Vol 61, No 8 (2016)

The influence of the coordination sphere of [Ti(OC₄H₉)_4–x(O₂C₅H₇)_x] complexes, concentration in solution, and the ratio n(H₂O)/n(Ti⁴⁺) on the hydrolysis and polycondensation kinetics of the complexes, the stability of the resulting gels, the thermal behavior of then-formed xerogels, the shift of anatase–rutile phase transition temperature, and the microstructure of the product, was determined.

Sorption characteristics of synthetic calcium aluminosilicates (CAS) obtained in the multicomponent CaCl₂–AlCl₃–KOH–SiO₂–H₂O system are presented. The isotherms of Sr²⁺ sorption on CAS from aqueous solutions containing no additional salts were measured for Sr²⁺ concentration from 0.5 to 11.1 mmol/L and solid to liquid phase ratio S: L = 1: 100. The maximum sorption capacity of synthetic CAS was determined, the phase distribution constants of Sr²⁺ ions at different S: L ratios were found. The recoveries of Sr²⁺ ions from solutions containing 0.01 mol/L Ca(NO₃)₂ and from a solution simulating water of the Mayak plant sewage pond No. 11 were determined.

Complex (H₃O)₃(diquat)₆{[BiBr₅]}₆[BiBr₆] • 2H₂O (I) has been prepared by the reaction between [BiBr₆]^3– and diaqua(1,1'-diethylene-2,2'-bipyridynium dibromide) in 2 M HBr and has been characterized by X-ray diffraction. The anionic part of compound I is formed by coordination polymeric anions {[BiBr₅]^–}_n built of {BiBr₆} octahedral blocks, which are joined by the μ²-bridge bromide ligands into infinite zigzag chains. The resulting complex belongs to new structural type among bismuth halide complexes.

The complex [p-Tol₄Sb]⁺[p-Tol₄Sb(DMSO)]⁺[IrBr₆]^2– (I) has been synthesized by the reaction between tetra(para-tolyl)stibonium bromide and sodium hexabromoiridate(IV) in dimethyl sulfoxide. In a solution, complex I is slowly converted into [p-Tol₄Sb(DMSO)]⁺[IrBr₄(DMSO)₂]^– (II). The antimony atoms in the [p-Tol₄Sb]⁺ cation of complex I have a distorted tetrahedral coordination: СSbС angles are 106.5(3)°–111.1(3)°, and Sb–С bonds range within 2.083(7)–2.097(7) Å. The antimony atoms in [p-Tol₄Sb(DMSO)]⁺ cations have a distorted trigonal bipyramidal coordination to oxygen and carbon atoms in axial positions. The axial OSbC and equatorial СSbC angles are, respectively, 172.5(4)° and 107.6(3)°, 115.9(3)°, 120.0(3)° for I; 177.2(9)° and 113.7(9)°, 116.9(9)°, 117.8(9)° for II. The Sb–C and Sb–O distances are 2.086(7)–2.117(8) and 2.945(9) Å (I), 2.09(2)–2.16(2) and 2.60(2) Å (II). The trans-BrIrBr angles in the octahedral [IrBr₆]^2– and [IrBr₄(DMSO)₂]^– anions range within 178.79(3)°–179.49(3)° and 176.6(4)°–178.79(15)°, respectively. The Ir–Br distances are 2.4686(9)–2.4925(9) Å and 2.463(5)–2.500(4) Å, respectively, and the Ir–S distances are 2.291(7) and 2.340(5) Å.

The ability of K₂[B₁₂H₁₂], Cs₂[B₁₂H₁₂], and Tl₂[B₁₀H₁₀] molecules to act as the oxidant of n-octane in the gas phase has been considered in comparison with the O₂, HNO₃, and KNO₃ molecules. Calculations have been performed at the B3LYP/6-31G*//6-311+G* + LanL2Dz level. Notwithstanding the fact that model calculations of isolated K₂[B₁₂H₁₂], Cs₂[B₁₂H₁₂], and Tl₂[B₁₀H₁₀] molecules only approximately reflect the properties of solid K₂[B₁₂H₁₂], Cs₂[B₁₂H₁₂], and Tl₂[B₁₀H₁₀], such a consideration makes it possible to reveal the molecular analogue of the “salt” effect: the oxidative ability of mixed salts K₂[B₁₂H₁₂] • KCl, Cs₂[B₁₂H₁₂] • CsCl, and Tl₂[B₁₀H₁₀] • KNO₃, in terms of the difference of the electronic chemical potentials of the oxidant and reductant, as well as of estimated electron density transfer, turns out to be similar to the oxidative ability of pure K₂[B₁₂H₁₂], Cs₂[B₁₂H₁₂], and Tl₂[B₁₀H₁₀].

More than 20 М₆Al₃₈ isomers and several М₁₂Al₃₂ isomers for nitrogen- and phosphorus-substituted clusters with six and twelve dopant atoms M = N and P substituted for Al atoms in different positions at the surface of the aluminum cage and inside it have been studied by the density functional theory method. In the preferred N₆Al₃₈ isomer, all N atoms are substituted for Al atoms initially located in one outer layer of the cluster. In the course of geometry optimization, the nitrogen atoms are incorporated into positions in the neighboring intermediate layer, thus converting it into a 12-atom face consisting of three vertex-sharing adjacent six-membered rings with short N–Al bonds. For Р₆Al₃₈, a distribution of the dopant either in both surface layers or in the intermediate space between the surface layers and the inner core of the cluster is preferred. Optimization of alternative structures of the N₁₂Al₃₂ cluster with N atoms substituted for Al atoms in both outer layers is evidence in favor of the isomer in which the dopants are dispersed as separated monatomic anions N–. Together with their bridging Al atoms, these anions form the inner [N₁₂Al₁₄] cage with an unusual dumbbell-like structure in which the upper and lower halves are linked through N–Al bonds with the equatorial aluminum atoms. In the next low-lying isomer being ~23 kcal/mol higher on the energy scale, there is observed the “microclustering” of the dopant to form three covalently bonded diatomic dianions N₂^2-; the latter, together with the bridging Al atoms are combined into a [N₆Al₆] “subcluster” inside the severely distorted outer cage. In P₁₂Al₃₂, the aluminum cage is subjected only to moderate distortions: the phosphorus atoms remain in the outer layers and form two three-membered rings [Р₃]. The estimated energies of the model substitution reactions Al₄₄ + M₆ → M₆Al₃₈ + Al₆ (1) and Al₄₄ + 2M₆ → M₁₂Al₃₈ + 2A_l6 (2) demonstrate that all these reactions are exothermic; however, for the nitrogen-containing clusters, the decrease in energy with increasing number of substitutions increases from 66 (1) to 113 (2) kcal/mol, while in the case of phosphorus, it decreases from 45 (1) to 4 (2) kcal/mol. The results obtained for N₆Al₃₈, N₁₂Al₃₂, Р₆Al₃₈, and Р₁₂Al₃₂ are compared with the previous calculations for the C₆Al₃₈, C₁₂Al₃₂, Si₆Al₃₈, and Si₁₂Al₃₂ clusters.

A method was proposed for producing solid solutions in the CdSe–PbSe systems, which is based on heat and high pressure treatment. X-ray powder diffraction analysis showed the formation of substitutional solid solutions Cd_xPb_1–xSe with the NaCl structure, which contained 20, 40, 60, and 80 mol % cadmium selenide. The solid solutions were characterized by scanning electron microscopy, impedance spectroscopy, gas pycnometry, and Raman spectroscopy.

The thermal behavior of the gels that are formed in the synthesis of MgFe_1.6Ga_0.4О₄ powders was studied by differential scanning calorimetry and thermogravimetry (DSC–TG). The combustion temperatures of the gels in flowing air and flowing argon were determined from experimental data and thermodynamic calculations. The calculations of combustion temperatures from the heat flow of reaction versus time are shown to be a reliable tool to determine the parameters of gel combustion.

Solubility was studied in the system NaCl–AlCl₃–HCl–H₂O at 25°C in the section 28 wt % HCl. The system is of the eutonic type and has an extensive sodium chloride crystallization region. The composition of the eutonic solution is the following, wt %: NaCl, 0.47; AlCl₃ • 6H₂O, 8.88; HCl, 25.38; and H₂O, 65.27. The lines of saturated solutions were approximated by polynomial equations.

Solubility at the invariant points of the Na,Са||SO₄,СО₃–H₂O system at 25°C was studied, and a solubility diagram at this temperature constructed.

The effects of various factors on the redox stability of the gold(I) sulfite complex Au(SO₃)₂^3- in acidic chloride solutions is studied. Increased concentrations of gold and H⁺, as well as temperature, reduce the time before traces of gold(0) emerge; increased concentrations of sulfite and especially of Cl^– increase this time. The beaker material (quartz, glass, or polypropylene) is found to have no significant effect. Added organic solvents have different effects. It is shown using UV spectroscopy and pH measurements that the average number of SO₃^2- ions bound to one gold(I) ion can be much greater than two even at an excessive amount of sulfite in the acidic region (pH 2–4) due to the equilibrium Au(SO₃)Cl^2– + SO₃^2- = Au(SO₃)₂^3- + Cl^– with the constant logK₂ = 6.4 ± 0.1 at 25°C and I = 1 M (NaCl).