锗分族元素二元团簇及其与Co形成的团簇离子

通过比较激光烧蚀E1/E2 (代表Ge/Sn， Ge/Pb和Sn/Pb) 和Co/E (E为Ge、Sn、Pb)混合样品形成的二元团簇负离子飞行时间质谱分布和谱峰的相对强度及形成的幻数团簇离子峰，发现E1/E2二元团簇离子中原子量大的锗分族元素在团簇离子中占主要组分，而原子量小的元素则少量掺杂，其组成和分布特点说明其结构和性质与纯E团簇离子相似，可能的结构为该类负离子团簇所有原子都在笼结构的骨架上；对于二元团簇离子GeSn9－、GePb9－和SnPb9－其结构可能是双帽反四棱柱构型，只是每个原子均为骨架的一部分.而对激光烧蚀过渡金属钴与锗分族元素的混合物的研究发现，反应形成了丰富的Co/E二元合金团簇负离子，分析发现该类簇离子为钴内包覆于E(锗分族元素)笼状结构.幻数离子CoGe10－、CoSn10－和CoPb10－可能具有双帽四角反棱柱结构，而CoPb12－可能具有二十面体构型，钴原子均为笼状结构的中心.     

The molecular structures of O-methylhydroxylamine, N-methylhydroxylamine, N,O-dimethylhydroxylamine and N,N,O-trimethylhydroxylamine in the gas phase,determined by electron diffraction

The molecular structures of O-methylhydroxylamine, N-methylhydroxylamine, N,O-dimethylhydroxylamine and N,N,O-trimethylhydroxylamine in the gas phase have been determined by electron diffraction. In each case, the principal conformer present had the anti conformation about the N-O bond, but the dimethyl- and trimethyl-hydroxylamines also had 20–30% of the syn conformer. The N-O bond lengths increase with methyl substitution, from 146.3(3) pm in NH₂OMe to 151.3(9) pm in Me₂NOMe; C-N bond lengths also increase, but C-O bond lengths show a decrease.     

Die Reduktion von TiIV, VV CrIII, MoVI, WVI, UVI und FeIII mit Na-Pb-Legierung

Ohne Zusammenfassung     

Synthesis of (4R,15R,16R,21S)- and (4R,15S,16S,21S)-rollicosin

A convergent synthesis of (4R,15R,16R,21S)-rollicosin (1) and (4R,15S,16S,21S)-rollicosin (2) was accomplished. Hydroxy lactone 6a and/or 6b were synthesized from 4-pentyn-1-ol, and α,β-unsaturated lactone 7 was synthesized from γ-lactone 8 and 5-hexen-1-ol. Inhibitory activity of these compounds was examined with bovine heart mitochondrial complex I.     

Conformational and thermodynamic studies of alkaline subhalides M2X (M = Li, Na, K, Rb; X = F, Cl, Br, I)

Alkaline subhalides M₂X (M = Li, Na, K, Rb; X = F, Cl, Br, I) were investigated using DMol software combined with thermostatistical techniques to obtain thermodynamic data for studying the stability of these subhalides. Validation of these results was checked by establishing a link with the experimental MX-M phase diagrams by a simple empirical relation.     

Die papier-chromatographische Trennung von CrIII, MnII, CoII, FeIII und NiII

Ohne Zusammenfassung     

p, T, x, y data of benzene + n-hexane and cyclohexane + n-heptane systems

The isothermal vapour—liquid equilibria of the benzene + n-hexane and cyclohexane + n-heptane systems have been studied using a dynamic method. The thermodynamic consistency of the data has been tested and the prediction from several empirical and semitheoretical models have been compared with the experimental values of different excess properties.     

Synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate

The first total synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate has been achieved in seven steps and in 16% overall yield. The synthesis confirmed the assigned structure of this polyunsaturated natural product.     

Vibrational analysis of n-butyl, n-pentyl,and n-hexyl fluorides

Infrared spectra were obtained for n-butyl, n-pentyl, and n-hexyl fluorides in the liquid and solid states, and liquid-state Raman spectra were obtained for the first two of these. Normal coordinate calculations were carried out and twenty force constants of the C-CH₂F group were refined to provide the best fit for the 114 assigned frequencies of trans-n-propyl, gauche-n-propyl, TT-n-butyl, and TG-n-butyl fluorides. The resulting force constants were used to calculate the frequencies of the GT- and GG conformations of n-butyl fluoride and the two conformations for each of n-pentyl and n-hexyl fluoride that have coplanar carbon chains. The presence of all four conformers of n-butyl fluoride in the liquid state is indicated, but only the TG-conformer is present in the solid. The existence of the two conformations of n-pentyl and n-hexyl fluorides for which calculations were made is supported by comparison of the observed and calculated frequencies. Additional conformations seem to be present. The simplest solid-state spectrum is due only to the conformer that has a coplanar chain of carbons and the fluorine atom in the gauche position. Previous tentative conclusions about the relation between C-F stretching frequency and configuration have been revised.     

Syntheses, structure, and magnetic properties of several LnYbQ3 chalcogenides, Q=S, Se

The six LnYbQ₃ compounds β-LaYbS₃, LaYbSe₃, CeYbSe₃, PrYbSe₃, NdYbSe₃, and SmYbSe₃ have been synthesized from high-temperature solid-state reactions of the constituent elements at 1223 K. The compounds are isostructural to UFeS₃ and crystallize in the space group Cmcm of the orthorhombic system with four formula units in a cell. Cell constants (Å) at 153 K are: β-LaYbS₃, 3.9238(8), 12.632(3), 9.514(2); LaYbSe₃, 4.0616(8), 13.094(3), 9.932(2); CeYbSe₃, 4.0234(5), 13.065(2), 9.885(1); PrYbSe₃, 4.0152(5), 13.053(2), 9.868(1); NdYbSe₃, 4.0015(6), 13.047(2), 9.859(1); SmYbSe₃, 3.9780(9), 13.040(3), 9.860(2). The structure is composed of layers of YbQ₆ (Q=S or Se) octahedra that alternate with layers of LnQ₈ bicapped trigonal prisms along the b-axis. Because there are no Q-Q bonds in the structure the formal oxidation states of Ln/Yb/Q are 3+/3+/2−. Magnetic susceptibility measurements indicate that CeYbSe₃ and SmYbSe₃ are Curie-Weiss paramagnets over the temperature range 5-300 K.     

Ab Initio Study of Conformational Properties of ( Z, Z)-, ( E, Z)-, and ( E, E)-Cyclonona-1,5-dienes

Summary. Ab initio calculations at the HF/6-31G^* level of theory for geometry optimization and MP2/6-31G^*//HF/6-31G^* for a single point total energy calculation are reported for the important energy-minimum conformations and transition-state geometries of (Z,Z)-, (E,Z)-, and (E,E)-cyclonona-1,5-dienes. The C₂ symmetric chair conformation of (Z,Z)-cyclonona-1,5-diene is calculated to be the most stable form; the calculated energy barrier for ring inversion of the chair conformation via the C_s symmetric boat-chair geometry is 58.3kJmol^–1. Interconversion between chair and twist-boat-chair (C₁) conformations takes place via the twist (C₁) as intermediate. The unsymmetrical twist conformation of (E,Z)-cyclonona-1,5-diene is the most stable form. Ring inversion of this conformation takes place via the unsymmetrical chair and boat-chair geometries. The calculated strain energy for this process is 63.5kJmol^–1. The interconversion between twist and the boat-chair conformations can take place by swiveling of the trans double bond with respect to the cis double bond and requires 115.6kJmol^–1. The most stable conformation of (E,E)-cyclonona-1,5-diene is the C₂ symmetric twist-boat conformation of the crossed family, which is 5.3kJmol^–1 more stable than the C_s symmetric chair–chair geometry of the parallel family. Interconversion of the crossed and parallel families can take place by swiveling of one of the double bonds and requires 142.0kJmol^–1.     

Triethylantimony(V) complexes with bidentate O,N-, O,O- and tridentate O,N,O′-coordinating o-iminoquinonato/o-quinonato ligands: Synthesis, structure and some properties

The novel triethylantimony(v) o-amidophenolato (AP-R)SbEt₃ (R = i-Pr, 1; R = Me, 2) and catecholato (3,6-DBCat)SbEt₃ (3) complexes have been synthesized and characterized by IR, NMR spectroscopy (AP-R is 4,6-di-tert-butyl-N-(2,6-dialkylphenyl)-o-amidophenolate, alkyl = isopropyl (1) or methyl (2); 3,6-DBCat is 3,6-di-tert-butyl-catecholate). Complexes 1–3 have been obtained by the oxidative addition of corresponding o-iminobenzoquinones or o-benzoquinones to Et₃Sb. The addition of 4,6-di-tert-butyl-N-(3,5-di-tert-butyl-2-hydroxyphenyl)-o-iminobenzoquinone to Et₃Sb at low temperature gives hexacoordinate [(AP-AP)H]SbEt₃ (4) which decomposes slowly in vacuum with the liberation of ethane yielding pentacoordinate complex [(AP-AP)]SbEt₂ (5). [(AP-AP)H]²⁻ is O,N,O′-tridentate amino-bis-(3,5-di-tert-butyl-phenolate-2-yl) dianion and [(AP-AP)]³⁻ is amido-bis-(3,5-di-tert-butyl-phenolate-2-yl) trianion. The decomposition of 4–5 accelerates in the presence of air. o-Amidophenolates 1 and 2 bind molecular oxygen to give spiroendoperoxides Et₃Sb[L-iPr]O₂ (6) or Et₃Sb[L-Me]O₂ (7) containing trioxastibolane rings. This reaction proceeds slowly and reaches the equilibrium at 15–20% conversion five times more than for (AP-R)SbPh₃ analogues. Molecular structures of 1 and 5 were determined by X-ray analysis.     

Syntheses, structure, magnetism, and optical properties of the interlanthanide sulfides δ-Ln2−xLuxS3 (Ln=Ce, Pr, Nd)

δ-Ln_2−xLu_xS₃ (Ln=Ce, Pr, Nd; x=0.67-0.71) compounds have been synthesized through the reaction of elemental rare-earth metals and S using a Sb₂S₃ flux at 1000 °C. These compounds are isotypic with CeTmS₃, which has a complex three-dimensional structure. It includes four larger Ln³⁺ sites in eight- and nine-coordinate environments, two disordered seven-coordinate Ln³⁺/Lu³⁺ positions, and two six-coordinate Lu³⁺ ions. The structure is constructed from one-dimensional chains of LnS_n (n=6-9) polyhedra that extend along the b-axis. These polyhedra share faces or edges with two neighbors within the chains, while in the [ac] plane they share edges and corners with other chains. Least square refinements gave rise to the formulas of δ-Ce_1.30Lu_0.70S₃, δ-Pr_1.29Lu_0.71S₃ and δ-Nd_1.33Lu_0.67S₃, which are consistent with the EDX analysis and magnetic susceptibility data. δ-Ln_2−xLu_xS₃ (Ln=Ce, Pr, Nd; x=0.67-0.71) show no evidence of magnetic ordering down to 5 K. Optical properties measurements show that the band gaps for δ-Ce_1.30Lu_0.70S₃, δ-Pr_1.29Lu_0.71S₃, and δ-Nd_1.33Lu_0.67S₃ are 1.25, 1.38, and 1.50 eV, respectively. Crystallographic data: δ-Ce_1.30Lu_0.70S₃, monoclinic, space group P2₁/m, a=11.0186(7), b=3.9796(3), c=21.6562(15) Å, β=101.6860(10), V=929.93(11), Z=8; δ-Pr_1.29Lu_0.71S₃, monoclinic, space group P2₁/m, a=10.9623(10), b=3.9497(4), c=21.5165(19) Å, β=101.579(2), V=912.66(15), Z=8; δ-Nd_1.33Lu_0.67S₃, monoclinic, space group P2₁/m, a=10.9553(7), b=3.9419(3), c=21.4920(15) Å, β=101.5080(10), V=909.47(11), Z=8.     

Ab Initio Study of Conformational Properties of ( Z, Z)-, ( E, Z)-, and ( E, E)-Cyclonona-1,5-dienes

Ab initio calculations at the HF/6-31G^* level of theory for geometry optimization and MP2/6-31G^*//HF/6-31G^* for a single point total energy calculation are reported for the important energy-minimum conformations and transition-state geometries of (Z,Z)-, (E,Z)-, and (E,E)-cyclonona-1,5-dienes. The C₂ symmetric chair conformation of (Z,Z)-cyclonona-1,5-diene is calculated to be the most stable form; the calculated energy barrier for ring inversion of the chair conformation via the C_s symmetric boat-chair geometry is 58.3kJmol^–1. Interconversion between chair and twist-boat-chair (C₁) conformations takes place via the twist (C₁) as intermediate. The unsymmetrical twist conformation of (E,Z)-cyclonona-1,5-diene is the most stable form. Ring inversion of this conformation takes place via the unsymmetrical chair and boat-chair geometries. The calculated strain energy for this process is 63.5kJmol^–1. The interconversion between twist and the boat-chair conformations can take place by swiveling of the trans double bond with respect to the cis double bond and requires 115.6kJmol^–1. The most stable conformation of (E,E)-cyclonona-1,5-diene is the C₂ symmetric twist-boat conformation of the crossed family, which is 5.3kJmol^–1 more stable than the C_s symmetric chair–chair geometry of the parallel family. Interconversion of the crossed and parallel families can take place by swiveling of one of the double bonds and requires 142.0kJmol^–1.     

Syntheses, structures, physical properties, and electronic structures of KLn2CuS4 (Ln=Y, Nd, Sm, Tb, Ho) and K2Ln4Cu4S9 (Ln=Dy, Ho)

Seven new quaternary metal sulfides, KY₂CuS₄, KNd₂CuS₄, KSm₂CuS₄, KTb₂CuS₄, KHo₂CuS₄, K₂Dy₄Cu₄S₉, and K₂Ho₄Cu₄S₉, were prepared by the reactive flux method. All crystallographic data were collected at 153 K. The isostructural compounds KLn₂CuS₄ (Ln=Y, Nd, Sm, Tb, Ho) crystallize in space group Cmcm of the orthorhombic system with four formula units in cells of dimensions (Ln, a, b, c (Å)): Y, 3.9475(9), 13.345(3), 13.668(3); Nd, 4.0577(3), 13.7442(10), 13.9265(10); Sm, 4.0218(4), 13.6074(14), 13.8264(14); Tb, 3.9679(5), 13.4243(17), 13.7102(18); Ho, 3.9378(3), 13.3330(11), 13.6487(11). The corresponding R₁ indices for the refined structures are 0.0197, 0.0153, 0.0158, 0.0181, and 0.0178. The isostructural compounds K₂Dy₄Cu₄S₉ and K₂Ho₄Cu₄S₉ crystallize in space group C2/m of the monoclinic system with two formula units in cells of dimensions (Ln, a, b, c (Å), β (°)): Dy, 13.7061(13), 3.9482(4), 15.8111(15), 109.723(1); Ho, 13.6760(14), 3.9360(4), 15.7950 (16), 109.666(2). The corresponding R₁ indices are 0.0312 and 0.0207. Both structure types are closely related three-dimensional tunnel structures. The tunnels are filled with bicapped trigonal-prismatically coordinated K atoms. Their anionic frameworks are built from LnS₆ octahedra and CuS₄ tetrahedra. KLn₂CuS₄ contains _∞¹[CuS₃⁵⁻] chains of vertex-sharing tetrahedra and K₂Ln₄Cu₄S₉ contains _∞¹[Cu₄S₈¹²⁻] chains of tetrahedra. K₂Ho₄Cu₄S₉ shows Curie-Weiss paramagnetic behavior between 5 and 300 K, and has an effective magnetic moment of 10.71 μ_B for Ho³⁺ at 293 K. Optical band gaps of 2.17 eV for KSm₂CuS₄ and 2.43 eV for K₂Ho₄Cu₄S₉ were deduced from diffuse reflectance spectra. A first-principles calculation of the density of states and the frequency-dependent optical conductivity was performed on KSm₂CuS₄. The calculated band gap of 2.1 eV is in good agreement with the experimental value.     

NQR study of ternary chalcogenides A3BX3, ABX2, and ABX where A = Cu,Ag, or TI, B = As or Sb,and X = S or Se

¹²¹Sb, ¹²³Sb, ⁷⁵As, ⁶³Cu, and ⁶⁵Cu NQR resonances are reported for CuSbSe₂, Tl₃SbSe₃, Tl₃SbS₃, Tl₃AsS₃, Tl₃AsSe₃, Ag₃AsSe₃, TlSbS₂, CuAsS, AgAsS, and Cu₅SbS₃I₂. Tl₃SbSe₃ is an incongruently melting compound not observed in an earlier phase-diagram study of the pseudobinary system Tl₂SeSb₂Se₃. For isostructural arsenic and antimony chalcogenides the ratio of ⁷⁵As to ¹²¹Sb quadrupole coupling constants is 0.42, and for the BX₃ group in binary or ternary corresponding pairs of sulfide and selenides the ratio of quadrupole coupling constants for ⁷⁵As or ¹²¹Sb is 0.83. A reversible phase transition was observed at 130 K for Ag₃AsSe₃. Unit cell parameters are reported for crystals of TlSbS₂ and Cu₅SbS₃I₂.     

Preparation, structures, and properties of niobium chalcogenide halides, NbX2Y2 (X = S, Se; Y = Cl, Br, I)

The preparation of the compounds NbX₂Y₂ (X = S, Se; Y = Cl, Br, I). including that of large single crystals, by chemical transport techniques is reported. Most of these compounds exist in a triclinic low-temperature form and a monoclinic high-temperature form. The crystal structures of triclinic low-temperature NbSe₂Cl₂ and monoclinic NbS₂Cl₂ are reported; both structures consist of cage-shaped units of Nb₂X₄ which are linked together by the Cl atoms to form sheets parallel to the a, b planes. Both the Nb and the X atoms are present in pairs which indicates that the compounds can be formulated as Nb⁴⁺₂(X₂)²⁻₂₂Y⁻₄, in agreement with XPS spectra. The presence of Nb⁴⁺ in pairs explains the observed diamagnetic and semiconducting properties of NbX₂Y₂. The preparation and some properties of MoS₂Cl₂ (orthorhombic) are also given.     

Comparing the stability of tribenzo[ b , n , pqr ]perylene and tribenzo[ b , k , pqr ]perylene

Two isomeric benzenoid hydrocarbons – tribenzo[b,n,pqr]perylene and tribenzo[b,k,pqr]perylene played a crucial role in the formulation of the Clar aromatic sextet theory. The basic assumption of this theory is that tribenzo[b,n,pqr]perylene is more stable than tribenzo[b,k,pqr]perylene because the former has five, whereas the latter only four aromatic sextets. We now approach this stability problem from a different direction. By means of a recently developed molecular-orbital-based method it is possible to estimate the energy effects of individual cycles, as well as pairs, triplets, etc. of cycles in polycyclic conjugated molecules. From these energy-effects one can better understand which structural details are responsible for the thermodynamic stability of the underlying molecule. In particular, it is possible to rationalize (in a quantitative manner) the causes of differences in the thermodynamic stability of isomers. Our analysis corroborates the conclusion of Clar theory, but points out a number of hitherto overlooked structure-stability connections. Correspondence: Ivan Gutman, Faculty of Science, University of Kragujevac, P.O. Box 60, 34000 Kragujevac, Serbia.     

Ionization gauge sensitivities of N2, O2, N2O, NO, NO2, NH3, CClF3 and CH3OH

A Bayard-Alpert (BA) gauge was used to determine apparent relative sensitivites S_rel,X for O₂, N₂O, NO, NO₂, NH₃, CClF₃ and CH₃OH from gauge calibration measurements in the range 1.3×10^–1 Pap1.3·10^–3Pa. Nitrogen was used as a calibration standard.     

Comparing the stability of tribenzo[ b , n , pqr ]perylene and tribenzo[ b , k , pqr ]perylene

Two isomeric benzenoid hydrocarbons – tribenzo[b,n,pqr]perylene and tribenzo[b,k,pqr]perylene played a crucial role in the formulation of the Clar aromatic sextet theory. The basic assumption of this theory is that tribenzo[b,n,pqr]perylene is more stable than tribenzo[b,k,pqr]perylene because the former has five, whereas the latter only four aromatic sextets. We now approach this stability problem from a different direction. By means of a recently developed molecular-orbital-based method it is possible to estimate the energy effects of individual cycles, as well as pairs, triplets, etc. of cycles in polycyclic conjugated molecules. From these energy-effects one can better understand which structural details are responsible for the thermodynamic stability of the underlying molecule. In particular, it is possible to rationalize (in a quantitative manner) the causes of differences in the thermodynamic stability of isomers. Our analysis corroborates the conclusion of Clar theory, but points out a number of hitherto overlooked structure-stability connections.