Ab Initio Calculations of Hydroxoplatinum Compounds: II. Binuclear Platinum(IV) Superoxo Complexes

The structural and spectral data have been obtained by ab initio methods for the [(OH)₄Pt(μ-O₂)(μ- OH)Pt(OH)₄]^2?, [(OH)₄Pt(μ-O₂)(μ-OH)Pt(OH)₄(OH)]^3?, [(OH)₅Pt(μ-O₂)Pt(OH)₅]^3?, and [(H₂O)(OH)₄Pt(μ- O₂)Pt(OH)₄(H₂O)]- clusters, corresponding to binuclear platinum(IV) superoxo complexes with one and two bridges. The data obtained are in good agreement with experimental data and make it possible to judge the structure of available complexes.     

Vanadium(V), Cer(IV) und Chrom(VI)

Ohne Zusammenfassung     

Modeling Speciation and Solubility in Aqueous Systems Containing U(IV,VI), Np(IV,V, VI), Pu(III,IV, V,VI), Am(III), and Cm(III)

A comprehensive thermodynamic model, referred to as the Mixed-Solvent Electrolyte model, has been applied to calculate phase equilibria and chemical speciation in selected aqueous actinide systems. The solution chemistry of U(IV, VI), Np(IV, V, VI), Pu(III, IV, V, VI), Am(III), and Cm(III) has been analyzed to develop the parameters of the model. These parameters include the standard-state thermochemical properties of aqueous and solid actinide species as well as the ion interaction parameters that reflect the solution’s nonideality. The model reproduces the solubility behavior and accurately predicts the formation of competing solid phases as a function of pH (from 0 to 14 and higher), temperature (up to 573 K), partial pressure of CO₂ (up to \( p_{{{\text{CO}}_{2} }} \)  = 1 bar), and concentrations of acids (to 127 mol·kg^?1), bases (to 18 mol·kg^?1), carbonates (to 6 mol·kg^?1) and other ionic components (i.e., Na⁺, Ca²⁺, Mg²⁺, OH^?, Cl^?, \( {\text{ClO}}_{4}^{ - } \), and \( {\text{NO}}_{3}^{ - } \)). Redox effects on solubility and speciation have been incorporated into the model, as exemplified by the reductive and oxidative dissolution of Np(VI) and Pu(IV) solids, respectively. Thus, the model can be used to elucidate the phase and chemical equilibria for radionuclides in natural aquatic systems or in nuclear waste repository environments as a function of environmental conditions. Additionally, the model has been applied to systems relevant to nuclear fuel processing, in which nitric acid and nitrate salts of plutonium and uranium are present at high concentrations. The model reproduces speciation and solubility in the U(VI) + HNO₃ + H₂O and Pu(IV, VI) + HNO₃ + H₂O systems up to very high nitric acid concentrations (\( x_{{{\text{HNO}}_{3} }} \approx 0.70 \)). Furthermore, the similarities and differences in the solubility behavior of the actinides have been analyzed in terms of aqueous speciation.     

Zirconium (IV), Thorium (IV) and Dioxouranium (VI) Complexes of Dibasic Tridentate Schiff Bases

Dibasic tridentate Schiff bases obtained by the condensation of O -aminobenzoic acid with salicyldehyde and its 5-chloro and 5-bromo derivatives were synthesised and used to pracipitate Zr(IV), Th(IV) and UO₂(VI) metals as complexes. The 1:1 (metal-ligand) stoichiometry of these complexes is shown by elemental analysis, gravimetric estimations and conductometric titrations while the structures of the complexes are proved by i.r. spectra and thermogravimetric analysis. The magnetic susceptibility measurements by Gouy method show, these complexes to be monormeic and diamagnetic. The molar conductance values in nitrobenzene indicate the nonelectrolytic behaviour of the complexes. The results show that the complexes of the type Zr(OH)²L.H²O, Th(OH)²L.H²O and UO²L.H²O are formed having solvent molecule in co-ordination with metal ion.     

Zirconium (IV), Thorium (IV) and Dioxouranium (VI) Complexes of Dibasic Tridentate Schiff Bases

Dibasic tridentate Schiff bases obtained by the condensation of O -aminobenzoic acid with salicyldehyde and its 5-chloro and 5-bromo derivatives were synthesised and used to pracipitate Zr(IV), Th(IV) and UO₂(VI) metals as complexes. The 1: 1 (metal-ligand) stoichiometry of these complexes is shown by elemental analysis, gravimetric estimations and conductometric titrations while the structures of the complexes are proved by i.r. spectra and thermogravimetric analysis. The magnetic susceptibility measurements by Gouy method show, these complexes to be monormeic and diamagnetic. The molar conductance values in nitrobenzene indicate the nonelectrolytic behaviour of the complexes. The results show that the complexes of the type Zr(OH)₃L.H₂O₂ Th(OH)₂ L.H₂O and UO₂L.H₂O are formed having solvent molecule in co-ordination with metal ion.     

Photoelectron spectra of uranium(IV), (V) and (VI) complexes

Satellites were observed on 4f photoelectron spectra of uranium (IV) complexes, while none was seen for diamagnetic uranyl complexes. Photoelectron lines of oxygen 1s coordinated to the uranium ion were broad for NaUO₃ and uranyl complexes.     

Investigation of removal of Cr(VI), Mo(VI), W(VI), V(IV), and V(V) oxy-ions from industrial waste-waters by adsorption and electrosorption at high-area carbon cloth

Adsorption and electrosorption of Cr(VI), Mo(VI), W(VI), V(IV), and V(V) ions from water samples at low concentration were studied at high-area C-cloth electrodes. The concentrations of ions in the solution were monitored using in situ UV spectroscopy. All the investigated ions, except V(IV), showed better adsorption in acidic media. Positive polarization of the C-cloth caused increased adsorption of Cr(VI), Mo(VI), and V(V) ions. When previously adsorbed, Mo(VI) and V(V) ions were shown to be largely desorbable by negative polarization of the C-cloth. Since V(IV) does not become adsorbed significantly at the C-cloth in acidic media, the method provides an interesting means for separation of V(V) and V(IV) species in solution.     

Molybdenum(VI), (V) and (IV) complexes with chiral benzoin thiosemicarbazone

The chiral (ONS) dianionic Schiff base ligand benzoin thiosemicarbazone (H₂L) reacts with MoO₂(acac)₂ to give the polymeric complex [(MoO₂L) _n ] (1) (Type 1). The reaction of MoO₂L with pyridine (py), 3-picoline (3-pic) or 4-picoline (4-pic) gives [Mo^VIO₂LD] (D = py, 3-pic or 4-pic) (Type 1). Further, the reaction of [MoO₂L] or [MoO₂LD] with PPh₃ or reaction of [MoO₂L] with PPh₃ (plus bpy or phen, D) in the presence of donor reagents D gives [Mo^IVOL] or [Mo^IVOLD] (Type 2). On the other hand, the reaction of [MoO₂L] with hydrazides (zdhH₃) such as benzoylhydrazine (bhH₃), isonicotinoylhydrazine (inhH₃), nicotinoylhydrazine (nhH₃), salicyloylhydrazine (slhH₃) and thiosemicarbazide (tscH₃) produced non-oxo–diazenido complexes [MoL(zdh)] (Type 3). The complexes have been characterized by elemental analyses, molar conductance, magnetic moment, electronic, i.r. and e.s.r. spectroscopic measurements.     

Pentacoordinate NiII Complexes: Preparation,Magnetic Measurements,and Ab Initio Calculations of the Magnetic Anisotropy Terms

Two novel mononuclear five‐coordinate nickel complexes with distorted square‐pyramidal geometries are presented. They result from association of a tridentate “half‐unit” ligand and 6,6′‐dimethyl‐2,2′‐bipyridine according to a stepwise process that highlights the advantage of coordination chemistry in isolating an unstable tridentate ligand by nickel chelation. Their zero‐field splittings (ZFS) were studied by means of magnetic data and state‐of‐the‐art ab initio calculations. Good agreement between the experimental and theoretical axial D parameters confirms that large single‐ion nickel anisotropies are accessible. The synthetic process can also yield dinuclear nickel complexes in which the nickel ions are hexacoordinate. This possibility is facilitated by the presence of phenoxo oxygen atoms in the tridentate ligand that can introduce a bridge between the two nickel ions. Two different double bridges are characterized, with the bridging oxygen atoms coming from each nickel ion or from the same nickel ion. This coordination change introduces a difference in the antiferromagnetic interaction parameter J. Although the magnetic data confirm the presence of single‐ion anisotropies in these complexes, these terms cannot be determined in a straightforward way from experiment due to the mismatch between the principal axes of the local anisotropies and the presence of intersite anisotropies.     

HcnS^—与HSC^—n簇离子的量子化学从头计算

应用量子化学从头计算能量解析梯度法，以ＨＦ６／３１Ｇ为基组优化了ＨＣｎＳ＾－与ＨＳＣ＾－ｎ（ｎ＝１～９）同分异构团簇离子的几何结构，计算了它们的电子总能量，结果显示ＨＣｎＳ＾－比相应的ＨＳＣ＾－ｎ稳定，从相邻簇离子的能量差及簇离子的平均原子结构能可知ｎ为偶数的ＨＣｎＳ＾－与ＨＳＣｎ＾－较ｎ为奇数的簇离子稳定，能量的差异随着ｎ的增加而逐渐减小，计算和实验结果完全相符，还分别计算了ＨＣｎＳ＾－失去Ｈ，     

Acetylenic β-keto Ester of Th(IV), U(IV), and U(VI) Compounds

Acetylenic β-keto ester (L) compounds ML₄ (M = Th and U), and UO₂L₂ · EtOH have been prepared by reactions in non-aqueous solvents. The infrared spectra of these compounds are reported together with some of their chemical properties.     

Die quantitative Oxydation von Methanol (I), ?thyl- (II), Propyl- (III), Isopropyl (IV), Butyl- (V) und Isobutylalkohol (VI)

Ohne Zusammenfassung     

Mechanistic Photodissociation of Glycolaldehyde: Insights from Ab Initio and RRKM Calculations

Herein we report a theoretical study on mechanistic photodissociation of glycolaldehyde, HOCH₂CHO. Equilibrium structures, transition states, and intersection structures for the α‐C? C and ‐C? H bond fissions and the β‐C? O bond fission in the excited states are determined by the complete active space self‐consistent field (CASSCF) method. Based on the CASSCF optimized structures, the potential energy profiles for the dissociations are refined by performing single‐point calculations using the multi‐state multi‐reference CASSCF second order perturbation (MS‐MR‐CASPT2) method. With a low excitation energy of 280–340 nm, the T₁ α‐C? C and β‐C? O bond fissions following intersystem crossing from the S₁ state are the predominant and comparable channels, whereas the α‐C? H bond fissions both in the S₁ and in the T₁ states are nearly prohibited due to the relevant high barriers. The rate constants for the T₁ α‐C? C and β‐C? O bond fissions are also calculated by RRKM theory. Furthermore, the S₀ reactions can occur as a consequence of intersystem crossing via T₁/S₀ intersection points resulting from the T₁ C? C and C? O bond cleavages. This photodissociation mechanism is consistent with recent experimental studies.     

Tungsten(VI) and Tungsten(V) Fluoride Complexes

WF₆ reacts with phosphines R₃P forming 1:1 compounds. With R=P(CH₃)₃ the coordination around the tungsten atom is capped trigonal prismatic, with R=P(CH₃)₂C₆H₅ the coordination is capped octahedral, as established by single‐crystal structure determinations: [(CH₃)₃P? WF₆]: a=752.5(21), b=945.7(24), c=629.8(18) pm. β=110.36(13)°, space group Cm, Z=2; [(CH₃)₂(C₆H₅)P? WF₆]: a=762.2(2), b=1123.5(2), c=2647.5(6) pm, space group Pbca, Z=8. [(CF₃CH₂)₂N? WF₅] reacts smoothly with P(C₆H₅)₃ forming known P(C₆H₅)₃(F)₂ and [(CF₃CH₂)₂N? WF₄? P(C₆H₅)₃], a stable, green, molecular species, identified among other methods with an crystal structure determination: a=914.9(1), b=956.0(1), c=1449.8(2) pm, α=7.642(4), β=81.648(3), γ=81.519°, space group P$\bar 1$ , Z=2.     

Thin-layer chromatographic separation of Se(IV), Te(IV), V(V), and Mo(VI) as ternary mixtures and their identification with potassium thiocarbonate (PTC) reagent

Summary Thin-layer chromatography of Se(IV), Te(IV), V(V), and Mo(VI) as ternary mixtures has been described. The separation was effected on a silica gel G layer by employing two different solvent systems: diethyl oxalate-HCl (601v/v) andn-butyl acetate-HCl (400.6v/v). The chromatograms were visualized with 0.1M potassium thiocarbonate (PTC) spray and the limits of identification as determined, lie between 1.27 and 2.04g.

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Zusammenfassung Die Dünnschichtchromatographie ternärer Gemische von Se(IV), Te(IV), V(V) und Mo(VI) wurde beschrieben. Die Trennung wurde auf Schichten von Kieselgel G mit zwei verschiedenen Lösungsmittelsystemen durchgeführt: Diäthyloxalat—Salzsäure (601) und n-Butylacetat—Salzsäure (400,6). Die Chromatogramme wurden mit 0,1-m Kaliumthiocarbonat gesprüht. Die Nachweisgrenze liegt zwischen 1,27 und 2,04g.

     

Die Extraktion von Thorium(IV), Protactinium(V), Uran(VI), Ruthenium(III) und Zirkonium(IV) mit langkettigen Aminen

Ohne Zusammenfassung     

Monohydrazido(2-)-complexes of molybdenum and tungsten (IV), (V) and (VI)

Summary Reaction of MoCl₅ or WCl₆ with 1-methyl-1-phenylhydrazine or 1, 1-diphenylhydrazine hydrochloride results in the formation of M^VI species [MCl₄(NNRR)]. These react with tertiary phosphines PR₃ to form M^V species [MCl₃(NNRR)(PR₃) _n ] (n=1 or 2).[MoCl₃(NNMePh)(PMe₃)₂] can be reduced in the presence of PMe₃ to the Mo^IV speciescis-mer-[MoCl₂(NNMePh)(PMe₃)₃].