环己硅烷类液晶化合物的量子化学研究

运用AM1和PM3两种SCF-MO方法，通过能量梯度全优化计算，给出20种环己硅烷类（苯基乙烷系）液晶化合物的稳定几何构型、电子结构和基本性质．联系有机电子结构理论进行了细致的讨论．     

Reactions of Ru3(CO)12 with Diphosphenes — A New Route to 50‐Electron Ru3P2 nido‐Clusters

The reaction of the symmetric diphosphene 2, 4, 6‐(CF₃)₃‐C₆H₂‐P=P‐C₆H₂‐2, 4, 6‐(CF₃)₃ 4 with Ru₃(CO)₁₂ led to the 50‐electron Ru₃P₂ nido‐cluster Ru₃(CO)₉[μ‐P‐C₆H₂‐2, 4, 6‐(CF₃)₃]₂ 5 , which in solution at room temperature displays hindered rotation of the aromatic rings about the C(aryl)—P bonds. The structure of 5 was determined by X‐ray crystal structure analysis; its Ru₃P₂ centre forms a distorted square pyramid with one ruthenium atom at the apex. One of the two C₆H₂(CF₃)₃ groups is also appreciably distorted. Temperature‐dependent ¹⁹F NMR studies of the [A₃M₃X]₂ spin system (A = M = CF₃, X = ³¹P) of 5 indicated a rotational barrier ΔG^≠ of 82.3 kJ mol^‐1 at 141 °C. The same Ru₃P₂ core was obtained by the reaction of the unsymmetric diphosphene Mes*‐P=P‐Mes 11 with Ru₃(CO)₁₂; hindered rotation about the C(aryl)—P bonds was also observed, in this case.     

The Crystal Structures of Eu5Ge3 and EuIrGe2

Eu₅Ge₃ and EuIrGe₂ were prepared from the elements in tantalum tubes, and their crystal structures were determined from single crystal X-ray data. Eu₅Ge₃ adopts the structure of Cr₅B₃: I4/mcm, a = 799.0(1)pm, c = 1 536.7(1)pm, Z = 4, wR2 = 0.0421 for 669 F² values and 16 variables. The structure of Eu₅Ge₃ contains isolated germanium atoms and germanium atom pairs with a Ge? Ge distance of 256.0 pm. Eu₅Ge₃ may be described as a Zintl phase with the formulation [5 Eu²⁺]¹⁰⁺[Ge]^4?[Ge₂]^6?. Magnetic investigations of Eu₅Ge₃ show Curie-Weiss behaviour above 50 K with a magnetic moment of μ_exp = 7.6(1) μ_B which is close to the free ion value of μ_eff = 7.94 μ_B for Eu²⁺. EuIrGe₂ is isotypic with CeNiSi₂: Cmcm, a = 445.5(2) pm, b = 1 737.4(4) pm, c = 426.6(1) pm, Z = 4, wR2 = 0.0507 for 295 F² values and 18 variables. The structure of EuIrGe₂ is an intergrowth of ThCr₂Si₂-like slabs with composition EuIr₂Ge₂ and AlB₂-like slabs with composition EuGe₂ in an AB stacking sequence. Both slabs are distorted when compared to the symmetry of the prototypes. The Ge? Ge distance of 256.6 pm in the AlB₂-like fragment is comparable to that in Eu₅Ge₃.     

Drei Alkalimetall‐Erbium‐Thiophosphate: Von der Schichtstruktur bei KEr[P2S7] zur dreidimensionalen Vernetzung in NaEr[P2S6] und Cs3Er5[PS4]6

Three Alkali‐Metal Erbium Thiophosphates: From the Layered Structure of KEr[P₂S₇] to the Three‐Dimensional Cross‐Linkage in NaEr[P₂S₆] and Cs₃Er₅[PS₄]₆ The three alkali‐metal erbium thiophosphates NaEr[P₂S₆], KEr[P₂S₇], and Cs₃Er₅[PS₄] show a small selection of the broad variety of thiophosphate units: from ortho‐thiophosphate [PS₄]^3? and pyro‐thiophosphate [S₃P–S–PS₃]^4? with phosphorus in the oxidation state +V to the [S₃P–PS₃]^3? anion with a phosphorus‐phosphorus bond (d(P–P) = 221 pm) and tetravalent phosphorus. In spite of all differences, a whole string of structural communities can be shown, in particular for coordination and three‐dimensional linkage as well as for the phosphorus‐sulfur distances (d(P–S) = 200 – 213 pm). So all three compounds exhibit eightfold coordinated Er³⁺ cations and comparably high‐coordinated alkali‐metal cations (CN(Na⁺) = 8, CN(K⁺) = 9+1, and CN(Cs⁺) ≈ 10). NaEr[P₂S₆] crystallizes triclinically ( ; a = 685.72(5), b = 707.86(5), c = 910.98(7) pm, α = 87.423(4), β = 87.635(4), γ = 88.157(4)°; Z = 2) in the shape of rods, as well as monoclinic KEr[P₂S₇] (P2₁/c; a = 950.48(7), b = 1223.06(9), c = 894.21(6) pm, β = 90.132(4)°; Z = 4). The crystal structure of Cs₃Er₅[PS₄] can also be described monoclinically (C2/c; a = 1597.74(11), b = 1295.03(9), c = 2065.26(15) pm, β = 103.278(4)°; Z = 4), but it emerges as irregular bricks. All crystals show the common pale pink colour typical for transparent erbium(III) compounds.     

Structure,Chemical Bonding,and Properties of Sc2Ni2In

Sc₂Ni₂In was prepared by a reaction of the elemental components in an are furnace and subsequent annealing at 1070 K. Sc₂Ni₂In is a Pauli paramagnet and a poor metallic conductor with a specific resistivity of 224 mΩcm at room temperature. Its crystal structure was refined from X-ray powder data: P4/mbm, a = 716.79(1) pm, c = 333.154(8) pm, Z = 2, R_wp = 0.040, and R_B(I) = 0.026. Sc₂Ni₂In crystallizes with a ternary ordered version of the U₃Si₂-type structure. The nickel and indium atoms occupy [NiSc₆] trigonal prisms and [InSc₈] square prisms, respectively. These structural fragments are derived from the AlB₂ and CsCl-type structures. Semi-empirical band structure calculations reveal Sc₂Ni₂In to be a nickelide, and the strongest bonding interactions are found for the Sc? Ni contacts, followed by Sc? In and Ni? In. A rigidband model suggests the existence of the isotypic phase Sc₂Ni₂Sb.     

Synthesen und Kristallstrukturen von [Pd9As8(PPh3)8] und [Pd9Sb6(PPh3)8]

Syntheses and Crystal Structures of [Pd₉As₈(PPh₂)₈] and [Pd₉Sb₆(PPh₃)₈] [PdCl₂(PPh₃)₂] reacts with As(SiMe₃)₃ to give the new cluster [Pd₉As₈(PPh₃)₈] ( 4 ). 4 has been characterized by X-ray crystal structure analysis. It is a molecule in which four [Pd₂(PPh₃)₂]-units are bridged by As₂-units. A further Pd atom is located in the centre of the cluster. 4 crystallizes in the space group C2/c with four formula units per unit cell. The lattice constants at 200 K are: a = 3 970.6(3), b = 1 648.90(16), c = 3 266.30(20) pm, β = 131,44(4)°. The reaction of [PdCl₂(PPh₃)₂] with Sb(SiMe₃)₃ yields [Pd₉Sb₆(PPh₃)₈] ( 5 ). 5 consists of a body centred cubic Pd₉-cluster. All of the cube faces are capped by μ₄-Sb-ligands. 5 crystallizes in the space group Pn3 with two formula units per unit cell. The lattice constants at 200 K are: a = b = c = 1 995.4(2) pm.     

Fluoridolyse von Diphosphorylverbindungen

Fluoridolysis of Diphosphoryl Compounds The behaviour of diphosphoryl compounds [X₂(O)P]₂Y in fluoridolysis reactions is decisively determined by the nature of the bridging group Y. In the cases of Y = NH and CH₂ and X = Cl [F₂P(O)]₂N^? and [F₂P(O)]₂CH₂ are obtained quantitatively. For Y = NPh, O, and CH₂ the formation of phosphorylated pentafluorophosphates [F₅P? Y? POX₂]^? is observed. Amido and ester derivatives containing fluorine (see table 2) are obtained from the corresponding chloro compounds by Cl/F exchange. Fluoridolysis of the azadiphosphetidine 19 results in the formation of acyclic 19 a .     

Isolation and Determination of Volatile Organic Compounds from Water by Dynamic Purge-and-Trap Technique Coupled with Capillary Gas Chromatography

The preconcentration technique of purge-and-trap has been investigated in the present work for quantitative adsorption of volatile organic pollutants purged from water samples. A dynamic purging device with variable volume size has been constructed and tested to purge different concentrations of organic compounds. With Tenax GR as the adsorbent, a dynamic purge-and-trap technique was developed combining on-column preconcentration procedures using ambient trapping/thermal desorption/cryogenic focusing/back-flash injection prior to separation and determination using capillary gas chromatography. Various aromatic compounds in water were determined, giving linear working ranges over five orders of magnitude from 0.02 to 5000 µg/L. The analytical procedures were optimized under the assistance of ultrasonication with results validated for the determination of organic contaminants in underground water and tap water, giving over 93% recoveries and a detection limit of 0.01 µg/L, two orders of magnitude lower than those obtained using commercial available instruments with on-line configuration to minimize cross-contamination. The technique provides a potential automated method for in situ monitoring of volatile organic compounds in water.     

Chromium Trioxide Supported onto Wet Silica Gel: Rapid Oxidation of Alcohols to Carbonyl Compounds Under Microwave Irradiation in Solventless System

In an environmentally benign system, alcohols are rapidly oxidized to carbonyl compounds using CrO 3 supported onto wet silica gel as an oxidant under microwave irradiation.     

Synthesis of Bicyclic Compounds Derived from 1,2,4-Benzotriazines

The synthesis of bicyclic compounds derived from benzo[1,2,4]triazines is described.