Showing papers in "Journal of Inorganic and Nuclear Chemistry in 1975"

Abstract: The Lewis basicity of oxide (expressed in terms of the optical basicity, Λ) is reduced by highly polarizing cations such as S6+, P5+, Si4+, etc. Λ is shown to be dependent upon the stoichiometry of the medium or compound, the oxidation numbers of the cations and upon a newly defined “basicity moderating” parameter, γ, which is related to the Pauling electronegativity. It is thus possible to calculate ‘theoretical’ optical basicities of various oxyanion media, and these are shown to agree well with experimentally determined optical basicities. It is suggested that such calculations may prove useful in various systems, for example in glasses and in steel-making slags, where u.v. opaqueness prevents experimental measurement of optical basicity. The contrasting solvent properties of various molten salts are explicable in terms of the values of Λ and γ, and the competitive reactions which involve both the Lux-Flood and Lewis acid-base concepts.

Abstract: The hydrolysis behaviour of iron(III) has been investigated in light and heavy water at 25°C and ionic strength 0·10, using ultraviolet spectrophotometry. The equilibrium constant, K11, for the formation of FeOH2+, was found to be 2·90 × 10−3M and 1·41 × 10−3M, respectively, in light and heavy water, providing a value of 0·29 for log ( K 11 H K 11 D ). The formation constant of Fe2(OH)24+, K22, was also investigated and the approximate values of 0·8 × 10−3 M and 0·7 × 10−3 M for H2O and D2O, respectively, were obtained using non-linear least squares analysis. The determination of the formation constant of Fe(OH)2+ was not possible because of the close similarity of the spectrum of this species to that of FeOH2+. The ultraviolet spectra of Feaq.3+, FeOH2+, Fe2(OH)24+, and their deuterium analogues, and Fe(OH)2+, were determined in the 200–360 nm region. The positions of the band maxima were the same in H2O and D2O for each species, but in D2O ϵmax is larger by about 20 per cent and the band width narrower than in H2O. The band maxima occur at the following wave lengths: Feaq3+, 240 nm; FeOH2+, 205 and 297 nm; Fe(OH)2+, 300 nm; Fe2(OH)24+, 240 and 335 nm.

Abstract: The charge-transfer spectra of Ce4+, Pr4+ and Tb4+ in a number of oxides are reported. It is noted that the position of the first charge-transfer band is fixed for the metal ion in an oxygen coordination of VI, but varies in VIII coordination as a function of the host lattice. It is argued that this variation is inherent to the VIII coordination itself.

Abstract: The extraction of alkali cations (Li+, Na+, K+, Rb+, Cs+) by the neutral cyclic polyether dibenzo-18-crown-6 dissolved in various nitrobenzene-toluene mixtures has been studied. Thermodynamic data have been so obtained regarding the alkali cation-cyclic polyether reaction. The affinity of the cyclic polyether for the alkali cations has been found to vary in the order K+ > Rb+ > Cs+ > Na+ > Li+ for all the diluents compositions. Moreover the independence of the selectivity constant, defined as the equilibrium constant of the reaction: Cs + + MSX ⇌ Cs SX + M + (where M is the alkali cation, S the cyclic polyether, X the picrate ion and the bar indicates organic species) on the diluent composition seem to indicate that the complexes formed with the cyclic polyether are isosteric, i.e. with size, shape and external electronic distribution independent of the chemical nature of the cation.

Abstract: Forward and reverse Cs+/H+ and Rb+/H+ ion exchange have been investigated by the batch-procedure in 3rder to obtain both the titration and uptake curves, as well as X-ray diffractograms and water contents of the samples at the various Cs+ or Rb+-loadings. The interlayer distance of the exchanger increases discontinuously with increasing Cs+-loading and three different phases, ZrHCs(PO4)2.2H2O, ZrH0·5Cs1·5(PO4)2.3H2O, and Zr(CsPO4)2.6H2O with interlayer distances of 11·3, 11·7 and 14·2 A, respectively, have been found in the forward process. For the analogous Rb+-ion exchange process the phases were ZrH0·5Rb1·52H2O (10·6 A) and Zr(RbPO4)2.H2O (9·2 A). Reverse ion exchange processes both for Cs+ and Rb+ ions showed a considerable irreversibility especially in the range of 0–50 per cent Cs+ or Rb+-loadings. The replacement of both Cs+ and Rb+ ions by H+ ions occurred together with the formation of solid solutions and therefore the large ion exchange hysteresis loops were ascribed to the formation of different phases in the forward and reverse processes. The X-ray diffraction patterns of the various Rb+ and Cs+-phases dried under different conditions are reported. Finally, a general discussion of the Cs+ or Rb+-ion exchange behavior on zirconium phosphate at various degree of crystallinity is made. It is concluded that the low, apparent selectivity of crystalline zirconium phosphate towards large monovalent ions is due to steric hindrance and therefore enlarged phases of this exchanger, such as Zr(HPO4)2.8H2O (10·4 A), are expected to have a high selectivity towards Cs+ or even larger cations.

Abstract: A chemical procedure is outlined for super-heavy element searches in irradiated uranium targets. The separation scheme is based on the wide range in stability and extractability of chlorometallic complexes by alkyl tertiary and quaternary ammonium chlorides and the wide range of extractability of metal ions by di-2-ethylhexylorthophosphoric acid. These two properties are utilized in various extraction chromatographic systems. The procedure was developed using elements in the sixth period as chemical homologues of super-heavy elements and tested on 100–200 mg irradiated uranium targets. The separation schemes are also applicable to other irradiated targets.

Abstract: The crystal structure and atomic arrangement of uranyl acetate dihydrate, UO2(CH3COO)2·2H2O, have been determined by a single-crystal X-ray diffraction study. The crystal is orthorhombic, space group Pnam, with Z = 4, a = 9·622, b = 14·833, and c = 6·808 A . The structure was solved by Fourier methods and refined to R = 0·041 for 821 observed reflections. The coordination sphere of the uranium contains seven oxygen atoms approximating a pentagonal bipyramid. One-half of the acetate ions link adjacent bipyramids to form chains, while the remaining acetate ions are chelated to individual uranium atoms. Only one of the water molecules is bonded directly to the uranium.

Abstract: The kinetics of the copper(II)/LIX64N system have been studied by a single drop method which highlights the direct dependence of the rate of reaction on interfacial area. The rate of the forward reaction depends on the ratio of the total copper to free proton concentration in the aqueous phase and that of the reverse (stripping) reaction on the product of the copper concentration in the organic phase and the free proton concentration in the aqueous phase. The form of these dependences, however, indicates that a study of the interfacial region is necessary for a detailed understanding of the system.

Abstract: Ion beams of many isotopes of Rb, Cs, Ba, Fr, and Ra have been produced at the ISOLDE facility, CERN, by bombarding heavy element targets with 600 MeV protons, followed by on-line surface ionization and electromagnetic mass separation. Overall production yields are reported, and the prospects for measuring formation cross-sections of short-lived nuclear species are discussed, taking the production of Cs from La as an example. The following half-lives of new nucleides have been determined: 75 Rb (21±3) sec, 76 Rb (36·8±1·5) sec, 116 Cs (3·6±0·2) sec, 136m Cs (19±2) sec, 227 Fr (2·4±0·2) min, 228 Fr (39±1) sec, 229 Fr(50±20) sec, 229Ra (4·0±0·2) min. The systematics of average beta ( β + , EC) strength functions has been updated.

Abstract: The phases formed at elevated temperatures by α-zirconium phosphate (α-ZrP) and its partially exchanged sodium and potassium ion phases have been determined by a combination of thermal and X-ray methods. α-ZrP converts to ζ-ZrP without water loss at 105–115°C. At somewhat higher temperatures one mole of water is lost followed by conversion of ζ-ZrP to ν-ZrP at ca . 230°C. Starting at 400–450° phosphate groups condense by split out of another mole of water. In the process a largely amorphous solid results. This in turn is converted to α-ZrP 2 O 7 at still higher temperatures. Two new partially sodium and potassium exchanged phases were discovered to form at elevated temperatures. The phases have the approximate compositions ZrNa 0·20 H 1·80 (PO 4 ) 2 and ZrNa 0·80 H 1·20 (PO 4 ) 2 and ZrK 0·16 H 1·84 (PO 4 ) 2 and ZrK 0·64 H 1·36 (PO 4 ) 2 in the sodium and potassium ion systems, respectively. The spontaneous disproportionation at room temperature of partially exchanged sodium and potassium ion phases into phases of lower and higher Na + or K + content indicates that ions can diffuse very readily throughout the crystal lattice. In the same context a new phase, λ-ZrP, was prepared by reaction of gaseous HCl with the cation exchanged zirconium phosphate phases.

Abstract: Kinetic measurements were made of three ion-exchange processes—protonation of a carboxylic ion-exchanger, exchange of an anionic complex ion on a strong-base anion-exchanger, and chelation of a metal ion on a chelating ion-exchanger—which are accompanied by fast chemical reactions and are characterized by a sharp moving boundary between the reacted shell and the shrinking unreacted core within each ion-exchanger bead. Analyses of the respective rate data in accordance with a theoretical model showed that all three processes are controlled by the rate of diffusion of the ions penetrating the reacted layer. Diffusion coefficients were determined from the graphical representation of the proposed model.

Abstract: Solutions of 8-hydroxyquinoline in chloroform have been shown to extract the uranyl(VI) ion from aqueous carbonate media and from aqueous solutions of two phenylarsonic acid derivatives, as the species UO 2 (OX) 2 HOX. A method for calculating the overall stability constant, β 3( c ) , of UO 2 (CO 3 ) 3 4− from the resultant distribution date is outlined. The value obtained is log β 3( c ) = 21·54 ± 0·03 at an ionic strength of 0·1 M .

Abstract: Complex solution chemistry associated with formation and growth of hydrous chromium(III) oxide particles of narrow size distribution was investigated. The sols were prepared by heating dilute solutions of chromium(III) salts in the presence of sulfate ions. Upon removal of sol particles by filtration, complex solute species present in the electrolyte medium were separated and characterized using radio-paper electrophoresis. The results indicate that two solute species are involved in solid formation, and that multi-component equilibria are established. The effects of anion concentration and temperature are also discussed.

Abstract: INTRODUCTION ELECTRON SPIN RESONANCE (ESR) study of metalloporphyrins dates back to 1954 when Ingram and Bennett[l] first observed resonances in some derivatives of chlorophyll, hemoglobin and phthalocyanine. Much work has been done since then but no attempt was made to correlate the effect of the type of ligands on the energy levels and the bonding coefficients of the metal ions. All porphyrins may be considered as derivatives of the parent compound, porphine (P) (Fig. la). Naturally occuring porphyrins have substituents only at the pyrrole/3 carbon positions. Substitution at the bridge positions as in tetraphenylporphine (TPP) (Fig. lb), does not take place in nature. Nor does replacement of the bridge methine by nitrogen as in tetrazaporphine flAP) (Fig. lc), fusion of benzene to the pyrrole rings as in tetrabenzoporphine (TBP) (Fig. ld), or both, as in phthalocyanine (Pc) (Fig. le). Difference in substituents at the pyrrole /3 carbon positions have little effect on the spectral properties of metalloporphyrins. Thus, Roberts, Koski and Caughey [2] found that the vanadyl complexes of a few natural porphyfins had identical ESR spectra. On the other hand, spectra of different types of porphyrins as exemplified in Fig. 1 may be expected to differ. The majority of previous work has been concerned with Pc and TPP as ligands. A few studies have used natural porphyrins but none has used TAP or TBP. For metal ions, VO, Cu and Co have been the most studied for the obvious reason of simplicity. The present work is also restricted to these three metal ions but extends the list of ligands to include: (a) TBP, (b) a derivative of TBP, the octamethyltetrabenzoporphine (OMTBP) which was found to be easier to synthesize than TBP[3], and (c) two TPP type porphyrins, the tetra 4-pyridylporphine (TPyP) and the tetra p-carboxyphenylporphine (TCPP). It was hoped that some trend may be detected concerning the effect of the ligands on the energy levels and the bonding parameters of the metal d orbitals. Most metalloporphyrins are approximately square planar[4,5] and, to all intents, the symmetry may be regarded as D4h. However, some metalloporphyrins have out-of-plane metal ions. It is therefore more general to consider the symmetry as C4~ and to drop the usual parity designations. Thus, the d orbitals belong to b,(dx2_~0, a~(dz2), e(dxz, dyz), and b2(d~,). Due to the strong cr overlap between d~,-y, and the ptr atomic orbitals of the pyrrole nitrogens, the b~ molecular orbital (MO) can be expected to be very high in energy but qualitative consideration cannot decide the order of the remaining MO's. Extended Hiickel theory calculations [6] for the first transition series placed at > e > b2 which were nevertheless closely spaced. In the ease of VO, similar calculations [7] yielded the same order but placed al at a considerably higher level, no doubt, due to the strong cr bonding between V and O. ESR results carried out so far has essentially confirmed the above energy order as will be shown later in this paper. Thus, with VO, the single d electron was shown to be in b2, with Cu, the single hole was found in bl and with Co (d7), the odd electron was in a~. The metal d orbital coefficients in the respective MO can be determined from the ESR hyperfine splittings while the coefficients for the excited MO's are usually calculated from the g-tensors. This last calculation is possible only when the excited energies are known. These energies are usually obtained from optical spectra but, unfortunately for metalloporphyrins, the d-d transitions are not observed due to the much stronger ~--Tr transitions. Therefore, in treating the experimental data, one either assumes reasonable values for the energies and calculates the bonding parameters, or vice versa. As an alternative procedure, some authors prefered to calculate only the ratios of the coefficients to the energies. We shall adopt this latter attitude and calculate what we may call the "unreduced" energies, i.e. energies calculated assuming that the coefficient is unity, bearing in mind that they will have to be multiplied by appropriate orbital reduction factors. In comparing a series of similar compounds, this perhaps is good enough practice for detecting trends in certain properties. Since different authors had used different methods in the past, we found it necessary in comparing all results, to take only the experimentally determined parameters of previous work and to recalculate all derived parameters by one and the same method. We have also standardized the notations by assigning the same Greek letters to represent the same orbital coefficients irrespective of which metal ion is being discussed. Thus a, /3, 3' and 8 always refer to the coefficients of dx~-y2, dz:, (dx~, dyz), and dxr respectively regardless of whether we are considering Cu, VO or Co. Solvent effects. A large part of previous work has been carried out with solutions of metalloporphyrins. It is known that solvent molecules have pronounced effects on the ESR of square planar metal complexes by bonding at the axial positions. This is true even for complexes of Cu [8] and VO[9], let alone Co. To isolate the effect due to the solvent from that due to the porphinato ligand itself, it is therefore necessary to compare data of metalloporphyrins which are diluted in the respective free bases or diamagnetic salts. In our work, we have also used solvents but, in this paper, we shall only discuss those results which employed free base dilution and compare them with previous data under similar conditions. The effect of temperature is small if any. (Some authors have claimed identical ESR spectra for room and liquid

Abstract: Tin(IV) chloride derivatives of nickel(II) aldoximates have been obtained by reacting tin(IV) chloride with nickel(II) aldoximates in benzene. All the complexes are coloured solids and appear to be non-electrolytes in DMF. Elemental analyses agree with 1:1 stoichiometry. Magnetic, electronic and far i.r. spectral data suggest that the nickel(II) has changed its configuration from dsp2 square-planar to sp3d2 octahedral one as a result of reaction with the tin(IV) chloride. Tin(IV), also exhibits 6-coordination in these complexes.

Abstract: The products of boiling hydrolysis of ferric chloride solutions have been compared with well-known iron oxide phases by the use of i.r. and Mossbauer spectroscopy, electron microscopy, and chemical reactivity. The product of boiling dilute solutions for a short duration was very similar to the well-known amorphous gel. It appeared to be structurally a mixed phase similar to α-FeOOH and β-FeOOH. Increasing the duration of boiling and the concentration of solutions yielded products which were identified as poorly crystalline α-Fe2O3 and α-FeOOH.

Abstract: Tin(II) alkoxides (Sn(OR)2, R=CH3, C2H5 and C4H9) were synthesized. I.R., H-NMR, mass and Mossbauer spectra are reported and discussed in terms of possible solid and solution state structures. The molecular weight of the butoxy compound is determined in methylene chloride solution and indicates a dimeric substance.

Abstract: Several aliphatic α-hydroxyoximes (H 2 A) not previously characterized are described. The extractability by solutions of these reagents in toluene from 1 M (Na, NH 4 )NO 3 media decreases in the order Fe(III) > Cu(II) > Co(II) ∼ Ni(II). Copper complexes of the types Cu(HA) 2 and CuA are formed, the latter being polymeric in the organic phase. The nickel(II) and iron(III) complexes have the compositions Ni(HA) 2 and Fe(HA) 3 respectively. Extraction of cobalt(II) proceeds irreversibly; cobalt(III) is not extracted. The order of pH values at which different α-hydroxyoximes extract a given metal parallels the expected order of steric hindrance offered by the substituent alkyl groups to the formation of the metal complex.

Abstract: The solvent extraction of zirconium from HCl solutions by dipentyl sulphoxide (DPSO), dioctyl sulphoxide (DOSO), tributyl phosphate (TBP), and their mixtures in various solvents has been studied. At a given H+ strength, the extraction coefficient η of the metal increases with an increase in Cl− activity whereas it is almost independent of H+ at constant Cl−. Under otherwise identical conditions, η increases with an increase in the extractant concentration but is virtually independent of the metal ion concentration over a wide range. The species extracted are ZrCl4·DPSO, ZrCl4·DOSO, and ZrCl4·2TBP. In the case of mixtures, the slope of the log η−log M extractant plot for one component decreases with an increase in the concentration of the second component, the lines crossing at a common point. Extraction is favoured by solvents of low dielectric constant. It is possible to separate zirconium from thorium and uranium by solvent extraction with sulphoxides.

Abstract: The inert cations that accompany the anionic dithiolato complexes, Ni(L)22−(L = S2C2(CN)2, S2C:C(CN)2, S2C:NCN, S2C:C(COOCH3)2, S2C:C(COOC2H5)2, and S2C:N(C6H5) are readily replaced by the coordinately unsaturated M′(P(C6H5)3)2+ (M′ = Ag(I), Cu(I)) complex cations. The i.r. spectra of the crystalline polynuclear complexes Ni(L)2[(P(C6H5)3)nM′]2 (n = 2 or 3) thus obtained indicate that the anion-cation interactions occur primarily through the mercapto groups. In the Ni(S2C:N(C6H5))2[P(C6H5)3)3Cu]2 complex the copper is coordinated to the carbimate nitrogen of the ligand. Interactions of Cu(P(C6H5)3)2+ with the Ni(S2C2(CN)2)2 −2 and Ni(S2C:C(CN)2)22− complexes appear to occur with the π-system of the nitrile groups of the complex ligands. Dinuclear complexes of the composition [M′(P(C6H5)3)2]2L also were obtained and their structures and properties are discussed.

Abstract: The infrared spectra of [M(sal-gly)(H2O)2]2 and[M(sal-gly)]n (M = Co(II) and Ni(II), sal-gly = N-salicylideneglycinate) are discussed. Assignments of characteristic i.r. bands are based on the 15N-labelling of the Ni(II) complexes. Support for assignments of the metal-ligand stretching frequencies (νML) is provided by observing the frequency shifts induced by metal ion substitution. The position of νCO in the dihydrates is indicative of a cis-coordinated octahedral structure in which the metal ion is coordinated to the CO group of the neighbouring ligand.

Abstract: The systems alkalibromide/CoBr2 were investigated by means of difference-thermal-analysis. The compounds CsCoBr3, Cs2CoBr4, Cs3CoBr5; RbCoBr3, Rb2CoBr4; α- and β-K2CoBr4 were found. The system NaBr/CoBr2 is eutectical. LiBr and CoBr2 also form an eutectical system, but with partial miscibility at both sides. The 1:1-compounds cristallize in the CsNiCl3-type, in the 2:1- and 3:1-compounds the Co2+ is tetrahedrally coordinated by Br−.

Abstract: The far i.r. spectra of tetraphenylporphine complexes of Pd(II), Co(II), Cu(II), Ag(II) and Zn(II) have been obtained. In order to aid in the assignment of the metal-nitrogen vibrations the metal isotope technique has been applied to the Ni, Cu, and Zn complexes. Vibrations containing contributions from the metal-nitrogen stretching coordinate have been assigned based on these metal isotope data and the results of a normal coordinate analysis of Zn(II)-porphine. The variation of the frequencies of the major bands is shown to be dependent upon the number of d electrons and is explained on the basis of ligand field stabilization energy.

Abstract: The co-crystallization of the lanthanide(III) and some actinide(III) ethylsulphates was used to study the structures of the f -electron element aquo-ions. To establish the structure of the primary hydration sphere of the Ln 3+ ions use was made of the “reversed” double-double effect (the regularities) in the GdLu range. It was concluded that the coordination number in the Ln(III) aquo-ions decreases from 9 in the LaPm range to 8 for ions from Tb 3+ to Lu 3+ . A similar change is expected to occur in the Bk 3+ -Es 3+ range for the An(III) series.

Abstract: Electron spin resonance and optical solution studies of copper(II) complexes of l -sparteine confirm the rare pseudotetrahedral coordination geometry of copper in solution . Crystal field calculations suggest that only the optical transition near 12·0 kK is due to a “ d − d ” transition. Comparisons to the known optical spectra of Type I copper(II) in metalloenzymes suggest the band near 16·0 kK of Type I copper(II) may be due to a forbidden CuS change transfer band.

Abstract: Zusammenfassung La2Ti2O7 wurde dargestellt und an Einkristallen rontgenographisch untersucht. Gitterkonststanten: a = 25·745, b = 7·810, c = 5·547 A ; Raumgruppe C2v9 − Pna21. Die Kristallstrukturuntersuchung zeigt die Isotypie mit Ca2Nb2O7 und Sr2Nb2O7. Die Ergebnisse werden diskutiert.