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The electroanalytical characteristics of an ion-selective electrode (ISE) with a membrane based on a supramolecular polymer composition containing polyvinyl chloride, o-nitrophenyl octyl ether plasticizer, tetradecyphosphonium pertechnetate ionophore, and a lipophilic additive of tetradecylphosphonium tetraphenyborate are studied. The limit of detection for the ISE in aqueous solutions containing KTcO4 was 2 × 10–7 M and the slope of the electrode function at 20°C was 58 ± 1 mV/pTc $${\text{O}}_{4}^{ - }$$ . Potentiometric selectivity coefficients were determined for various anions. A correlation between the hydration energy ΔGhydr and selectivity coefficients calculated by the method of mixed solutions is observed. It was found that a change in the pH of the solution in the range 2–12 slightly affects the electrode potential when the concentration of Tc $${\text{O}}_{4}^{ - }$$ in the analyzed solution is 1 × 10–6–0.001 M. The behavior of the electrodes in strongly acidic solutions was studied.

The surface morphology and composition of a NbC/C composite prepared via thermal decomposition of the products of reaction between NbCl5 and acetylene [9] have been studied by scanning electron microscopy and X-ray photoelectron spectroscopy. The results demonstrate that the NbC thus synthesized consists of nanocrystals. The surface layer of the NbC/C composite contains nine carbon atoms per Nb atom. The niobium is present in the form of the NbC carbide (33%) and the NbO2 (10%) and Nb2O5 (57%) oxides, with Nb 3d5/2 electron binding energies of 203.8, 205.0, and 207.2 eV, which are tentatively attributed to Nb2+ (NbC), Nb4+, and Nb5+ ions, respectively. The presence of NbO2 and Nb2O5 in the surface layer is due to active reaction of the NbC/C composite with atmospheric oxygen and moisture during the sample preparation process. Our results on the structure of the C1s electron spectra lead us to assume that the carbon on the surface of the composite particles has the form of a graphene-like carbon material. The composite does not become charged when exposed to an X-ray beam, which suggests that it is a weak dielectric.

The first complexes of cerium tetrafluoride in solutions have been studied by 19F NMR and IR spectroscopy. The temperature dependence of the 19F NMR spectra has been explored, and conclusion has been made that dynamic equilibrium between the molecular adduct and singly charged ionic forms, including geometric isomers, exists in solution. The statistical probability for the formation of [CeF4(dmso)4] stereoisomers of square antiprism configuration has been calculated, and their assignment to possible stereoisomers have been made on the basis of relative intensities of the 19F NMR signals. Quantum-chemical calculations of the structure of one of the possible isomers have been performed for the [CeF4(dmso)4] molecular adduct, [CeF3(dmso)5]+ cation, and [CeF5(dmso)3]– anion to show their thermodynamic stability.

The complex formation of TiF4 with the phosphorylated ketone Ph2P(O)CH(Me)CH2C(O)Et (L), containing an asymmetric carbon atom in the aliphatic hydrocarbon group and representing a racemic mixture of enantiomers, was studied by 19F{1H} and 31P{1H} NMR spectroscopy. The composition of complexes formed in the solution was determined; analysis of the 19F NMR spectra resorting to the heterotropicity concept was used to assign the resonance lines to two chiral optically active racemic and meso-stereoisomers of cis-TiF4L2. The configurations of enantiomers of the monodentate ligand coexisting in the coordination sphere were found to have a crucial effect on the axial fluorine atoms of mixed octahedral cis-tetrafluoro d0 transition metal complexes. A new efficient method was developed for the synthesis of ligand L.

Some peculiarities of the effect of enantiomers of the monodentate ligand on the stereoisomerism of the mixed octahedral tetrafluoride complexes of d0-transition metals are established by the 19F{1Н} and 31Р{1Н} NMR methods for the complex formation of TiF4 with Ph2P(O)CH2CH(OH)Me (L) having the asymmetric carbon atom in the aliphatic hydrocarbon radical and being a racemic mixture of enantiomers in СН2Сl2. The compositions of the complexes formed in solutions are determined. The conclusion about the relative stereochemical configuration of the chiral and meso-stereoisomers of the geometric isomers of the TiF4L2 octahedral complex is based on an analysis of the 19F NMR spectra using the heterotropic concept.

The thermal behavior of hydroxylaminate uranyl complexes [UO2(NH2O)2(H2O)2] ‧ H2O, [UO2(NH2O)2], and [UO2(i-C3H7NHO)2(H2O)2] ‧ 2H2O has been studied. The complexes decompose at a low temperature (

Quantum-chemical calculations of the structure and relative thermodynamic stability of tetranuclear clusters MxN4 – xO6(OMе)10 (M, N = Re, Ru; x = 4–0) including geometric isomers of bimetallic clusters are performed to establish the possibility of replacing Re atoms by Ru atoms while maintaining a cyclic tetranuclear structure. As the initial model, the structure of Re4O6(OPri)10 was chosen which is an almost regular rhombus. The values of the metal–metal and metal–oxygen interatomic distances are calculated, and features of their variation under the transition from mononuclear to heteronuclear clusters and from neutral clusters to anions are discussed. Differences between the relative thermodynamic stability of homometallic and heterometallic tetranuclear clusters, including the geometric isomers of the latter, are discussed.

Effect of enantiomers of a monodentate ligand on the stereoisomerism of mixed octahedral cis-tetrafluoro complexes of d0 transition metals has been studied by 19F{1H} and 31P{1H} NMR by the example of TiF4 complexation in CH2Cl2 with Ph2P(O)CH2CH(OH)Me (L) containing asymmetric carbon atom in the aliphatic hydrocarbon group that constitutes a racemic mixture of enantiomers. Composition of complexes formed in solution has been determined, conclusion has been drawn on the relative stereochemical configuration of the chiral and meso stereoisomers of octahedral complex cis-TiF4L2 on the basis of analysis of 19F NMR spectra, using the heterotropism concept.

The compositions and structures of the products of the reaction of TaF5 with Ph2P(O)(CH2)2C(O)NМе2 (L) in СН3СN and СН2Сl2 are studied by the 19F and 31Р NMR methods. As the hydrocarbon bridge between the Р=О and С=О donor groups in carbamoylphosphine oxides elongates from –СН2– to (–СН2–)2, the chelation ability of the ligand is retained and the composition of the complexes formed in a solution is determined by the ratio of components. The compositions and structures of the hydrolysis products are studied. Distinctions in the coordination behavior of the considered ligand during complex formation with tantalum pentafluoride and titanium tetrafluoride are studied.

MALDI-TOF was used to study molybdenum dioxide (MoO2) containing a nanosized fraction. The composition of cationic clusters of nonstoichiometric lower molybdenum oxides in the gas phase was determined, and the thermodynamic stabilities and configurations of isomers were calculated for selected symmetric molecular structures and for cations MoSO 8 + and Mo5O 9 + . Molecular orbital analysis was performed for two trigonal-bipyramidal clusters Mo5O8 and Mo5O9. Changes in molybdenum–molybdenum interatomic distances in going from MoO 8 + and Mo5O 9 + cations to neutral clusters are discussed.

The reaction of TiF4 with PhP(O)[CH2C(O)NMe2]2 in CH2Cl2 has been studied by 19F NMR spectroscopy. It has been found that the major reaction products are chelate tetrafluoro complex (η2-L)TiF4 where the ligand is coordinated to the titanium ion through the P=O and C=O groups and cis-TiF4(ОР···L)2 where both ligands are coordinated to the central ion through the more basic P=O groups. Spectral features of the tetrafluoro chelate have been studied, which have been attributed for the first time to the appearance of a chiral center at chelate coordination. The character of manifestation of conformational isomerism of the chelate ring and chiral center in the chelating ligand in mixed octahedral complexes of d0 transition metal fluorides in 19F NMR spectra is discussed.

The first complexes of Ce(IV)fluoride in solution have been observed and studied by 19F{1H}, 1H NMR and IR spectroscopy in saturated solutions of CeF4*H2O in Me2SO diluted by CH3CN or CH2Cl2. On the base of analysis of the temperature dependence of the 19F{1H} NMR spectra and the assumption that the usual for the solid Ce(IV) fluorocomplexes square antiprism coordination polyhedron is retained in the solution, the conclusion has been made that dynamic equilibrium between the molecular adduct [CeF4(Me2SO)4] and ionic forms [CeF3(Me2SO)5]+ and [CeF5(Me2SO)3]− exists in solution, including geometric isomers. The statistical probability of formation of [CeF4(Me2SO)4] and [CeF5(Me2SO)3]− stereoisomers has been calculated. Quantum chemical calculations of the structures of some visually distinguishable isomers of [CeFn(Me2SO)8-n]4-n (n=3–5) and [CeF4(Me2SO)3(H2O)] showed their thermodynamic stability. The experimental IR spectrum of the solution is in a good agreement with calculated spectra of [CeFn(Me2SO)8-n]4-n and [CeF4(Me2SO)3(H2O)] stable complexes.

Molybdenum dioxide (Mo2) synthesized through thermal decomposition of the [MoO2(i-C3H7NHO)2] complex and containing a nanosized fraction has been studied by MALDI-TOF. The composition of clusters of lower nonstoichiometric molybdenum oxide cations in the gas phase has been determined, and theoretical calculations of the thermodynamic stability and structure of the isomers of the most symmetric structures have been performed. Molecular orbitals of the cationic and neutral clusters Mo5O8 and Mo5O9 have been examined, and the aromaticity of the Mo-Mo bonds in metallacycles has been demonstrated.

The surface composition and morphology of a carbon matrix/Mo2C composite have been studied by scanning electron microscopy and X-ray photoelectron spectroscopy. The results demonstrate that the carbon matrix has the form of entangled filaments of carbon nanotubes. The surface layer of the composite contains 57 carbon atoms per molybdenum atom. Molybdenum is present here in the form of the Mo2C carbide (39 at %) and the Mo2O5 (50 at %) and MoO2 (11 at %) oxides, with E b(Mo 3d 5/2) = 228.2, 229.6, and 231.9 eV, respectively. The presence of the Mo4+ and Mo5+ oxides in the surface layer is due to active reaction of the Mo2C in the composite with atmospheric oxygen and moisture during the sample preparation process and can be accounted for by the small particle size of the material. Based on analysis of the structure of the C 2s and C 2p valence electron spectra, we assume that the carbon nanotubes of the composite are graphitelike carbon structures. The composite studied here does not become charged when exposed to an X-ray beam, which suggests that it is a weak dielectric.

New complexes of uranyl with diethylglyoxime have been synthesized and studied. A feature of these complexes is the tetradentate bridging coordination of the ligand in both cis- and trans-conformations. The structure of organic ligand C6H12N2O2 and binuclear complex (CN3H6)4[(UO2)2(C6H10N2O2)(CO3)(C2O4)2] ∙ H2O have been determined by X-ray diffraction.

The products resulting from the reaction of TiF4 with Ph2P(O)(CH2)2C(O)Me (L') in CH2Cl2 have been studied by 19F{1H} and 31P{1H} NMR spectroscopy. At a twofold excess of L', solution contains cis-TiF4(L')2 (>90%), trans-TiF4(L')2, and fac-[TiF3L3']+, where L' is coordinated via the P=O group, as well as the dimer [(Ti2F7L'2)2]+, where L' is coordinated through the P=O and C=O groups. An equimolar solution contains dimeric and polynuclear complexes containing moieties with three terminal cis fluorine ions, while the other coordination sites are occupied by the P=O groups and F– bridges. At a twofold excess of TiF4, ligand L' coordinates via the P=O and C=O groups and behaves as a bridge along with F– ions. Thermodynamic stability of the structures of the TiF4L'2 isomers and the structure of [(µ-F)(µ-L')2(TiF3)2]+ has been calculated.

We have studied the spectroscopic properties and service performance of gadolinium hafnate and lutetium hafnate optical coatings. The coatings have been shown to possess improved optical parameters in comparison with binary oxide films and enhanced optical damage threshold

The composition and equilibria in solutions of the products of reaction of HfF4(dmso)2 with monodentate phosphoryl-containing bases L = Ph3PO, Bu3PO, and (Me2N)3PO in CH2Cl2 are studied by 19F NMR. Octahedral molecular complexes cis-[HfF4L2] and minor amounts of trans-[HfF4L2] and fac-[HfF3L3]+ cations were the main products for all ligands. The oxytrifluoride complex (μ-O)[HfF3(Bu3PO)2]2 and the [HfF5(Bu3PO)]– anion were identified in the case of Bu3PO. The conclusion about the formation of the hafnium oxytrifluoro complex was verified via hydrolysis of the product of reaction between HfF4 and Ph3PO upon exposure to air. As a result, (μ-O)[HfF3(Ph3PO)2]2 were detected; fine-structure 19F NMR resonance lines were obtained and the spin–spin coupling constant J FF was measured for the first time. Hydrolysis via adding a Bu4NOH solution in i-PrOH to the HfF4L2 solutions in CH2Cl2 did not yield the expected zirconium oxyfluoro complexes with the smaller number of fluorine atoms. Due to deeper hydrolysis, equilibrium in fluoride complexes shifted towards species with higher fluorine contents, [ZrF5L]– and [ZrF6]2–, resulting in the formation of Hf(O) x (OH) у (i-PrOH) z complexes that were not observed in the 19F NMR spectra and the substitution of the released fluoride ions for molecular ligands in HfF4L2 complexes.

The crystal structure of TiF4[(Ph2P(O)CH2CH2C(O)NMe2)] chelate (I) was studied by X-ray crystallography, which revealed four crystallographically independent complex molecules of similar structure (1–4). It was found that the molecules are only slightly different in the bond lengths between the coordinated atoms and the central titanium ion and considerably different in the geometry of the seven-membered TiOPCCCO chelate ring. The geometry of the chelate rings was found to be almost identical in each pair of complexes 1, 2 (A) and 3, 4 (B), and a conclusion was drawn on the presence of two conformational isomers (A and B) of the chelate complex. Quantum chemical calculations of the relative thermodynamic stability of molecules 1–4 were performed, and their geometry optimization led to one theoretical structure. The comparison of the chelate ring geometry in the theoretical structure and in conformers A and B revealed that the conformation of the theoretical chelate ring coincides with that of conformer A.

The thermal behavior of the molybdenum(VI) complex with N-isopropylhydroxylamine [MoO2(i-C3H7NHO)2] has been studied. The thermal decomposition of the complex has been found to proceed in a single stage at 185.5°C and to result in non-stoichiometric molybdenum(IV) dioxide.

The composition and structure of the products of the reaction of titanium tetrafluoride with Ph2P(O)(CH2)2C(O)NМе2 (L), the simplest representative of diphenyl[2-(N,N-dialkylcarbamoyl)ethyl]phosphine oxides, in a СН2Сl2 have been studied by 19F and 31P NMR. It has been shown for the first time that functionalized phosphine oxides form stable seven-membered chelate heterocycles on complexes of d° transition metals. On the basis of NMR data, previously unknown conformational isomerism of the seven-membered TiOPCCCO heterocycle in solution has been proposed. A simple and rather efficient method of synthesis of the ligand (L) from commercially available reagents has been developed.

Zirconium fluoro complexes with phosphoryl-containing bases (L) have been synthesized by the reaction of a suspension of ZrF4(dmso)2 in toluene with an excess of Ph3PO or Bu3PO, as well as (Me2N)3PO in CH2Cl2. The composition and structure of the complexes in CH2Cl2 solutions have been studied by 19F NMR in the temperature range 293–203 K. Phosphine oxides are substituted for dmso to form mainly cis-tetrafluoro species, insignificant amounts of trans-tetrafluoro species, and mer- and fac-[ZrF3L3]+ complexes. In addition to these species, the reaction with Bu3PO yields the dimeric oxo complex (µ-O)[ZrF3(Bu3PO)2]2. Hydrolysis of fluoro complexes in CH2Cl2 with the use of an NBu4OH solution in iso-PrOH does not lead to oxo and hydroxo complexes: first, the [ZrF5L]– complex is formed, and the final hydrolysis product is ZrF62-. The fine structure of 19F NMR resonance lines for the zirconium fluoride compounds [ZrF5L]–, cis- [ZrF4L2], dimeric oxo complex, and mer-[ZrF3L3]+ in organic solvents has been observed for the first time, which makes it possible to reliably identify the composition and structure of the zirconium coordination polyhedron in the complexes under consideration.

By precipitating from an aqueous solution of Ce(SO4)2·4H2O with 40 % hydrofluoric acid obtained a nanosized powder of cerium tetrafluoride hydrate with a composition close to CeF4*0.95 H2O. According to the results of x-ray phase analysis, the crystalline phase has a cubic lattice similar to lattice of PuF4·1.6H2O. The hydrate nanopowder is characterized by XRD, TEM, 1H and 19F{1H}NMR and IR - spectroscopy. Quantum chemical calculations of the IR- spectra of models of the possible interaction of water molecules with a fluorine ions have been carried out. The temperature behavior of the CeF4*0.95 H2O powder was studied by using X-ray powder diffraction analysis up to 300 °C and thermogravimetrically up to 200 °C.

The reaction of TiF4 with a twofold excess of Ph2P(O)CH2C(O)Me (L) (one of the simplest and, very likely, most practically interesting representatives of a new class of organophosphorus ligands—diorganylphosphorylalkanones) in CH2Cl2 has been studied.

Reactions of coordinated ligands in uranyl hydroxylaminate complexes with benzaldehyde were studied. Methods of the synthesis of uranyl complexes containing E and Z isomers of benzaldehydoxime were developed. The structures of [UO2((E)-C7H6NO)2{(CH3)2SO}2] and [UO2((Z)-C7H6NO)2{(CH3)2SO}2] were determined by X-ray diffraction.

We have studied the thermal stability of a MoCl1.9 ± 0.1C30 ± 1H30 ± 1 composite in vacuum (10 Pa) at temperatures from 70 to 1150°C. Using chemical and physicochemical analysis data (gas liquid chromatography, MALDI TOF mass spectrometry, and X-ray diffraction), we have identified the nature of the decomposition products of the composite. The solid residue after the decomposition has been shown to consist predominantly of hexagonal molybdenum carbide Mo2C, with finely dispersed carbon as an impurity phase. Volatile components have been identified as a mixture of alkyl-substituted anthracenes (phenanthrenes) and polycyclic hydrocarbons with saturated and aromatic rings. These results were used to gain insight into the structure of the hydrocarbon matrix of the composite.

The composition and structure of compounds formed upon the reaction of equimolar amounts of TaF5 and MeC(O)O(O)CMe in CH2Cl2 and upon dissolution of the fluoride in an anhydride excess have been studied by 19F NMR (293-183 K). It has been found that, in both cases, the anhydride is fluorinated to form MeC(O)F (a quartet at 47.7 ppm, JFH = 18 Hz) and the MeC(O)O− anion. In the spectra of the reaction mixture in CH2Cl2, the signals of pentafluoro complexes are assigned to the TaF5[OC(Me)OC(O)Me] adduct and the TaF5[OC(O)Me]− anion; on the basis of the chemical shifts of the singlets, they are assigned to the TaF4[OC(Me)OC(O)Me]+ and TaF2[OCOC(O)Me]23+ cations in which the anhydride acts as a chelating ligand. Upon the direct reaction of the reagents in an anhydride excess, the spectra at low temperatures show, in addition to the signal of the tetrafluoride cation, the signals of the hexafluorotantalate ion TaF6− and four trifluoroacetate complexes. Close relative concentrations of the latter enable the suggestion that they form chain or cyclic structures. It is believed that, in these structures, the acetate group has monodentate and bridging coordination modes, while chelating coordination mode seems to be less probable.

Ion-selective potentiometric sensors (ion selective electrodes, ISEs) based on tetradecylphosphonium hexafluoroarsenate are developed for the determination of AsF6− ions. Their main parameters, such as selectivity, linearity range of response, detection limit, and also the effect of pH on the readings of electrodes are evaluated. The developed electrode demonstrated high selectivity to the AsF6− acido-complex in the presence of various anions. The detection limit goes up with increasing concentration of HF; for fluoridefree neat solutions of LiAsF6, it is 3 × 10−7, pAsF6 = 6.52; at the concentrations of HF 0.1 and 4 M, it is 1.5 × 10−6 M, pAsF6 = 5.82, and 7 × 10−6 M, pAsF6 = 5.15, respectively.

Quantum-chemical calculations of the structures and thermodynamic stabilities of isomers of molecular clusters of lower Mo chlorides Mo13Cl24, Mo13Cl26, and Mo13Cl30, as well as of the Mo13Cl26− anion of cuboctahedral or icosahedral structure, have been performed by the DFT B3LYP method with the use of the Lanl2dz basis set for the Mo atoms and the 631G(d) basis set for the Cl atoms. The highest symmetry polyhedra are considered: Mo13Cl30 and Mo13Cl24 have a structure of centered icosahedron and cuboctahedron with bridging Cl atoms sitting atop the midpoints of 30 and 24 edges, respectively. In both cases, calculations lead to a rapid increase in the Mo-Mo distance to the values that are evidence of the absence of metal-metal bonds; hence, the cluster structure, in its classical meaning, is not retained. Both the neutral cluster Mo13Cl26 and the Mo13Cl26− anion—a symmetric icosahedron, in which Cl ions sit atop the centers of 20 faces and 6 Cl atoms are terminal, and a cuboctahedron, in which 14 Cl atoms are located on the three- and fourfold axes over the centers of molybdenum faces and 12 terminal Cl atoms are located on twofold axes. For both the neutral cluster and the anion, stable structures have been obtained. In both cases, the total energies are lower for the initial icosahedral configuration.

New molybdenum(VI) complexes with N-monoalkylsubstituted hydroxylamines have been synthesized and studied. The structure of [MoO2(C2H5NHO)2] and [MoO2(i-C3H7NHO)2], whose distinguishing feature is the bidentate chelate coordination of the ligand to molybdenum with the formation of the three-membered NMoO chelate ring, has been determined by X-ray diffraction.

It has been shown by the example of TiF4 complexes with α-picolinic acid (C5H5NCOOH, picH) and its esters (picEt and picSiMe3) in CH3CN that the 19F NMR chemical shifts can be used for estimating the basic properties of nonequivalent donor sites of chelating ligands. TiF4 reacts with picEt to form adducts: the TiF4(η2-picEt) chelate and trans-TiF4(picEt)2. The reaction of TiF4 with an equimolar amount of picH yields the cis-TiF4 (η2-picH) complex with three nonequivalent fluorine positions. The introduction of a ligand excess leads to a change in the chemical shifts of the fluoro complex, which is interpreted to be due to the formation of H-bonded complexes TiF4(η2-picH…picH). The introduction of Et3N, which binds protons, shifts the equilibrium toward the [TiF4(η2-pic)]− anion. The reaction of TiF4 with picSiMe3 occurs in an essentially different way. The major species in solution is the [(μ-F)(μ-OOpic)2(TiF3)2]− dimer. Its possible isomeric structures are discussed. On the basis of comparison of the chemical shifts of the fluorine atoms trans to the oxygen and nitrogen atoms of the chelate ligand, the conclusion has been drawn that the basicity of the chelate donor sites increases in the series (η2-picEt)TiF4 < (η2-picH)TiF4 < [(η2-pic)TiF4]− and that for all the complexes, the basicity of the nitrogen atom of the chelate is higher than that of the oxygen atom.

The reaction of tantalum pentafluoride with methyl isocyanate in dichloromethane was studied by 19F NMR and IR spectroscopy. The reaction was found to give bond isomers TaF5L, in which methyl isocyanate (L) is coordinated in the monodentate mode via N or O atom, and the heterocyclic cation [(μ-F)(μ-MeNCO)(TaF4)2]n+(n=1,2). On storage of the reaction mixture, a signal in the C-F bond region appears in the spectrum and other new signals appear, which were assigned to the formation of O- and N- bonded isomers of pentafluoro complex of tantalum with aminocarboxylic acid fluoride anions [FC(O)N(Me)TaF5]− and [N{Me)C(F)OTaF5]−, which can be considered as insertion of MeNCO into the Ta-F bond. The IR spectroscopy data support these assumptions.

19F and 21Sb NMR spectroscopy and chemical analysis were used to study the composition and structure of fluoride complexes of antimony(V) and tantalum(V) in organic and aqueous phases in extraction by tributyl phosphate (TBP) and n-octanol. It is found that extraction from solutions containing a single element or both elements occurs via the hydrate-solvate mechanism. The possibility of separating tantalum(V) and antimony(V) by extraction from fluoride solutions is shown. The efficiency of tantalum(V) and antimony(V) separation by extraction from fluoride solutions is enhanced at a transition from TBP to n-octanol.

The gas-phase niobium oxochloride anions that result by the interaction between the finely dispersed stereoselective acetylene cyclotrimerization catalyst NbCl2(CnHn) (n = 10–12) and atmospheric oxygen and moisture have been characterized by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. From the relative intensities of mass spectrometric lines, it has been deduced that, among the various niobium oxochloride species passing into the gas phase under the action of laser radiation, the most abundant monomer ion is NbO2Cl2−, the most abundant dimers are Nb2O4Cl3− and Nb2O3Cl5−, the most abundant trimer is Nb3O6Cl5−, and the most abundant tetramer is Nb4O8Cl5−. The gas phase also contains low concentrations of fragments corresponding to the pentanuclear anion Nb3O11Cl4− and the hexanuclear anion Nb6O15Cl2−. The geometric parameters and total energy of the stable isomers of the dinuclear and polynuclear niobium oxochloride anions existing in the gas phase has been calculated by quantum chemical methods, and their relative thermodynamic stabilities have been determined for different metal core configurations and different arrangements of oxygen and chlorine ions. The stereochemistry of the niobium oxochlorides is discussed.

A reaction of uranyl dioxalate complexes with methyl derivatives of alicyclic α-dioximes, 3-methyl-1,2-cyclohexanedione dioxime and 3-methyl-1,2-cyclopentanedione dioxime, was studied. The structure of (CN3H6)4[(UO2)2(C6H8N2O2)(CO3)(C2O4)2] · (C6H10N2O2) · 2H2O and NH4(CN3H6)3[(UO2)2(C7H10N2O2)(CO3)(C2O4)2] · 2H2O based on binuclear complex anions with carbonate-dioximate fragment was studied by X-ray diffraction.

The formation of uranium oxides by thermal decomposition of uranyl diaquadihydroxylaminate monohydrate, ammonium diuranate, ammonium tricarbonatouranylate, and uranium peroxide under the action of microwave (MW) radiation was studied. Uranium dioxide is formed by decomposition of these compounds in a reducing atmosphere at the MW radiation power of 600 W and treatment time of 5–10 min. In air, under the same conditions, U3O8 is formed. Under the action of MW radiation, substandard ceramic pellets of UO2 fuel can be readily converted in air to powdered U3O8. The use of MW radiation for thermal decomposition of uranium compounds allows the power and time consumption to be considerably reduced relative to the process with electrical resistance furnaces. A quick method for gravimetric testing of the composition of uranium oxides (UO2 or U3O8) using MW radiation was suggested.

The elemental and ionic compositions of the surface of NbCl2(C n H n ) (n = 10–12), an active catalyst for acetylene cyclotrimerization into benzene, have been determined by X-ray photoelectron spectroscopy. Binding energy data for the sample sputtered with argon ions E b (Nb3d 5/2) = 203.8–204.2 eV) suggest that the oxidation state of niobium in the active catalyst is +2 or +3. The narrow C1s line indicates the equivalence of all carbon atoms, and the corresponding binding energy, E b(C1s) = 284.0 eV, is close to the BE value for cyclic unsaturated hydrocarbons with conjugate double bonds. Interacting with atmospheric oxygen and moisture during sample preparation, niobium ions on the catalyst surface oxidize to their highest oxidation state, +5, characterized by E b (Nb3d 5/2) = 207.3–207.7 eV. These data suggest that niobium oxychlorides or oxides form ion the sample surface. The catalyst is stable in a high vacuum and undergoes slight charging under the action of an X-ray beam, showing poor dielectric properties.

It was shown that, in contrast to the Purex process using aggressive and environmentally hazardous 8M HNO3 solutions for dissolving spent oxide nuclear fuel (SNF), this fuel can be easily dissolved in aqueous subacid ([H+] ∼0.1 M) solutions of Fe(III) nitrate (chloride) with partial separation of uranium and plutonium from fission products (FP). The low acidity of the solutions obtained (pH ∼1) allows direct application of modern technologies of finishing processing of nuclear fuel by fluoride, carbonate, oxalate, or peroxide precipitation of uranium and plutonium. It was established that U(VI) is isolated from nearly neutral nitric acid solutions as a poorly soluble uranyl hydroxylaminate complex after adding hydroxylamine. It was shown that on thermal decomposition at 200–300°C under ambient atmosphere this compound converts into uranium dioxide. A similar approach was applied to obtain mixed oxide uranium-plutonium fuel (MOX fuel).

The surface of a MoCl2C30H30 composite in the form of molybdenum nanoclusters in a polyacetylene matrix, produced by reacting MoCl5 with C2H2 in benzene and toluene, has been studied by X-ray photoelectron spectroscopy before and after Ar+ ion milling. The composite actively reacts with atmospheric oxygen and moisture. As a result, the molybdenum clusters on its surface oxidize to molybdenum(V) or molybdenum(VI) oxides or oxychlorides (Eb(Mo 3d5/2) = 232.3–232.5 eV) during the sample preparation process. The electron binding energy of molybdenum affter surface etching (Eb(Mo 3d5/2) = 228.5 eV) suggests that the oxidation state of the molybdenum in the composite is 2+ or 3+. Analysis of the structure of the spectrum of the C 2s electrons of the inner valence molecular orbitals using the energy level diagram of the C2 molecule suggests that the hydrocarbon matrix of the composite contains, in addition to-CH=CH-CH=CH- conjugate bonds, linear carbyne fragments: -HC=C=CH- or -C≡C-. After etching, the surface layer of the composite contained argon, which might be due to adsorption because of the small particle size of the composite or chemisorption on the surface of the polyacetylene matrix. The composite is stable in a high vacuum of 1.3 × 10−5 Pa up to 350°C and does not experience charging when exposed to X-rays, which indicates that it has weak dielectric properties.

The reactions of coordinated ligands in uranyl complexes were studied for the first time. The reaction of uranyl hydroxylaminate complexes with aldehyde and ketones of different structure was shown to result in the formation of corresponding oxime complexes.

Molybdenum(VI) oxide MoO3 has been studied and the composition of polynuclear molybdenum oxides in the gas phase MoxO3x − y (x = 1–6, y = 0–2) has been determined by laser desorption/ionization time-of-flight mass spectrometry. Quantum-chemical calculations of bond energies, interatomic distances, charge distributions, and molybdenum-molybdenum bond orders for the isomers of neutral polynuclear molecular compounds MoxO3x − y have been performed with the use of the PBE functional with a relativistically corrected potential implemented as the PRIRODA program package. On the basis of the bond energies, the relative stability of the isomers has been estimated. For the MoxOy isomers (x ≥ 3), cyclic structures have been predicted to be more favorable. For the predicted most stable isomers of each MoxOy composition, the bond energies of their positive and negative ions have been calculated. The positive ionization of MoxOy leads to a considerable decrease in the bond energy of the isomer and the negative ionization, to its increase by about 0.1 au.

Uranyl complexes with ethylmethylglyoxime were studied. The structure of (CN3H6)4[(UO2)2(CO3)(C2O4)2(C5H8N2O2)] · 1.5H2O was determined by X-ray crystallography. The structure of the complex is binuclear with a double carbonate dioximate bridging fragment.

Addition of aqueous ammonia and hydroxylamine hydrochloride to a nitric acid solution containing U(VI) and Pu(VI) causes at pH ∼7 precipitation of a mixture of U(VI) hydroxylaminate and Pu(III) hydroxide. The precipitate separated from the mother liquor and dried at 60°C upon further calcination in air at 300°C transforms into a solid solution of PuO2 in UO2 as a result of thermal decomposition of the precipitate with the reduction of U(VI) to U(IV) by the ligand coordinated to the uranyl ion. The developed procedure for preparing mixed U-Pu dioxide can become an alternative to the presently used method for preparing uranium dioxide and mixed uranium-plutonium oxide fuel (MOX fuel) by heating at 800–900°C in a reducing atmosphere.

The cation influence on substitution reactions in aqua dioxalate uranyl complexes with the participation of a fluoride ion as an attacking ligand and two-charge cations of ethylene diammonium and propylene diammonium was considered. The structure of (C2H10N2)3[UO2(C2O4)2F]2 · 6H2O and (C3H12N2)[UO2(C2O4)2(H2O)] complexes was determined by X-ray crystallography.