Vol 64, No 10 (2019)

A new method to synthesize nanosized powders of gadolinium iron garnet was proposed, in which the precipitant is a strong base anion-exchange resin. The effect of the type of the resin (A400 or AV-17-8), the type of its counterion (OH or CO₃), and the temperature and duration of the process on the stoichiometry of the formed product and its yield was studied. The time–temperature parameters of gadolinium iron garnet crystallization were determined. The obtained products were investigated by X-ray powder diffraction analysis, thermal analysis, IR spectroscopy, and electron microscopy. Procedures were developed to produce precursors of stoichiometric composition, which, after annealing at 1000°C, form pure phase Gd₃Fe₅O₁₂ with a particle size of 20–40 nm according to transmission electron microscopy.

Lithium-rich superstoichiometric solid solutions MgLi_xMnO_3 – δ were obtained by intercalation into the spinel MgMnO_3 – δ using lithium hydride LiH as an intercalating agent through the stage of the formation of mechanocomposites. The accompanying chemical transformations involving the hydride ion were studied. Conventional ceramic synthesis methods and alternative intercalating agents were analyzed. It was shown that hydride intercalation produces pure samples of single-phase spinels with high lithium content (MgLi_0.75MnO₃), which is three times higher than that reachable by conventional ceramic synthesis methods.

A systematic study of copper(I)/copper(II) complexation with azaheterocyclic ligands and the boron cluster anions [B_nH_n]^2– (n = 10, 12) shows the possibility of synthesizing mononuclear, binuclear, trinuclear, tetranuclear, and polymeric copper(II) complexes. Here, we have studied copper(I) complexation with the [B₁₂H₁₂]^2– anion and azaheterocyclic ligands L (L = Bipy, BPA). The reaction have been carried out in air in organic solvents (CH₃CN and DMF). Under these conditions, copper(I) is oxidized, and mononuclear copper(II) complexes with ligands L and the [B₁₂H₁₂]^2– anion of different composition and structure are formed as final products. In addition, copper(II) complexes have been synthesized in the copper(I)/silver(I) system. The effects of the reaction conditions (the nature of the starting closo-dodecaborate, the source of copper(I), the presence of silver(I) compounds in the reaction solution) on the composition and structure of the final products have been shown. Reaction products have been identified by elemental analysis, IR spectroscopy, and X-ray diffraction. The structures of complexes [Ag(Bipy)₂]NO₃, [Cu(BPA)₂Cl]Cl · DMF, [Cu(BPA)₂Cl]₂ · 2DMF, [Cu(BPA)₂(DMF)₂][B₁₂H₁₂] · DMF, [Cu(BPA)₂][B₁₂H₁₂]]_n, and [Cu(Bipy)(DMF)₄][B₁₂H₁₂] have been determined by X-ray diffraction (CCDС nos. 1899332–1899337, respectively).

Triphenylantimony bis(3,3,3-trifluoropropanate) (I) to be converted into tetraphenylantimony 3,3,3-trifluoropropanate (II) after additional treatment with pentaphenylantimony has been synthesized by the reaction between triphenylantimony and 3,3,3-trifluoropropanoic acid (HL) in the presence of tert-butyl hydroperoxide. The hydrolysis of complex I leads to the formation of µ₂-oxo-bis(3,3,3-trifluoropropanatotriphenylantimony) (III). Complex II has also been synthesized from HL and pentaphenylantimony. The solvate Ph₄SbOC(O)CH₂CF₃ ⋅ HOC(O)CH₂CF₃ (IV) has been isolated from the reaction mixture at an acid excess (2 : 1 mol/mol). According to X-ray diffraction data, the Sb atoms in complexes II–IV have differently distorted trigonal bipyramidal coordination. The СSbO axial angles in complexes II and IV are 173.29(7)° and 178.06(11)°, respectively. In a centrosymmetric molecule of complex III (the inversion center is the bridging oxygen atom), the OSbO angles are 175.64(6)°. The Sb–O and Sb–С bond lengths are 2.255(2) and 2.109(2)–2.167(2) Å in II; 1.8169(3), 2.045(2) and 2.065(2)–2.403(3) Å in III; 2.319(3) and 2.110(4)–2.168(3) Å in IV. The Sb⋅⋅⋅O intramolecular distances with the carbonyl oxygen atom (3.414(3) Å (II), 3.232(4) Å (III), 3.233(4) Å (IV)) are ~0.3–0.5 Å smaller than the sum of the antimony and oxygen van der Waals radii.

The interaction of a terminal thiol group with gold clusters and Au₁₂M intermetallic clusters has been studied by quantum-chemical methods. The energy of addition of the SH group has been found to have the least value for the most stable of the known clusters, which do not change their structure upon addition of the SH group. The highest energy of addition of the terminal thiol group is accompanied with structural modifications of the initial cluster.

The review of the thermodynamic properties of complex lanthanide–zirconium oxides, namely, Ln₂Zr₂O₇ (Ln = La, Pr, Sm, Eu, Gd) with a pyrochlore structure and Ln₂O₃ · 2ZrO₂ solid solutions (Ln = Tb, Ho, Er, Tm) with a fluorite structure, is presented on the basis of our and literature data. The heat capacity was experimentally studied for Ln₂Zr₂O₇ (for the cerium subgroup lanthanides) with a pyrochlore structure (Fd3m) and Ln₂O₃ · 2ZrO₂ (for the yttrium subgroup lanthanides) with a fluorite structure (Fm3m), which were characterized by X-ray diffraction and elemental analyses, scanning electron microscopy, and adiabatic and differential scanning calorimetry. The temperature dependences of the thermodynamic functions (entropy, enthalpy change, and reduced Gibbs energy) were calculated within a broad range of temperatures from smoothed heat capacity values. The available thermodynamic data were compared, and some recommended values were given. The contribution of low-temperature magnetic transitions was taken into account for Ln₂Zr₂O₇ (Ln = Pr, Nd, Sm, Gd). The effect of the Schottky anomaly on the heat capacity of lanthanide compounds was analyzed.

Glass formation in the AlCl–(CH₃)₂SO–H₂O system was detected for the first time, the boundaries of the glass formation region were determined, and glass AlCl₃ · 2.9(CH₃)₂SO · 4.8H₂O was synthesized. The IR spectra of glass-forming solutions within the boundaries of the glass formation region and the glass AlCl₃ · 2.9(CH₃)₂SO · 4.8H₂O were recorded. It was concluded that (CH₃)₂SO enters the first coordination sphere of the aluminum ion through the oxygen atom. The glass AlCl₃ · 2.9(CH₃)₂SO · 4.8H₂O was studied by calorimetry, and its glass transition temperature was determined to be T_g = –32.3°C.

Composition, stability constants and rate constants of intramolecular redox decomposition of cerium(IV) complexes with anions of quinic \({{\left( {{\text{CHOH}}} \right)}_{3}}{{\left( {{\text{C}}{{{\text{H}}}_{2}}} \right)}_{2}}{\text{C}}\left( {{\text{OH}}} \right)\)COOH, lactic \({\text{C}}{{{\text{H}}}_{3}}{\text{CH}}\left( {{\text{OH}}} \right){\text{COOH,}}\) tartaric \({\text{HOOCCH}}\left( {{\text{OH}}} \right){\text{CH}}\left( {{\text{OH}}} \right){\text{COOH}}\), and citric \({\text{HOOCC}}{{{\text{H}}}_{2}}{\text{C}}\left( {{\text{OH}}} \right)\left( {{\text{COOH}}} \right){\text{C}}{{{\text{H}}}_{2}}{\text{COOH}}\) hydroxycarboxylic acids have been determined by spectrophotometry, photometry, pH and kinetic measurements in nitrate medium in pH range 0–3 at ionic strength \(I = 2\) and \(295.15\) K. A direct linear correlation between stability constant logarithms and negative logarithms of rate constants of intramolecular redox decomposition of the studied complexes, which is absent in sulfate medium, has been revealed. The noted correlation can be considered as appearance of free energy linear relationship principle in coordination chemistry.

An option for the homogeneous substitution of iron for cobalt, nickel, and manganese in solid solutions with a α-NaFeO₂-type layered structure formed in the system Li–Ni–Mn–Co–O was studied. Two sets of samples, namely, Li(Ni_0.33Mn_0.33Co_0.33)_1 –xFe_xO₂ and Li(Ni_0.60Mn_0.20Co_0.20)_1 –xFe_xO₂ (0 ≤ х ≤ 1), were prepared by combusting sucrose- or starch-based gels and characterized by X-ray powder diffraction. It is the first time that single-phase Li(Ni,Mn,Co,Fe)O₂ samples containing 15–20% Fe of the total amount of cations were prepared. The position of a metastable area of Li(Ni,Mn,Co,Fe)O₂ solid solutions with respect to the section LiNiO₂–LiMn_0.5Co_0.5O₂–LiFeO₂ was determined in the frame of the isobaric–isothermal tetrahedron LiNiO₂–LiMnO₂–LiCoO₂–LiFeO₂.