A study on the hydrolytic behavior of thorium (IV) and dioxo-uranium(VI) in the absence and presence of fluoride ions

The hydrolytic behavior of thorium(IV) and dioxo-uranium(VI) was studied in the absence as well as in the presence of small concentration of fluoride in the pH range of 2.0 to 4.0 and 2.0 to 5.5, respectively. Effects of metal ion concentration and time dependence of the hydrolytic process were also investigated. The log values of ₁₁ ^* and ₁₃ ^* computed from the best model of species distribution were found to be -3.51±0.03, and -10.75±0.14 for thorium(IV). Similarly, the best model for dioxo-uranium consisted of ₂₂ ^*, ₄₆ ^* and ₄₇ ^* species having values -6.15±0.05-18.43±0.09 and -23.36±0.07, respectively. Recently developed HYPERQUAD computer program was used for analyzing the various aspects of solution equilibrium species. Different models of chemically possible species distribution were invoked to identify the best model for which HYPERQUAD yields the best fitting of experimental data with least errors. The best model was also decided on the basis of chemical feasibility of the reaction. The species distribution of hydrolytic product remained unaffected in the presence of small quantity of fluoride ions (~1% of thorium and uranium concentration). Moreover, fluoride was found to be helpful in suppressing the early polymerization and colloid formation at the metal ion concentrations investigated. The small amounts of fluoride did not seem to affect the response of glass electrode significantly. The formations of fluoride containing ternary complexes were also not observed at 1% fluoride concentration.     

Crystal structure of the synthetic analog of radtkeite Hg<Subscript>3</Subscript>S<Subscript>2</Subscript>Cl<Subscript>1.00</Subscript>I<Subscript>1.00</Subscript>

The results of structural studies of the synthetic analog of the radtkeite mineral Hg₃S₂Cl_1.00I_1.00 are analyzed. The crystal structure of the compound has been refined; the unit cell parameters are a _m = 16.827(4) , b _m = 9.117(1) , c _m = 13.165(5) , = 130.17(2)°, V = 1543.3(8) ³, space group C2/m, Z = 8, R = 0.0527. A possible transition a ₀ = a _m; b ₀ = a _m + 2c _m; c ₀ = –b _m to the pseudo-orthorhombic F cell previously determined for radtkeite, where one of the angles ( ₀ ) is slightly different from 90° (89.55°), has been found. Each sulfur atom in the structure is bonded to three mercury atoms, forming SHg₃ umbrellas with distances 2.240(6) –2.474(8) and angles HgSHg 94.7(2)°–102.9(2)°. The SHg₃ fragments are linked through Hg vertices to form corrugated [Hg₁₂S₈] layers. The halogen atoms lie inside and between the [Hg₁₂S₈] layers; the distances are Hg-Cl and Hg-I 2.783(7) , 2.961(7) , and 3.083(4) –3.311(3) , respectively.Original Russian Text Copyright © 2004 by N. V. Pervukhina, S. V. Borisov, S. A. Magarill, D. Yu. Naumov, V. I. Vasiliev, and B. G. NenashevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 755–758, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Phase equilibria in the CdI<Subscript>2</Subscript>-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The phase diagram of the system CdI₂-Bi₂O₃ is studied by means of X-ray diffraction, differential thermal analysis and measurements of the density of the material. As a result of the synthetic and peritectic interactions, two incongruently melting intermediate phases i.e. phase A — CdI₂·2Bi₂O₃ and phase B — CdI₂·4Bi₂O₃ (stable in the temperature interval 370–850°C) are formed.The phase A exists in two polymorphic forms with a temperature of the phase transition T =320–370°C. The unit cell parameters at low temperature modification of -CdI₂°2Bi₂O₃ were determined. (a=1.032 nm, b=1.046 nm, c=1.046 nm, =115.02°, =109.11° and =82.04°). The phases A and B have fields of homogeneity.The authors acknowledge thankfully the financial support for this work from the Ministry of Education and Science (Fond Scientific investigations — contract TN-1102).     

Determination of the stability constants of Eu/III/ and Th/IV/ with a heteropolytungstate ion P2W18O 62 6−

Stability constants of Eu/III/ and Th/IV/ with heteropolyanion, P₂W₁₈O ₆₂ ^6– , have been determined by means of the solvent extraction technique. It was found that Eu/III/ forms only 11 complex and Th/IV/ forms 11 and 12 complexes. The stability constants are: Eu/III/: 1g ₁ = 6.71±0.15; Th/IV/: 1g ₁ = 11.3±0.3 and 1g ₂ = 17.8±0.3, at pH 5.00 and the ionic strength of 0.7OM NaCl. The values suggested the complexes would be of inner-sphere type.     

Synthesis,Structure, and Magnetic Properties of the Silicides <Emphasis Type="BoldItalic">RE</Emphasis>IrSi (<Emphasis Type="Italic">RE</Emphasis> = Ce,Pr, Er,Tm, Lu) and SmIr<Subscript>0.266(8)</Subscript>Si<Subscript>1.734(8)</Subscript>

Summary. The equiatomic rare earth metal–iridium–silicides REIrSi (RE=Ce, Pr, Er, Tm, Lu) were prepared by arc-melting of the elements and subsequent annealing. All silicides were characterized through their X-ray powder patterns. The structures of CeIrSi, ErIrSi, and LuIrSi were refined from X-ray single crystal diffractometer data: LaIrSi type, P2₁3, a=629.15(2)pm, wR2=0.1232, 280F² values, and 11 variable parameters for CeIrSi; TiNiSi type, Pnma, a=673.4(1), b=416.07(5), c=744.88(9)pm, wR2=0.0705, 339F² values, and 20 variable parameters for ErIrSi, and a=664.0(3), b=412.9(1), c=742.6(1)pm, wR2=0.0398, 496F² values, and 20 variable parameters for LuIrSi. The iridium and silicon atoms in CeIrSi, ErIrSi, and LuIrSi build three-dimensional [IrSi] networks where the iridium atoms have three (CeIrSi, Ir–Si 229pm) and four (ErIrSi, Ir–Si 247–258pm; LuIrSi, Ir–Si 245–256pm) silicon neighbors. The [IrSi] networks leave larger channels in which the cerium, erbium, and lutetium atoms are located. Temperature dependent susceptibility data for LuIrSi indicate Pauli paramagnetism. CeIrSi shows Curie-Weiss paramagnetism above 100K with an experimental magnetic moment of 2.56(2)_B/Ce atom. With samarium as rare earth metal component the silicide SmIr_0.266(8)Si_1.734(8) with -ThSi₂ type structure was obtained: I4₁/amd, a=409.3(1), c=1397.2(5)pm, wR2=0.0575, 161F² values, and 9 variable parameters. Within the three-dimensional [Ir_0.266Si_1.734] network the Ir/Si–Ir/Si distances range from 230 to 237pm.     

Synthesis and properties of some chromium(III) β-diketonate complexes

Summary Equimolar quantities of CrCl₃ · 3THF and-diketones, -dkH, react to yield CrCl₂(-dk) · 2THF and CrCl₂(-dk) · THF complexes in coordinating and noncoordinating solvents respectively. For 1 : 2 and 1 : 3 molar ratios of reactants, derivatives of general formulae CrCl(-dk)₂ and Cr(-dk)₃ (where-dkH = acerylacetrrnc, benzoylacetonc and dibenzoylmethane) have been isolated. All complexes have been characterized by elemental analysis, molecular weights and by i.r. spectra.     

New derivatives of cyclotriborazane-trimeric B-alkoxy-B-fluoro-N-(β-fluoroethyl)borazenes

The reaction of B-difluoro-N-(-fluoroethyl)borazene with aliphatic alcohols leads to the formation of the previously unknown trimeric B-alkoxy-B-fluoro-N-(-fluoroethyl)borazenes, the corresponding trialkyl borates, and -fluoroethylamine tetrafluoroborate. Four compounds of this type have been synthesized and described, and their IR spectra have been studied. In the presence of anhydrous calcium chloride, the alcoholysis of B-difluoro-N-(-fluoroethyl)borazene leads to the complete decomposition of the molecule with the quantitative formation of calcium fluoride, -chloroethylamine hydrochloride, hydrogen chloride, and a trialkyl borate. The B-alkoxy-B-fluoro-N-(-fluoroethyl)borazenes react with an alcoholic solution of CaCl₂ similarly with the quantitative formation of the corresponding trialkyl borates.     

Inclusion Complexes of Cyclodextrins with Tetrakis(4-carboxyphenyl)porphyrin and Tetrakis(4-sulfonatophenyl)porphyrin in Aqueous Solutions

In neutral and alkaline solutions, tetrakis(4-carboxyphenyl)porphyrin (TCPP) and tetrakis(4-sulfonatophenyl)porphyrin (TSPP) form 1:1 and 2:1 host–guest inclusion complexes with -cyclodextrin (-CD), -cyclodextrin (-CD), and 6-deoxy-6-diethylamino--CD (DEA--CD), except for DEA--CD in alkaline solution. On the other hand, TCPP and TSPP form only 1:1 inclusion complexes with 6-deoxy-6-dihexylamino--CD (DHA--CD). The limited solubilities of DEA--CD in alkaline solution and DHA--CD are likely responsible for no observation of the 2:1 inclusion complex containing DEA--CD in alkaline solution and that containing DHA--CD. The equilibrium constants (Ks) of TCPP and TSPP for the formation of the inclusion complexes have been estimated from the absorption and/or fluorescence intensity changes in neutral and alkaline solutions. The K₂ values, which are the equilibrium constants for the formation of the 2:1 host–guest inclusion complex from the 1:1 inclusion complex, are about one tenth the corresponding K₁ values, except for the -CD–TSPP system in alkaline solution. In neutral solution, where DEA--CD and DHA--CD are in protonated forms, the electrostatic force operates between DEA--CD (DHA--CD) and TCPP (TSPP), leading to the greater K values than those in alkaline solution, where DEA--CD and DHA--CD exist as neutral species.     

Salicylaldehydo chelates of bis(cyclopentadienyl) zirconium(IV)

A new series of organometallic ionic chelates of the type [Cp ₂Zr(sal)]⁺ [ROCS₂/RRNCS₂]^–, where Hsal = salicylaldehyde;R =Me, Et, i-Pr ori-Bu andR =R =Me, Et, i-Pr;R =Me,R = benzyl orR =Et,R =m-tolyl, have been synthesized in aqueous medium by the reaction of [Cp ₂Zr(sal)]⁺Cl^– andROCS ₂ ^– K⁺/RRNCS ₂ ^– Na⁺. These compounds have been characterized by chemical analyses, electrical conductance, electronic, IR and¹H-NMR spectral studies. These studies indicate that the complexes are 1:1 electrolytes and the salicylaldehyde ligand is chelating in all these complexes. Therefore, a tetrahedral coordination about the zirconium atom is proposed.

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Salicylaldehydo-Chelate von Bis(cyclopentadienyl)-zirkonium(IV)

Zusammenfassung Eine neue Gruppe von organometallischen ionischen Chelaten vom Typ [Cp ₂Zr(sal)]⁺ [ROCS₂/RRNCS₂]^– (mit Hsal = Salicyladehyd;R =Me, Et, i-Pr oderi-Bu undR =R =Me, Et, i-Pr;R =Me,R = Benzyl oderR =Et,R =m-Tolyl) wurde in wäßrigem Medium mittels der Reaktion von [Cp ₂Zr(sal)]⁺Cl^– mitROCS ₂ ^– K⁺/RRNCS ₂ ^– Na⁺ hergestellt. Die erhaltenen Verbindungen wurden mittels chemischer Analyse, elektrischer Leitfähigkeit und der IR- sowie¹H-NMR-Spektren charakterisiert. Diese Untersuchungen zeigen, daß die Komplexe 1:1-Elektrolyte sind, wobei der Salicylaldehyd-Ligand in allen Fällen an der Chelatbildung beteiligt ist. Es wird daher für das Zirkoniumatom eine tetrahedrale Koordination vorgeschlagen.

     

<Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR spectra of some drimanic sesquiterpenoids

One- and two-dimensional homo- and heteronuclear correlation proton, carbon, proton—proton, and proton—carbon NMR spectra of fifteen drimanic sesquiterpenoids: 11,12-dibromodrima-5,8-dien-7-one, drim-8-en-7-one, 11-hydroxydrim-8-en-7-one, 11,12-dihydroxydrim-8-en-7-one, 11-hydroxy-11,12-epoxydrim-8-en-7-one, 11-hydroxy-11,12-epoxydrim-8-en-7-one, 8,9-epoxydriman-7-one, 8,9-epoxydriman-7-ol, 11,12-diacetoxydrim-8-en-7-ol, drimane-7,8,11-triol, 7,8-isopropylidenedioxydriman-11-al, 9, 11-dihydroxydrim-7-en-6-one, drimane-7,8,9-triol, drimane-7,8,11-triol, and drim-8-ene-7,11,12-triol were studied. The proton and carbon chemical shifts were assigned.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2589–2594, December, 2004.     

Controlled-potential coulometric studies on fluoride and sulphate complexes of neptunium (VI)

Fluoride and sulphate complexing of Np(VI) has been studied by controlled-potential coulometry at a constant ionic strength. The values of ₁ ^* and ₂ ^* for fluoride complexes were found to be 9.4 and 8.9, respectively, at an ionic strength =0.5. At an ionic strength =1.0, ₁ ^* and ₂ ^* obtained were 6.6 and 10.5, respectively. Sulphate complexing of Np(VI) was studied only at an ionic strength =0.5. The value of ₁ ^* obtained was 5.6.     

Komplexbildung im System Ni2+—o-Methylbenzamidoxim

Zusammenfassung Die Komplexe des Ni²⁺ mit o-Methylbenzamidoxim wurden in neutraler und in alkalischer Lösung spektrophotometrisch untersucht. Die Bildungskonstanten sindK ₁=40 für 11 undK ₂=1,7·10² für 12 in neutraler Lösung und ₁ = =(3,92 ±0,2) · 10⁴für 11 und lgK = lg ₁ + lg ₂ = 3,45 ± ±0,15 für 12 bei 25° und =1 in alkalischer Lösung.

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Complex formation in the systemeNi ²⁺—o-methylbenzamide oxime

The complexes of Ni²⁺ with o-methylbenzamide oxime were investigated spectrophotometrically in neutral as well as in alkaline solution. The formation constants areK ₁=40 for 11 andK ₂=1.7·10² for 12 in the neutral solution and ₁ = =(3.92 ±0.2) · 10⁴ for 11 and lgK = lg ₁ + lg ₂ = 3.45 ± ±0.15 for 12 at 25° and =1 for the alkaline solution. *** DIRECT SUPPORT *** A3615139 00007

     

Preparation and characterization of some stereochemically rigid seven-coordinate η-cyclopentadienyltris(N,N-dialkyldithiocarbamato)hafnium(IV) complexes

Summary N,N-Dialkyldithiocarbametohafnium(IV) complexes of the type -CpHf(S₂CNR₂)₃, (R = Me or Et) have been prepared in nonaqueous media by reacting dichlorodicyclopentadienylhafnium(IV) with sodium salts of substituted dithiocarbamic acids. Conductance and i.r. studies show that these complexes are nonelectrolytes in which all of the dithiocarbamate ligands are bidentate. A coordination number of seven may be assigned to hafnium(IV) in these complexes, 'H n.m.r. spectra of the complexes in CDCI₃ at ambient temperature (30°) indicate that the metal centered rearrangement and the S₂C N bond rotation are both slow on the n.m.r. time scale. A capped octahedron configuration is suggested for these complexes.Author to whore all correspondence should be addressed.     

Complex equilibria of molybdenum(V) and molybdenum(VI) witho-hydroxybenzylamine-N,N,O-triacetic acid (HBATA)

Summary Complex reactions between Mo^V.VI ando-hydroxybenzylamine-N,N,O-triacetic acid (HBATA) have been investigated in the 1–3 and 2.8–6.5 pH range by potentiometric titration at 30° C in 0.5 mol dm^–3 NaCl. The equilibrium data were analyzed with the SCOGS2 and MINIQUAD programs, taking into account side reactions of Mo^V.VI and HBATA with hydrogen ion. The favorable reaction model comprises two complexes, (1,1,1)⁺ and (1,2,2)^–, with formation constants log ₁₁₁ = 14.85 ± 0.11 and log ₁₂₂ = 28.51 ± 0.08 for the Mo^V-HBATA system and the two complexes (1,1,2)^3– and (1,1,3)^2– with formation constants log ₁₁₂ = 17.36 ± 0.01 and log ₁₁₃ = 20.60 ± 0.01 for the Mo^VI-HBATA system. The numbers in brackets refer to the chemical stoichiometric coefficients of molybdenum, HBATA and hydrogen ion in the complexes. The structure and coordinating behaviours of Mo^V and Mo^VI complexes are discussed. The equilibria studied for the polymerization of Mo^V indicates that dimeric, trimeric and tetrameric species are present at pH 1–3.     

Crystal structure of Ba(VUO<Subscript>6</Subscript>)<Subscript>2</Subscript>

The crystal structure of Ba(VUO₆)₂ was determined by X-ray diffraction at 243 K: monoclinic crystal system, space group P2₁/c, unit cell parameters a=6.4992(6) Å, b=8.3803(8) Å, c=10.4235(9) Å, =104.749(2) °, Z=2. The structure contains close-packed [VUO₆] ₂ ^- layers formed by the dimers of the flattened U₂O₁₂ pentagonal bipyramids and by the dimers of V₂O₈ square pyramids. The neighboring layers are bound by the statistically distributed barium atoms.Original Russian Text Copyright © 2004 by E. V. Alekseev, E. V. Suleimanov, E. V. Chuprunov, and G. K. FukinTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 544–548, May–June 2004.     

Comparison of the annealing behavior of thin Ta films deposited onto Si and SiO<Subscript>2</Subscript> substrates

Structural changes at annealing temperatures (T_an) of 500–1,100°C were investigated for thin Ta films which were sputter-deposited onto pure Si substrates and onto thermally oxidized Si. In the as-deposited state, the Ta layers predominantly consist of metastable tetragonal -Ta, whereby the [001] texture is independent of the substrate material. At lower annealing temperatures, the microstructural evolution is essentially the same for both Ta films. Incorporation of O atoms causes an increase of the intrinsic compressive stress, and diffusion of C atoms into the Ta layer leads to the formation of Ta₂C. Additionally, a partial transformation of the original -Ta phase into a second phase with tetragonal unit cell (denoted as -Ta) occurs. For the Ta/Si system, the formation of a Ta–Si intermixing layer is initiated at T_an=550°C, and nucleation of crystalline TaSi₂ occurs at T_an=620°C. The formation of a second Ta silicide was not detected up to T_an=900°C. In the case of the Ta film deposited onto the SiO₂ substrate, the metastable -Ta and the -Ta transform completely into the thermodynamically stable cubic -Ta at T_an=750°C. A marked reaction with the substrate indicated by the formation of Ta₂O₅ and Ta₅Si₃ occurs at T_an=1,000°C.     

Density Functional Theory and Low-Temperature Matrix Investigations of CO-Loss Photochemistry from [(C<Subscript>5</Subscript>R<Subscript>5</Subscript>)Ru(CO)<Subscript>2</Subscript>]<Subscript>2</Subscript> (R = H,Me) Complexes

The photochemical CO-loss products of the diruthenium complexes [CpRu(CO) ₂]₂ (5; Cp = ⁵-C₅H₅), [Cp*Ru(CO)₂]₂ (5*; Cp* = ⁵-C₅(CH₃)₅) and CpCp*[Ru(CO)₂]₂ (5) have been studied experimentally in low-temperature (96 K) matrices in 3-methylpentane by using IR spectroscopy. It is proposed that all three complexes undergo single-CO-loss chemistry but that the products have different structures. The single-CO-loss product from 5 is proposed to have one bridging and two terminal carbonyl ligands, whereas 5* and 5 generate triply bridged CO-loss products similar to that observed from [CpFe(CO)₂]₂ and [Cp*Fe(CO)₂]₂. Double-CO-loss from 5* and 5* 9 is also apparently observed. Relativistic DFT calculations have been carried out on various isomers of the starting materials and on potential CO-loss products from 5. The calculations suggest that the triply bridged product Cp₂Ru₂(-CO)₃ (6) might have a singlet ground state in contrast to the corresponding diiron complex Cp₂Fe₂(-CO)₃ (3), which has a triplet ground state.     

Shear-induced deformation of polystyrene coils in dilute solution from small angle neutron scattering 2. Variation of shear gradient,molecular mass and solvent viscosity

The technique of small angle neutron scattering (SANS) has been used to study the conformation of polystyrene chains in dilute solution under a constant shear gradient. The experiments reveal a distinct anisotropy of the molecular dimensions with regard to the directions parallel and perpendicular to the flow direction on the 2D-multidetector. The deformation ratio of the single polymer chain (R ²/R _iso ² )–1 as a function of the reduced shear gradient=([] · · M _w G)/RT shows a transition from the ideal ²-behaviour for dynamic infinitely flexible coils found at small gradients, to a behaviour with smaller increase at larger. These results are qualitatively consistent with the theory of Cerf for a polymer with finite internal viscosity in a shear gradient. At low(<1), a better agreement with the model of a free-draining coil (Rouse behaviour) than with the Zimm model is observed.     

Neue Molekülverbindungen des β-1,2,3,4,5,6-Hexachlorcyclohexans

Eight new molecular compounds between -1,2,3,4,5,6-hexachlorocyclohexane (-HCH) and some heterocyclic salts (hydrochlorides of - and -picoline, 2,4,6-collidine, ,-bipyridine, isoquinoline, acridine, 9-phenylacridine, and 2,4,6-triphenylpyrylium perchlorate), with the molecular ratio 12, were synthesised and described by means of spectroscopic (IR, UV, NMR) and X-ray-diffraction methods. Some of the molecular compounds may be used for quantitative separation of the heterocyclic salts from complex mixtures.

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Lehrstuhl für Mineralogie.     

A study on the fluoride complexes of plutonium(III), samarium(III) and bismuth(III) using fluoride ion-selective potentiometry

Stability constants of the fluoride complexes of Pu(III), Sm(III) and Bi(III) in 1.0M NaClO₄/HClO₄ medium at 23±1°C have been determined by potentiometry using a fluoride ion-selective electrode. Plutonium was reduced to the trivalent state using quinhydrone with an excess to serve as holding reductant. The log values of concentration stability constants log ₁, log ₂, and log ₃ are 3.58, 6.40 and 12.61 for Pu(III), 3.23, 5.81 and 10.54 for Sm(III) and 3.69, 6.13 and 11.04 for Bi(III), respectively. The log ₂ values in all these cases have very large deviation and may be taken only as rough estimates.