The application of isotope exchange in a liquid-liquid system for the separation and preconcentration of¹³¹I^– and¹³¹IO^3/– from water is described. For this purpose a solution of elemental iodine in tri-n-butyl phosphate diluted with toluene was used. The influence of various factors on the separation efficiency of¹³¹I was investigated. These are: time of the exchange, concentration of a carrier in the aqueous phase, concentration of I₂ in the organic phase, volume ratio of the phases, pH, foreign ions, storage of the organic phase, etc. The method is quite rapid and the selective preconcentration of these chemical forms of radioiodine from water can be accomplished even in the presence of the most important fission products. This method makes also possible to separate these chemical forms from each other under controlled pH conditions. The activity of the separated radioiodine can be measured advantageously, e.g., by homogeneous liquid scintillation counting after decolourization of the organic phase.     

Electronic structure and spectra of [Fe(CN)6SO3]4−

The complex ion [Fe(CN)₆SO₃]⁴⁻ has been prepared in aqueous solution and as the zinc salt in the solid state. The electronic and IR spectra of the complex ion (I) have been recorded. MO calculations have been performed to understand the electronic structure of complex I. The electronic spectra of I and hexacyanoferrate(II) [HCF(II)] have been calculated and compared with the experimental results for I, HCF(II) and HCF(III). The experimental and theoretical results suggest that the oxidation state of Fe in I is + 3 and not +2 and the SO₃ moiety is bonded to one of the nitrogen atoms of the cyano group.     

Interpretation der Absorptionsspektren der Komplexionen [Mo(CN)8]4−, [Mo(CN)8]3−, [W(CN)8]4− und [W(CN)8]3−

Zusammenfassung Die Absorptions- und Reflexionsspektren der Oktocyanokomplexe desMo(IV) undW(IV) sowie die Absorptionsspektren der Oktocyanotomplexe desMo(V) undW(V) werden mitgeteilt. Die Spektren werden unter Zugrundelegung der durch Raman- und IR-spektroskopische Untersuchungen gefordertenD _4d-Symmetrie dieser Verbindungen interpretiert. Die beobachteten Banden niedriger Intensität (log<3) werden Übergängen in einem Termsystem zugeordnet, das für die Konfigurationend ² undd ₁ und die SymmetrieD _4d berechnet worden ist. Banden hoher Intensität (log>3) werden auf Übergänge in antibindende Zustände zurückgeführt, an denen höherep-Zustände des Zentralions sowie Ligandenzustände beteiligt sind. Die erhaltenen Werte des Feldparameters stimmen mit ligandenfeldtheoretischen Erwartungen überein.

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Absorption and reflection spectra of the octacyanides ofMo(IV) andW(IV) and the absorption spectra of the octacyanides ofMo(V) andW(V) are presented. The spectra are interpreted in terms of theD _4d symmetry of the compounds supported by investigations of Raman and infrared spectra. Bands of low intensity (log<3) correspond to transitions between levels obtained in the case of the configurationsd ² andd ¹ respectively, in a field ofD _4d symmetry. Bands of high intensity (log>3) are attributed to transitions into antibonding levels in which p-orbitals of the central ion and ligand orbitals participate. The values of the field parameter obtained are in accord with ligand field theory.

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Résumé Les spectres d'absorption et de réflexion des complexes octocyanurés duMo(IV) et duW(IV) ainsi que les spectres d'absorption des mêmes complexes deMo(V) et de W(V) sont présentés. Les spectres sont interprétés en supposant la symétrieD _4d des molécules indiquée par des analyses des spectres Raman et infrarouges. Les bandes de faible intensité (log<3) sont attribuées à des transitions dans un système de niveaux, calculé pour les configurationsd ² etd ¹, respectivement, en symétrieD _4d. Des bandes de forte intensité (log>3) sont attribuées à des transitions vers des niveaux antiliants auxquels participent des fonctions élevéesp de l'ion central et des fonctions des groupes liés. Les valeurs obtenues pour le paramètre de champ sont en accord avec les prévisions de la théorie.

     

Adsorption of Cl−, Br−, and I− ions from 0.1 M solutions in methanol on Ga, (In-Ga), and (Tl-Ga) electrodes

Adsorption of Cl^?, Br^?, and I^? (Hal^?) ions from 0.1 M solutions in methanol (MeOH) is studied on the liquid renewable Ga, (In-Ga), and (Tl-Ga) electrodes by the methods of differential capacitance and jet electrode. It is shown that the adsorption parameters and the series of surface activity of halide ions in MeOH essentially depend on the metal nature. On the (In-Ga) and (Tl-Ga) electrodes, as well as on the Hg electrode, the surface activity of halide ions increases in the series: Cl^? < Br^? < I^?; on the Ga electrode, it varies in another series: Br^? < Cl^? < I^?. The data for the Ga/MeOH interface support the result, which was first obtained on the Ga/N-methyl formamide (N-MF) interface, that the effect of inversion of surface activity series can be observed not only in the aprotic solvents, but also in the protic solvents. The data, which were obtained in MeOH, are compared with the corresponding data, which were obtained in N-MF, dimethyl formamide (DMF), acetonitrile (AN), and water. For Ga, (In-Ga), and (Tl-Ga) electrodes, the adsorption of Hal^? varies in the series: H₂O < MeOH ≈ N-MF < DMF < AN. The data obtained in MeOH indicate that the energy of metal-Hal^? interaction (ΔG _M-Hal) increases in the series (Tl-Ga) < (In-Ga) < Ga as the electronic work function increases. This is in agreement with the data, which were obtained in other solvents, and is the evidence for the donor-acceptor nature of metal-Hal^? interaction, where the Hal^? ions are the donors of electron pair with respect to the metal.     

Direct versus indirect many-body methods for calculating vertical electron affinities: applications to F−, OH− , NH2−, CN−, Cl−, SH− and PH2−

Electron propagator theory (EPT) is applied to calculating vertical ionization energies of the anions F⁻, Cl⁻, OH⁻,SH⁻, NH₂⁻, PH₂⁻ and CN⁻. Third-order and outer valence approximation (OVA) quasiparticle calculations are compared with ΔMBPT(4) (MBPT, many-body perturbation theory) results using the same basis sets. Agreement with experiment is satisfactory for EPT calculations except for F⁻ and OH⁻, while the ΔMBPT treatments fail for CN⁻. EPT(OVA) estimates are reliable when the discrepancy between second- and third-order results is small. Computational aspects are discussed, showing relative merits of direct and indirect methods for evaluating electron binding energies.     

Raman intensities of liquids: Absolute scattering activities and electro-optical parameters of the halate ions ClO3−, BrO3−, and IO3− in aqueous solutions

Absolute Raman scattering activities of aqueous solutions of sodium bromate and lithium iodate have been measured against NaClO₄ as an external standard. Electro-optical parameters (EOPs) for the BrO and IO bonds were calculated. Equilibrium bond polarizabilities were estimated from refractive index measurements in connection with Raman intensities of the bending modes. Relations between Bragg—Slater radii and EOPs are discussed. EOPS calculated from experimental data are compared with those from ab initio calculations.     

I−/IO3 − Assemblies as Promoters of Iodohydrin Formation

Abstract

The direct conversion of olefins to their corresponding iodohydrins is efficient with I^?/IO₃ ^? assemblies in an aqueous acidic medium. Iodohydrins were obtained in moderately good yields at ambient reaction conditions without employing any metal catalysts. The addition of IOH across the olefin follows the Morkovnikov's rule.     

Bi2(IO3)(IO6): First combination of [IO3]− and [IO6]5− anions in three-dimensional framework

A new bismuth (III) iodate periodate, Bi₂(IO₃)(IO₆) was obtained from hydrothermal reactions using Bi(NO₃)₃·5H₂O, and H₅IO₆ as starting materials. Bi₂(IO₃)(IO₆) crystallizes in the monoclinic space group P2₁/c (No. 14) with lattice parameters ɑ = 8.1119(6), b = 5.4746(4), c = 16.357(1) Å, β = 99.187(2)°, V = 717.07(9) ų, Z = 4. The structure of Bi₂(IO₃)(IO₆) features a three-dimensional framework which is a combination of [Bi(1)O₅] tetragonal pyramids, [Bi(2)O₈] bicapped trigonal prisms and [IO₃]⁻ and [IO₆]⁵⁻ anions. Thermal analysis shows that the compound is thermally stable up to about 350 °C. The solid state UV-vis-NIR diffuse reflectance spectrum indicates that Bi₂(IO₃)(IO₆) is a semiconductor with a band gap of 2.76 eV.     

Structure of the Mo(CN)8 4− ion

Summary The question of the hybridization of the atomic orbitals of Mo in the Mo(CN)₈ ^4– ion is examined, and it is shown that the dodecahedral structure can exist without the participation off electrons.     

Syntheses,structures and properties of two complexes bridged by [M(CN)2] − (M = Ag (I), Au (I))

A dinuclear complex Cu₂(bpca)₂(H₂O)₂(Ag₂(CN)₃) (1) and a 1D complex [Cu₂(bpca)₂(H₂O)₂(Au(CN)₂)₂] _n (2) (bpca = bis(2-pyridylcarbonyl)amide anion) have been prepared, structurally characterized and 2 has been magnetically characterized. The magnetic properties show an antiferromagnetic interaction between the two Cu(II) ions. Based on the Hamiltonian ? = ?2J Σ (S_i · S_{i +1}), best fitting for the experimental data leads to J = ?0.045 cm^?1.     

Infrared spectra and molecular structure of excited electronic metastable states of the nitroprusside anion, [Fe(CN)5NO]2−

Na₂[Fe(CN)₅NO].2H₂O (SNP) and Ba[Fe(CN)₅NO].3H₂O (BNP) irradiated at low temperature with light in the green—blue region exhibit two new sets of infrared (IR) bands. These can be assigned to two, long-lived, electronically excited metastable states of the [Fe(CN)₅NO]²⁻ (NP) ion. Upon heating, these states depopulate following decay processes with different onset temperatures. We considerably extend here previous polarized IR data on irradiated SNP (100) plates to include the other basal planes. All IR-active CN, NO and FeN stretching modes and FENO bending modes of NP in both metastable states exhibit frequency down shifts This points to a softening of the corresponding bonds upon excitation. Relative frequency shift values observed for modes associated with the FeNO group are about one order of magnitude larger than the corresponding values for CN stretching modes. This supports the conclusion that the metastable states are reached through an electronic transition involving mainly the metal(nd)-NO bonding. We employ dichroic measurements in SNP to estimate the orientation in the lattice of the transition dipole moment vector corresponding to the NO mode of NP in both metastable states. Results show that the FeNO group is not appreciably bent upon excitation of NP to either of these states.     

A Study on Thermal Decomposition of K_3[Fe(CN)_6] and KFe[Fe(CN)_6] in Helium

K3 [Fe(CN)6] and KFe[Fe(CN)6] are classical coordination compounds. However, the mechanism of decomposition reactions has not been well expounded. The gas products of thermal decomposition were examined by gas chroma tography (GC) , and the structure of the solid products by Mossbauer spectroscopy(MS) and X-ray diffraction(XRD). The findings are explained in terms of the theory of coordination chemistry and a decomposition mechanism is proposed in this study. On the basis of various experimental results, the first stage of the decomposition of K3[Fe(CN)6] in He was found to be the evolution of(CN)2 resulting in the reduction of Fe(Ⅲ)12K3 [Fe(CN)6]→9K4[Fe(CN)6] + Fe2 [Fe(CN)6] + 6 ( CN )For KFe [Fe(CN) 6 ], the first stage of decomposition man be represented as6KFe[Fe(CN)6]→3K2Fe[Fe(CN)6] + 2Fe2[Fe(CN)6 + 3(CN)2At higher temperatures, the decomposition of both K3[Fe(CN)6) andKFe[Fe(CN)6] to form KCN and Fe2C was accomplished by the release of(CN)2 and N2.     

Small Gold(I) and Gold(I)–Silver(I) Clusters by C−Si Auration

Auration of o-trimethylsilyl arylphosphines leads to the formation of gold and gold–silver clusters with ortho-metalated phosphines displaying 3c–2e Au−C−M bonds (M=Au/Ag). Hexagold clusters [Au₆L₄](X)₂ are obtained by reaction of (L−TMS)AuCl with AgX, whereas reaction with AgX and Ag₂O leads to gold–silver clusters [Au₄Ag₂L₄](X)₂. Oxo-trigold(I) species [Au₃O]⁺ were identified as the intermediates in the formation of the silver-doped clusters. Other [Au₅], [Au₄Ag], and [Au₁₂Ag₄] clusters were also obtained. Clusters containing PAu−Au−AuP structural motif display good catalytic activity in the activation of alkynes under homogeneous conditions.     

Adsorption equilibrium and kinetics of cesium onto insoluble Prussian blue synthesized by an immediate precipitation reaction between Fe3+ and [Fe(CN)6]4−

The adsorption equilibrium and kinetics of cesium ion (Cs⁺) onto insoluble Prussian blue (PB) prepared by an immediate precipitation reaction between Fe³⁺ and [Fe(CN)₆]^4? was investigated under initial Cs⁺ concentration of under 0.15 mmol/L. Synthesis conditions in this method were almost insensitive to the adsorption ability of insoluble PB, and this method provided one of the smallest PB crystallites among synthesis methods. Even when molar concentration of H₃O⁺ was more than 200 times higher or molar concentration of K⁺ was more than 50,000 times higher than that of Cs⁺ in the aqueous solution, the equilibrium adsorption amount was reduced by only approximately one-half to two-third of that in the pure system; that is, the insoluble PB synthesized possessed a considerably high adsorption selectivity for Cs⁺. In contrast to the excellent adsorption ability under adsorption equilibrium, adsorption rate was quite slow. It took at least 2 weeks at 25 °C to completely attain the adsorption equilibrium, even though the primary particle size (crystallite size) and secondary particle size (aggregate size of the crystallites) were sufficiently small at approximately 14 nm and 53–106 μm, respectively. This slow adsorption is primarily due to the large resistance of intracrystalline diffusion; the intracrystalline diffusion coefficient was extremely small at less than 3.3 × 10^?22 m²/s. We also found that increase in temperature could significantly decrease this diffusion resistance, resulting in much quicker elimination of Cs⁺ from the aqueous solution.     

Silver(I)-dithiolate chemistry: Syntheses and characterizations of three new Ag1 cluster anions containingi-MNT [i-MNT= S2CC(CN) in2 su2− ] ligands-[Ag4(i-MNT)4]4−, [Ag8(i-MNT)6(PPh3)4]4−, and [Ag9(i-MNT)6(PPh3)6]3−

The reaction of AgNO₃ with [(“Bu₄N₂ i-MNT)]³ in CH₃CN produces a new silver cluster anion [Ag₄(i-MNT)₄]^4? ,3, a species having a tetrahedral arrangement of silver atoms bridged by fouri-MNT ligands which has been isolated and characterized by X-ray crystallography as [Bu₄N]₂[(PPh₃)₂]₂ [Ag₄(i-MNT)₄],4. The reaction of two or three equivalents of Ag(PPh₃)₂NO₃ with [BzEt₃N]₆[Ag₆(i-MNT)₆] in CH₃CN produces two new clusters, [BzEt₃N]₄[Ag₈(i-MNT)₆(PPh₃)₄],6, and [BzEt₃N]₃[Ag₄(i-MNT)₆(PPh₃)₆], 7, having the common structural feature of an octahedral Ag₆S₁₂ core. The octanuclear Ag₈ cluster also can be synthesized from the reaction of 4 and PPh₃ in CH₂Ck₂ and compound 5 has been structurally characterized as [Bu₄N]₂[(PPh₃)₂N]₂[Ag₈(i-MNT)₆(PPh₃)₄]. The³¹P{¹H} NMR spectrum of 6 in CD₃CN at ?43° shows two sets of two doublets. The corresponding chemical shift and coupling constant of each species is 9.32 ppm (354, 408.8 Hz) and 9.45 ppm (346.7, 401.7 Hz), respectively. Pertinent crystallographic data are as follows: Compound 4 crystallizes in the orthorhombic space group Cc2a, witha=18.668(3)A,b=36.793(4) A,c=17.836(3)A, Z=4, andV= 12250(3)A³. Compound 5 crystallizes in the triclinic space group P1, witha=16.506(3)A,b=17.280(3)A,c=19.144(4) A,x=98.485(14)°, β= 105.44(2)°.y=94.63(2),Z= 1, andV = 5164(2)A³. Compound6 crystallizes in the monoclinic space group C2/m, witha= 25.341(9)A,b= 25.289(9)A,c= 15.076(7)A, β= 107.19(5)°,Z=2, and V=9230(6)A³. Compound7 crystallizes in the monoclinic space group C2/c, witha=25.872(6)A,b=21.288(4) A,c=35,928(5), β=100.98(1)°,Z-4, andV=19426(6)A³.     

Synthesis,crystal structures and magnetic properties of a series of new cyano-bridged complexes derived from templates [Ni(CN)4]2− and [Co(III)(CN)6]3−

Three new cyano-bridged complexes 1 [Ni(tn)₂Ni(CN)₄] (tn?=?1,3-diaminopropane), 2 [Cu^II(dipn)Ni^II(CN)₄], and 3 [Cu(dipn)]₆[Co(CN)₆]₄?·?4H₂O (dipn?=?dipropylenetriamine) have been assembled by the templates [Ni(CN)₄]^2? and [Co(CN)₆]^3?. 1 consists of a one-dimensional linear chain–Ni(tn)₂–NC–Ni(CN)₂–CN–Ni(tn)_2? in which the Ni(II) centers are linked by two CN groups. One 1-D zigzag chain of 2 is formed with–Ni(2)–C–N–Cu(1)–N–C–linkages. A 2D structure of 3 is formed by an alternate array of [Co(CN)₆]^3? and [Co][Cu₆] units. For 1, there is an overall weak antiferromagnetic interaction between Ni(II) ions through the–NC–Ni–CN–bridges of the diamagnetic [Ni(CN)₄]^2? anions. 2 exhibits a weak antiferromagnetic exchange interaction between copper(II) ions mediated by [Ni(CN)₄]^2? diamagnetic bridges. Complex 3 exhibits a weak ferromagnetic interaction between nearest Cu^II and Cu^II atoms through–NC–Co–CN–bridges.