Condensation of CF2Br2, CF2BrCl and BrCF2CF2Br with enamines and ynamines

BrCF₂X (X : Cl, Br, BrCF₂) react wth enamines and ynamines. A radical chain mechanism is proposed. Halogen (Br or Cl) - fluorine exchange of α halodifluoromethylketones to α trifluoromethylketones using Bu₄⁺N, F^?, 3H₂O is examined.     

Luminescence in near-thermal charge exchange. III. CH(+) and CD(+) A → X emission from He+ C2H2 and He+ + C2D2

A pulsed ICR cell fitted with synchronous photon counting equipment is used to investigate the emission produced between 185 and 500 nm by near-thermal charge exchange between He⁺ and C₂H₂ (C₂D₂). The emission bands observed are A ²Δ → X²π and (weakly) B²Σ^? → X²π in CH(CD) and A ¹π → X¹Σ in CH⁺(CD⁺). Wavelength measurements on the bandheads of the (0,0) and (0,1) bands of CD⁺ A → X are used to evaluate vibrational constants of CH⁺(CD⁺) X¹Σ⁺. The results are (in cm^?1): ω_e = 2869 ± 27 (2106 ± 20); ω_eχ_e = 65 ± 13 (35 ± 7). These constants are used to calculate Morse-potential Franck—Condon factors and vibrational branching ratios for CH⁺ and CD⁺ A → X emission. The spectral distributions and the (relatively low) absolute emission rates produced by He⁺/C₂H₂(C₂D₂) charge exchange are briefly discussed in the light of presently available information on the charge transfer reaction and on the excited states of C₂H_2?⁺     

Solubility of (UO2)3(PO4)2?4H2O in H+-Na+-OH?-H2PO?4-HPO2?4-PO3?4-H2O and Its Comparison to the Analogous PuO2 +2 System

The objectives of this study were to address uncertainties in the solubility product of (UO₂)₃(PO₄)₂⋅4H₂O(c) and in the phosphate complexes of U(VI), and more importantly to develop needed thermodynamic data for the Pu(VI)-phosphate system in order to ascertain the extent to which U(VI) and Pu(VI) behave in an analogous fashion. Thus studies were conducted on (UO₂)₃(PO₄)₂⋅4H₂O(c) and (PuO₂)₃(PO₄)₂⋅4H₂O(am) solubilities for long-equilibration periods (up to 870 days) in a wide range of pH values (2.5 to 10.5) at fixed phosphate concentrations of 0.001 and 0.01 M, and in a range of phosphate concentrations (0.0001–1.0 M) at fixed pH values of about 3.5. A combination of techniques (XRD, DTA/TG, XAS, and thermodynamic analyses) was used to characterize the reaction products. The U(VI)-phosphate data for the most part agree closely with thermodynamic data presented in Guillaumont et al.,⁽¹⁾ although we cannot verify the existence of several U(VI) hydrolyses and phosphate species and we find the reported value for formation constant of UO₂PO⁻₄ is in error by more than two orders of magnitude. A comprehensive thermodynamic model for (PuO₂)₃(PO₄)₂⋅4H₂O(am) solubility in the H⁺-Na⁺-OH⁻-Cl⁻-H₂PO⁻₄-HPO²⁻₄-PO³⁻₄-H₂O system, previously unavailable, is presented and the data shows that the U(VI)-phosphate system is an excellent analog for the Pu(VI)-phosphate system.     

Recombination energy of N22+

The recombination energy of N₂²⁺ has been computed using N₂²⁺, N₂²⁺ and N₂ potential curves from the literature. Vibrational overlaps and energies liberated in the various N₂²⁺³∑^?_g,¹∑_g⁺, ³Π_u, ¹Π_u → N₂⁺(X²∑⁺_g, A ²∑⁺_g, A ²Π_u, B²∑_u⁺,C²∑_u⁺) vibronic transitions have been computed and used as input for determination of the N₂⁺ recombination energy.     

Photodissociation of the dimer ions Ar+2, Ne+2, and (CO2)+2

The tandem quadrupole photodissociation mass spectrometer has been used to study photodissociation reactions of Ar⁺₂, Ne⁺₂, and (CO₂)⁺₂. The cross sections for photodissociation of Ar⁺₂ exhibited a strong dependence on ion source pressure, varying from 2 × 10 ^?18cm² at 0.1 torr to 6 × 10^?19cm² at 0.5 torr. A large photodissociation cross section (2 × 10^?17cm² for the reaction (CO₂)⁺₂ → CO⁺₂+ CO₂ was observed at the red end of the visible spectrum (580–620 nm) suggesting that this may be an important reaction in CO₂ rich planetary ionspheres such as that of Mars.     

Preparation and reactivity of the new cyclopentadienyl-bridged complex (Me2SiCH2CH2SiMe2)(C5H4Fe(CO)2)2

A new metal-metal bonded binuclear iron system [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)₂]₂ (2) has been prepared by treating two equivalents of NaCp with one equivalent of ClSi(Me)₂CH₂CH₂SiClMe₂ obtaining the intermediate (C₅H₅)Si(Me)₂CH₂CH₂Si(Me)₂(C₅H₅) which then is directly allowed to react with Fe(CO)₅ given 2 in 30% yield. From this cyclopentadienyldisilyl linked system three new binuclear irom complexes are formed. Treatment of 2 with Na/Hg in THF produced the dianion [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)₂^?]₂ which is quenched with CH₃I giving [Me₂SiCH₂CH₂SiMe₂][η⁵-C₄H₄Fe(CO)₂CH₃]₂ (4) in 76% yield. Complex 2 is oxidized with 1.2 equivalent of I₂ to give [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)₂I]₂ (5) in 85% yield. Photolysis of 5 (1 equiv.) and PPh₃ (3 equiv.) results in the formation of the bis-substituted compound [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)(PPh₃)I]₂ (6). These four new binuclear iron complexes are characterized by ¹H, ¹³C, and ³¹P NMR and IR spectroscopy.     

Rotational analysis of the 201 and 211 bands in the Ã2Σ+-X̃ 2Π spectrum of N2O+

Analysis of new emission spectra of òΣ⁺-X? ²Π in N₂O⁺, including the forbidden components with Δν₂ = 1, have made it possible to locate all four vibronic components of the ν″₂ = 1 manifold. Principal rotational constants and spinvibronic terms are given. A previous estimate of the Renner parameter is revised to a value of ?0.179 ± 0.002.     

Structure of uranyl complexes with acetylenedicarboxylic acid, K(H5O2)[UO2(OOCC≡CCOO)2 · H2O] · 2H2O and Cs2[UO2(OOCC≡CCOO)2 · H2O] · 2H2O

Uranyl complexes with acetylenedicarboxylic acid, K(H₅O₂)[UO₂L₂H₂O] · 2H₂O (I) and Cs₂[UO₂L₂H₂O] · 2H₂O (II), L²⁻ = C₄O ₄ ²⁻ were prepared for the first time. The composition and structure of the complexes were determined by X-ray diffraction. The crystal data are as follows: a = 16.254(12) ?, b = 13.508(8) ?, c = 7.683(6) ?, β = 90.91(7)°, space group C2/c, V = 1687(2) ?³ (I); a = 7.0745(10), b = 18.4246(10), c = 13.1383(10) ?, space group Abm2, V = 1712.5(3) ?³ (II). The structures of I and II are based on [UO₂L₂H₂O] _n ²⁻ anionic chains stretched along the [101] direction (I) or [010] direction (II). In I and II, the uranium coordination polyhedron is a pentagonal bipyramid in which the equatorial environment of the uranyl ions is formed by the oxygen atoms of the four L²⁻ anions and the water molecule. The L²⁻ anions in I and II are bidentate bridging ligands connecting two uranium atoms that are next to each other in the anionic chain; their coordination capacity is equal to 2. In I, the K⁺ and H₅O ₂ ⁺ cations are outer-sphere species. The latter form hydrogen bonds combining the anionic chains shifted by translation b with respect to each other. The [UO₂L₂H₂O] _n ²⁻ chains in I are surrounded by the potassium and oxonium cations; in II, these are combined by hydrogen bonds into anionic layers between which Cs⁺ cations are arranged. The IR spectrum of compound II was measured and interpreted. Original Russian Text ? I.A. Charushnikova, A.M. Fedoseev, N.A. Budantseva, I.N. Polyakova, Ph. Moisy, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 1, pp. 63–69.     

The A2Πu-X2Πg emission of I2+

A broad emission band found in helium, neon and argon afterglows in the presence of I₂, is attributed to I₂⁺ AX.     

Influence of Adding SiO2 into ZrO2 on SO2-4/ZrO2 Solid Superacid

用共沉淀法和负载法制备了一系列SO     

Electronic structure and reactivity of PO 43? , P2O 74? phosphate and SO 42? , S2O 72? sulfate anions

Group-theoretical analysis and molecular orbital methods were used to obtain (in analytical form) the electronic structure and reactivity of the PO ₄ ³⁻ , SO ₄ ²⁻ and P₂O ₇ ⁴⁻ , S₂O ₇ ²⁻ anions. The reactivity of the anions is dictated by the availability of lone electron pairs on the top quasidegenerate MOs in the form of linear combinations of group orbitals from atomic orbitals (AOs) of peripheral oxygen atoms for PO ₄ ³⁻ , SO ₄ ²⁻ and the central (bridging) atom for P₂O ₇ ⁴⁻ , S₂O ₇ ²⁻ . These electron pairs are responsible for the donor-acceptor interactions during complexation, clustering, and other (addition, substitution, etc.) reactions. Original Russian Text Copyright ? 2005 V. A. Zasukha, A. P. Shpak, V. V. Trachevskii, and E. V. Urubkova __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 3, pp. 405–415, May–June, 2005.     

ESR spectra and magnetic constants of α-Al2O3:Co2+,H+ and α-Al2O3 :Co2+,X+

New anisotropic ESR spectra of Co²⁺ doped sapphire, different from hitherto known, are reported. The new spectra which are observed, beside the well-known spectra of α-Al₂O₃:Co²⁺, are shown to form two sets, each one consisting of six spectra (1–6) and (7–12). The spectra of both sets are proven to be interrelated by B_3a symmetry. g and A tensors for each set will be given. Evidence is given that the two sets are to be assigned to the defects α-Al₂O₃:Co²⁺,H⁺ and α-Al₂O₃:Co²⁺,X⁺. The former is concluded to consists of a Co²⁺ ion at the substitutional site (c) and a proton located in a potential minimum along a straight line between O^2- ions situated in O²⁺ triangles above and below the CO²⁺ ion. The potential function for the proton has been calculated by quantum-chemical calculations to clucidate the geometrical structure of the paramagnetic center. The α-Al₂O₃:Co²⁺,X⁺ could not be fully analyzed but some evidence is presented, that X⁺ might be alkali ions.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

B2Au20/-/2-: 硼金团簇中的硼-硼多重键

采用密度泛函和波函数理论方法对B₂Au^20/-/2-的几何结构和电子结构进行研究. 计算结果表明阴离子B₂Au^2- ([Au-B B-Au]^-) (C_2h, ²A_u)和B₂Au^22- ([Au-B≡B-Au]^2-) (C_2h, ¹A_g)的基态结构均为线性结构, 即以含有多重键的BB单元(B B或B≡B)为中心, 两端各连接一个Au原子, 但两端的B－Au键不在同一直线上, 结构稍有变形; 而中性分子B₂Au₂ ([Au-B＝B-Au]) (D_∞h, ³Σ_g^-)的基态结构是以B＝B为中心, 两端各与一个Au原子相连的完美的线性结构. C_2h B₂Au^2-的单电子垂直剥离能和对称性伸缩振动频率的计算结果为实验表征提供依据.另外, 计算发现无机盐B₂Au₂Li₂结构中仍包含B≡B, 此结果一方面为其实验合成提供了可能性, 另一方面表明含有B≡B的B₂Au₂^2-结构极为稳定, 可作为结构单元存在于凝聚相中.     

Conductivity and thermogravimetric studies of HTi2NbO7 · 2H2O and CsTi2NbO7

A detailed study was performed of the interrelationships of the lattice parameters, ionic conductivity, and infrared spectrum of HTi₂NbO₇ · 2H₂O as a function of dehydration. We have shown that the oxide layers in this ion-exchange compound are interespaced with water layers 2-molecules thick, providing a rare example of a bilayer hydrate. Bulk proton transport occurs through these layers, with a conductivity of (8 ± 4) × 10^?6 ohm^?1cm^?1 at 20°C. Upon heating to 55°C, 0.5 H₂O per formula was gradually lost, but the conductivity was essentially retained. Upon further heating to 62°C another 0.5 H₂O was rapidly lost, resulting in a conductivity drop of a factor of 10. Further water was gradually lost until HTi₂NbO₇ was reached at 220°C. The X-ray evidence revealed no discrete, fixed-composition hydrate phases, indicating a single isostructural phase from HTi₂NbO₇ · 2H₂O to HTi₂NbO₇, with a single continuously variable interlayer spacing. The bulk conductivity of CsTi₂NbO₇ was less than 10^?8 ohm^?1cm^?1.     

ESR and structure of SO2Cl−√2

A single crystal ESR study is reported on the radial anion of sulphury chloride. In addition to the main spectrum which can be ananyzed in terms of anisotropic hyperfine coupling to two equivalent chlorines, the satellite spectrum of ³³SO₂Cl^?√₂ has been observed in natural abundance. The isotropic value of ca. 200 G for the ³³S hyperfine splitting corresponds to a spin population of 0.21–0.24 in the 3s orbital of sulphur. From the anisotropic chlorine coupling, a spin population of 0.31 in the 3p orbital on each chlorine atom has been derived. These results are consistent with a C_2v trigonal-bipyramid structure, the unpaired electron occupying a molecular orbital of a₁ representation which is localized to a considerable extent in the σ orbitals of the chlorine ligands in the apical positions. A similar structure is indicated by other results for certain isoelectronic phosphorus-centered radicals.     

Preparation and structure of NaSr0.5Al2B2O7 and NaCa0.5Al2B2O7

Two compounds NaSr_0.5Al₂B₂O₇ and NaCa_0.5Al₂B₂O₇, have been found to crystallize into a new structure type by Rietveld refinement from X-ray powder diffraction data. Their structure belongs to hexagonal space group P6₃/m, with lattice parameters of , for NaSr_0.5Al₂B₂O₇ and , for NaCa_0.5Al₂B₂O₇, respectively. The structure is built up by [Al₂B₂O₇]²⁻ double layer and Na⁺/Ca²⁺ or Na⁺/Sr²⁺ ions alternatively stacking along the c-axis. The sites in the inter-double layer are fully occupied jointly by Na and Ca or Sr, but the intra-double layer sites are only half occupied solely by Na. A mechanism of the transition of the structure from CaAl₂B₂O₇ to present structure type by replacing only 1% Ca by Na (2%) as observed by Chang and Keszler (Mater. Res. Bull. 33 (1998) 299) is also proposed.     

Syntheses, structures, optical properties, and theoretical calculations of Cs2Bi2ZnS5, Cs2Bi2CdS5, and Cs2Bi2MnS5

Three new compounds, Cs₂Bi₂ZnS₅, Cs₂Bi₂CdS₅, and Cs₂Bi₂MnS₅, have been synthesized from the respective elements and a reactive flux Cs₂S₃ at 973 K. The compounds are isostructural and crystallize in a new structure type in space group Pnma of the orthorhombic system with four formula units in cells of dimensions at 153 K of a=15.763(3), b=4.0965(9), c=18.197(4) Å, V=1175.0(4) Å³ for Cs₂Bi₂ZnS₅; a=15.817(2), b=4.1782(6), c=18.473(3)  Å, V=1220.8(3)  ų for Cs₂Bi₂CdS₅; and a=15.830(2), b=4.1515(5), c=18.372(2) Å, V=1207.4(2) Å³ for Cs₂Bi₂MnS₅. The structure is composed of two-dimensional _∞²[Bi₂MS₅²⁻] (M=Zn, Cd, Mn) layers that stack perpendicular to the [100] axis and are separated by Cs⁺ cations. The layers consist of edge-sharing _∞¹[Bi₂S₆⁶⁻] and _∞¹[MS₃⁴⁻] chains built from BiS₆ octahedral and MS₄ tetrahedral units. Two crystallographically unique Cs atoms are coordinated to S atoms in octahedral and monocapped trigonal prismatic environments. The structure of Cs₂Bi₂MS₅, is related to that of Na₂ZrCu₂S₄ and those of the AMM′Q₃ materials (A=alkali metal, M=rare-earth or Group 4 element, M′= Group 11 or 12 element, Q=chalcogen). First-principles theoretical calculations indicate that Cs₂Bi₂ZnS₅ and Cs₂Bi₂CdS₅ are semiconductors with indirect band gaps of 1.85 and 1.75 eV, respectively. The experimental band gap for Cs₂Bi₂CdS₅ is ≈1.7 eV, as derived from its optical absorption spectrum.     

Crystal field effects on the magnetic behavior of Yb2V2O7 and Tm2V2O7

The bulk magnetic behaviors of the pyrochlores Yb₂V₂O₇ and Tm₂V₂O₇ were investigated. Calculated susceptibilities were adjusted to obtain the best fit to experimental data. A cubic crystal field Hamiltonian was used with B°₄ = ?0.633 and B°₆ = 0.000705 K for Yb³⁺ and B°₄ = 0.0297 and B°₆ = 0.000339 K for Tm³⁺. The calculated susceptibility for Yb³⁺ was found to be insensitive to the addition of an axial B°₂ parameter to the cubic Hamiltonian.     

High-pressure transitions in MgAl2O4 and a new high-pressure phase of Mg2Al2O5

Phase transitions in MgAl₂O₄ were examined at 21-27 GPa and 1400-2500 °C using a multianvil apparatus. A mixture of MgO and Al₂O₃ corundum that are high-pressure dissociation products of MgAl₂O₄ spinel combines into calcium-ferrite type MgAl₂O₄ at 26-27 GPa and 1400-2000 °C. At temperature above 2000 °C at pressure below 25.5 GPa, a mixture of Al₂O₃ corundum and a new phase with Mg₂Al₂O₅ composition is stable. The transition boundary between the two fields has a strongly negative pressure-temperature slope. Structure analysis and Rietveld refinement on the basis of the powder X-ray diffraction profile of the Mg₂Al₂O₅ phase indicated that the phase represented a new structure type with orthorhombic symmetry (Pbam), and the lattice parameters were determined as a=9.3710(6) Å, b=12.1952(6) Å, c=2.7916(2) Å, V=319.03(3) Å³, Z=4. The structure consists of edge-sharing and corner-sharing (Mg, Al)O₆ octahedra, and contains chains of edge-sharing octahedra running along the c-axis. A part of Mg atoms are accommodated in six-coordinated trigonal prism sites in tunnels surrounded by the chains of edge-sharing (Mg, Al)O₆ octahedra. The structure is related with that of ludwigite (Mg, Fe²⁺)₂(Fe³⁺, Al)(BO₃)O₂. The molar volume of the Mg₂Al₂O₅ phase is smaller by 0.18% than sum of molar volumes of 2MgO and Al₂O₃ corundum. High-pressure dissociation to the mixture of corundum-type phase and the phase with ludwigite-related structure has been found only in MgAl₂O₄ among various A²⁺B³⁺₂O₄ compounds.