Soft chemistry synthesis of powders in the BaF2-ScF3 system

The BaF₂-ScF₃ system is studied using coprecipitation from aqueous solutions. Compound Ba₃Sc₂F₁₂ is found to form over a wide range (10–60 mol %) of scandium concentrations in the initial solution. At higher scandium concentrations in solution, a new phase of provisional composition BaSc₂F₈ · 2H₂O (hexagonal system, a = 9.6346 Å, c = 4.0483 Å) was obtained. Scandium fluoride hydrolysis is not observed by energy-dispersive X-ray analysis.     

Formation of scandium carbides and scandium oxycarbide from the elements at high-(P, T) conditions

Synchrotron diffraction experiments with in situ laser heated diamond anvil cells and multi-anvil press synthesis experiments have been performed in order to investigate the reaction of scandium and carbon from the elements at high-(P,T) conditions. It is shown that the reaction is very sensitive to the presence of oxygen. In an oxygen-rich environment the most stable phase is ScO_xC_y, where for these experiments x=0.39 and y=0.50-0.56. If only a small oxygen contamination is present, we have observed the formation of Sc₃C₄, Sc₄C₃ and a new orthorhombic ScC_x phase. All the phases formed at high pressures and temperatures are quenchable. Experimentally determined elastic properties of the scandium carbides are compared to values obtained by density functional theory based calculations.     

Preparative,infrared and thermogravimetric studies of three scandium 8-hydroxyquinolinates

The preparation of 3 scandium 8-hydroxyquinolinates is reported. Two were prepared by precipitation from homogeneous solution using 8-hydroxyquinoline generated by hydrolysis of 8-acetoxyquinoline, and the third by a solid-phase reaction. The first precipitate was obtained at pH 6.5 as a lemon-yellow compound with the composition ScQ₃.HQ (Q == C₉H₆NO). The second chelate was obtained at pH 8.8 as a bright-yellow compound of composition (ScQ₃)₂.HQ. The third scandium 8-hydroxyquinolinate was obtained by a solid-phase reaction between the lemon-yellow compound ScQ₃.HQ and 8-hydroxyquinoline. The orange compound has the composition (ScQ₃)₂.3HQ. Infrared spectra and pyrolysis curves indicated that the 3 chelates have very similar structures.     

Scandium terminal imido complex induced intramolecular C–N bond cleavage and transformation

<正>1 X-ray crystallography Suitable single crystal of 2 was sealed in a thin-walled glass capillary, and data collection was performed at 293(2) K on a Bruker SMART diffractometer with graphite-monochromated Mo Kα radiation(λ = 0.71073 ). Suitable single crystals of 3and 4 were mounted under nitrogen atmosphere on a glass fiber, and data collection was performed at 133(2) K on a Bruker APEX2 diffractometer with graphite-monochromated Mo Kα radiation(λ = 0.71073 ). The SMART program package was used to determine the unit cell parameters. The absorption correction was applied using SADABS. The structures were solved     

Lewis acid catalyzed reactions of donor-acceptor cyclopropanes with 1- and 2-pyrazolines: formation of substituted 2-pyrazolines and 1,2-diazabicyclo[3.3.0]octanes

The reaction of 2-substituted cyclopropane-1,1-dicarboxylates with 1- and 2-pyrazolines is efficiently catalyzed by scandium or ytterbium triflates to give N-substituted 2-pyrazolines or 1,2-diazabicyclo[3.3.0]octanes. The reactions of 2-pyrazolines give diazabicyclooctanes as the major products. In contrast, the reactions starting from 1-pyrazolines predominantly give N-substituted 2-pyrazolines, which become the major compounds obtained if an equimolar amount of GaCl₃ is used. A possible reaction mechanism is suggested.     

Regularities in the distribution of TTA and its scandium chelate into a series of ester solvents

The distribution ratios of TTA and its scandium chelate between aqueous perchlorate solutions (μ=0.1) and 15 ester solvents including ethyl acetate were determined at 25°. A good correlation was found between the distribution coefficients of TTA and the “solubility parameter” of the ester solvents. The relationship between the distribution coefficients of the scandium chelate (P_M) and those of TTA (P_HA) was shown to be, log P_M=n log P_HA+ const. The distribution of this chelate into another ester can thus be predicted.     

Asymmetric synthesis of 2-alkyl-4-hydroxycyclohex-2-en-1-ones by scandium(III) triflate-catalyzed fragmentation of 2-alkyl-3-iodo-1-oxocyclohexan-2,4-carbolactones

Fragmentation of (2S,3S,4S)-2-allyl-3-iodo-1-oxocyclohexan-2,4-carbolactone to (4S)-2-allyl-4-hydroxycyclohex-2-en-1-one, a chiral building block of (−)-platensimycin, proceeded efficiently by using scandium(III) triflate in DMF-H₂O (1:3) at 100 °C.     

Dehydrocoupling of boranes with amines using a scandium catalyst

The scandocene alkyl complex (C₅Me₅)₂ScCH₂SiMe₃ was found to be an efficient catalyst for the dehydrocoupling of the non-cyclic boranes, dicyclohexylborane and thexylborane, with amines under mild conditions. The reactions afforded the corresponding aminoboranes in high yields with good functional group tolerance. The stoichiometric reaction of scandium alkyl with amine led to the isolation of a scandium amide complex, which was shown to be an active species during the catalysis. Although a borane-coordinated scandium hydride was also obtained from the stoichiometric experiment, it was not involved in the catalytic cycle. In addition, kinetic studies provided insight into this intermolecular dehydrogenation reaction.     

The Synthesis and Structure of a Scandium Nitrate Hydroxy-Bridged Dimeric Complex Supported by Bipyridyl Ligands

The current discussion on whether scandium, yttrium and lanthanum should represent Group 3 in the Periodic Table or whether lutetium should replace lanthanum in the group has prompted us to further explore the structural chemistry of the Group 3 elements and compare the coordination numbers and coordination geometries adopted. The steric and electronic properties of the coordinated ligands have a major influence on the structures adopted. We report the synthesis and crystal structure determination of an unusual dinuclear scandium complex [(bipy)(NO₃)₂Sc(µ-OH)₂Sc(NO₃)₂(bipy)] obtained by the reaction of hydrated scandium nitrate with 2,2′-bipyridyl (bipy) in either ethanol or nitromethane. The crystal structure of the complex shows that the scandium centers are eight coordinate, and the structure obtained contrasts with related complexes found in the lanthanide series [Ln(bipy)₂(NO₃)₃] and [Ln(phen)₂(NO₃)₃] (phen = phenanthroline) and in [M(terpy)(NO₃)₃] (M = Sc, Er–Lu), where these complexes are all mononuclear.     

Theoretical insight into structural and electronic properties of cationic Scn+ (n=2-13): A benchmark study

Geometric, thermodynamic and electronic properties of cationic scandium clusters are studied. Geometric optimizations and stable spin states of Sc₂⁺ are assessed on high level ab-initio coupled cluster method CCSD(T) with different dunning correlation consistent basis sets (aug-cc-pVDZ, aug-cc-pVTZ and aug-cc-pVQZ). Then, 23 DFT functionals belonging to different classes are evaluated at 6-31G (d), LANL2MB, LANL2DZ and Def2-SVP basis sets, and the results are compared with the benchmarked coupled cluster calculations. Due to excellent correlation, PBEPBE/LANL2DZ was chosen to perform calculation of higher scandium cationic clusters Sc_n⁺ (n = 3-13). In addition, we explored relative stability, binding energies, second order energy differences, vertical ionization energies, vertical electron affinities and HOMO-LUMO gaps. Moreover, these results are also compared with the neutral scandium clusters.     

Extraction of scandium(III) by bis(diphenylphosphorylmethylcarbamoyl)alkanes

The extraction of trace amounts of scandium(III) from HCl,HNO₃, and HClO₄ solutions in the form of complexes with neutral polyfunctional organophosphorus compounds bis(diphenylphosphorylmethylcarbamoyl)alkanes [Ph₂P(O)CH₂C(O)NH]₂(CH₂) _n (n = 3, 5, 8) was studied. The effect of the structure of the extractant, the aqueous phase composition, and the nature of the organic solvent on the efficiency of transition of scandium(III) ions into the organic phase was considered, and the stoichiometry of the extracted complexes was determined. The studied ligands exhibit a higher extraction power toward scandium(III) ions than their analog Ph₂P(O)CH₂C(O)NHC₉H₁₉ containing only one bidentate carbamoylmethylphosphoryl moiety per molecule. Scandium(III) passes into the organic phase most efficiently in the presence of HClO4 in the aqueous phase. It was shown that scandium(III) can be selectively recovered and preconcentrated by a complexing adsorbent obtained by noncovalent immobilization of bis(diphenylphosphorylmethylcarbamoyl)pentane on a macroporous polymer matrix.     

Structure of ScBr3 and Sc2Br6 molecules determined by the synchronous gas-phase electron diffraction and mass spectrometric experiment and quantum chemical calculations

The structure of monomeric and dimeric molecules of scandium tribromide is studied by the synchronous electron diffraction and mass spectrometric experiment at T = 888(10) K and also by the quantum chemical calculations. The experimental data on the structural parameters of ScBr₃ molecule were obtained for the first time; also for the first time the molecular structure of Sc₂Br₆ dimeric molecule was studied. It is found that the ScBr₃ molecule has the C _3v effective configuration with the distance r _g (Sc-Br) = 2.430(3) Å and the valence angle ∠_g(Br-Sc-Br) = 117.6(5)°. The equilibrium structure of the given molecule is planar with D _3h symmetry. According to a theoretical study by DFT and MP2 methods, Sc₂Br₆ molecule has the equilibrium structure of D _2h symmetry with four Sc-Br bridge bonds. It was confirmed by the results of the electron diffraction analysis.     

A Mössbauer spectroscopy investigation of SrFe1−xScxO3−δ perovskites

Polycrystalline samples of oxygen deficient perovskites SrFe_1?xSc_xO_3?δ (0 ≤ x ≤ 0.5) have been synthesized by direct solid state reactions. Each compound has been stabilized with two different oxygen stoichiometries. The structural study shows, firstly, the good cationic homogeneity of the samples and, secondly, that the Sc and Fe atoms are randomly distributed over the same crystallographic site, whatever the scandium content. This implies that no anionic order is possible. A detailed Mossbauer spectroscopy study clearly shows that the substitution of scandium for iron involves an oxygen content decrease which decreases the tetravalent iron content until its total disappearance for x = 0.5. The evolutions of the isomer shift, the quadrupolar splitting and the relative intensity versus the Sc³⁺ content are depicted in the present paper.     

Synthesis and molecular and crystal structure of the coordination metallopolymer of scandium(III) nitrate with 4,4,10,10-tetramethyl-1,3,7,9,-tetraazospiro[5.5]undecane-2,8-dione

{[Sc₂(C₁₁H₂₀N₄O₂)₃(H₂O)₆]⁶⁺ · 6(NO ₃ ^? )} _n (I), a coordination metallopolymer, has been synthesized for the first time and analyzed by X-ray diffraction. Crystals are tetragonal, space group P $\bar 4$ 2₁ c, a = 21.9797(6) Å, c = 12.7499(6)Å, V = 6159.6(4) ų, ρ_calcd = 1.392 g/cm³, Z = 4. The scandium atom is coordinated to the three oxygen atoms of spirocarbone molecules, which are related to the basal molecules by the symmetry codes 3/2 ? y, 3/2 ? x, 1/2 + z and 3/2 ? y, 3/2 ? x, ? 1/2 + z, and also to three water molecules. The coordination number of scandium is 6. The coordination polyhedron of scandium is a slightly distorted octahedron with OScO angles within 84.70(15)°–95.86(14)° and 172.77(16)°–173.84(15)°. Nitrate anions are in the outer coordination sphere of the metal. The purity of compound I is verified via the Rietveld refinement of its X-ray powder diffraction pattern; the unit cell parameters at room temperature are a = 22.0589(6) Å, c = 12.7806(6) Å, V = 6219.0(6) ų. Lines unrelated to the major phas are not observed in the X-ray diffraction pattern. The content of the major phase is 100 ± 1%.     

Phase equilibriums, oxygen exchange kinetics and diffusion in oxides CaZr1 ? x Sc x O3 ? x/2 ? δ

Oxides CaZr_{1 ? x} Sc _x O_{3 ? x/2 - ??} (x = 0.00?C0.20) were synthesized according to the ceramic technology. The solubility boundary of scandium with formation of solid solutions on the basis of calcium zirconate CaZrO_{3 ? ??} corresponds to x = 0.07?C0.08. The second phase of CaSc₂O₄ is present in the samples with scandium content of x = 0.10, 0.15, 0.20. Its fraction grows at an increase in x. The method of full-profile Rietveld analysis was used to calculate the structure parameters for oxides CaZr_0.99Sc_0.01O_{2.995 ? ??} and CaZr_0.95Sc_0.05O_{2.975 ? ??}. The method of isotopic exchange with gas phase analysis was used to study the kinetics of gas-phase oxygen interaction with the CaZr_0.95Sc_0.05O_{2.975 ? ??} oxide in the temperature range of 700?C850°C and at oxygen pressures of 0.13?C6.67 kPa. The values of effective activation energies of the oxygen exchange and diffusion processes were 1.36 ± 0.32 and 1.92 ± 0.21 eV, accordingly. The dependence of the interphase exchange rate on the pressure of oxygen corresponds to the power law with the exponent of 0.31 ± 0.04 at the temperature of 750°C.     

Formation of Metal Oxyfluorides from Specific Metal Reactions with Oxygen Difluoride: Infrared Spectroscopic and Theoretical Investigations of the OScF2 Radical and OScF with Terminal Single and Triple Sc?O Bonds

The scandium oxydifluoride free radical, OScF₂, is produced by the spontaneous, specific reaction of laser ablated Sc atoms with OF₂ in solid argon and characterized by using matrix infrared spectroscopy and theoretical calculations. The OScF₂ molecule is predicted to have C_2v symmetry and a ²B₂ ground state with an unpaired electron located primarily on the terminal oxygen atom, which makes it a scandium difluoride molecule coordinated by a neutral oxygen atom radical in forming the Sc? O single bond. The closed shell singlet OScF molecule with an obtuse bent geometry has a much shorter Sc? O bond of 1.682 Å than that of the OScF₂ radical (1.938 Å) on the basis of B3LYP calculations. The Sc? O bond in OScF consists of two covalent bonds and a dative bond in which the oxygen 2p_π lone pair donates electron density into an empty Sc 3d orbital thus forming a triple oxo bond. Density functional calculations suggest it is highly exothermic for fluorine transfer from OF₂ to scandium, which favors the formation of the OScF₂ radical species as well as the OScF molecule after fluorine loss.     

Preparation, morphology, and luminescent properties of europium-doped nanodispersed scandium sesquioxide

Scandium sesquioxide-based solid solutions of composition Sc_{2 ? 2x} Eu_2x O₃ (0.005 ?? x ?? 0.05) were prepared by thermolysis of Sc_{1 ? x} Eu _x (CH₃COO)₃ and by reacting mixtures of scandium and europium nitrates with ethylene glycol. Thermal decomposition of Sc_{1 ? x} Eu _x (CH₃COO)₃ was found to yield Sc_{2 ? 2x} Eu_2x O₃ with the shapes of aggregates atypical of the cubic structure of this oxide, and the reaction products of scandium and europium nitrates were found to have a loose spongelike structure. A spectroscopic study showed that Sc_{2 ? 2x} Eu_2x O₃ and Sc_{1 ? x} Eu _x (CH₃COO)₃ are potential luminescent materials active in the visible spectral region. The tervalent europium in the Sc_{2 ? 2x} Eu_2x O₃ structure is the source of strong red emission (⁵ D ₀ ?? ⁷ F ₂) and can be used in fluorescent lamps, colored lightning, and optoelectronic devices.     

Scandium 2-mercaptobenzothiazolate: Synthesis,structure and electroluminescent properties

The 2-mercaptobenzothiazolate scandium complex Sc(mbt)₃(THF) was obtained by the reaction of Sc[N(SiMe₃)₂]₃ with 2-mercaptobenzothiazole in THF. The X-ray diffraction analysis has shown that three flat mbt ligands coordinated to the metal center in η² fashion via N and exocyclic S atoms. To investigate the electronic structure and to interpret its electronic absorption and emission spectra, quantum chemical calculations of the complex at the B3LYP/TZVP DFT level have been performed with use of the Gaussian03 package. It was found that three higher occupied MO’s of the complex are ligand-localized while lower vacant MO’s contain a significant metal d contribution. Sc(III) complex was used as the emitter in the two-layer device with the configuration of indium tin oxide/N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine/Sc(mbt)₃/Yb, which exhibits EL emission at 550 nm.     

Preparation and characterization of scandia-doped tungsten powders prepared by a spray-drying method

Scandium oxide-doped tungsten powders were prepared by a new method of spray drying combined with two-step hydrogen reduction. The particle size of doped tungsten, powder morphology, and distribution of doped scandium oxide were characterized by scanning electron microscopy, X-ray diffraction, and laser diffraction particle size analysis. Experimental results indicated that the predecessor powders prepared by spray drying were spherical in shape. Two compounds, WO₃ and Sc₂W₃O₁₂, in the raw powder calcined at 600???C were transformed into metallic tungsten and scandia after reduction at 850???C by hydrogen for 1?h. The scandia-doped tungsten powders obtained had an average size of 950?nm and scandium oxide was distributed evenly throughout the tungsten powder. The mechanism of reduction of the doped tungsten oxide is discussed in this paper.     

Synthesis and characterization of substitutional solid solutions aLn2O3 · (1 − a)Bi2O3 · 4TiO2

The solubility of 10 lanthanide elements and of scandium is solid Bi₂Ti₄O₁₁ has been determined using Raman spectroscopy and X-ray diffraction. The data obtained were used to construct a diagram of solubility as a function of the ionic radii of bismuth and the lanthanide elements. The thermal stability of the solid solutions as a function of temperature and duration of thermal treatment has been qualitatively established.