茂铁基稀土铈配合物的合成与结构

本文利用单羧基二茂铁Fc-COOH和1，1′-二羧基二茂铁HOOC-Fc-COOH作为配体分别合成了双核铈配合物Ce₂(FcCOO)₆ (1)和二维层状配位聚合物Ce₂(OOC-Fc-COO)₃(2)，测定了两种配合物的晶体结构。配合物1中的金属铈离子为九配位结构，分别与周围的羧基二茂铁上的氧原子和作为辅助配体的水分子配位，茂铁间的π-π相互作用将配合物1的二聚体单元连结在一起形成二维的网状结构。配合物2中的金属铈离子亦为九配位结构，分别与周围的羧基二茂铁上的氧原子，作为辅助配体的水分子和甲醇配位形成类似于配合物1的二聚体单元，1，1′-二羧基二茂铁HOOC-Fc-COOH作为桥基配体将二聚体单元连结在一起，形成二维网状的配位聚合物。     

Et2NH2[Nd(S2CNEt2)4]的晶体结构和生成反应焓变

在干燥氮气气氛下,以无水乙醇为溶剂,制备了低水合氯化钕与二乙氨基荒酸二乙铵(D-DDC)配合物,确定其组成为Et2NH2[Nd(S2CNEt2)4].单晶结构分析表明,配合物中4个二乙氨基荒酸根各通过2个硫原子与钕离子成键形成八配位十二面体阴离子,并与二乙铵阳离子形成缔合型分子.晶体属单斜晶系,空间群P21/n,a=1.37517(14)nm,b=2.1146(2)nm,c=1.44641(15)nm,β=102.028(2)°,Z=4.用微量热法测定了298.15K下水合氯化钕和D-DDC在无水乙醇中的溶解焓及二乙氨基荒酸钕液相生成反应焓变分别为(-17.89±0.096),(50.280±0.151)和(-10.116±0.065)kJ/mol,求得固相生成反应焓变.     

Novel Cyanide-Bridged Three-Dimensional Coordination Polymer Derived from an Octahedral Rhenium Cluster [Re6Te8(CN)6]4?: Synthesis and Crystal Structure of [{Mn(H2O)2(DMF)} 2Re6Te8(CN)6]·2H2O

The reaction of a water solution of K₄Re₆Te₈(CN)₆ with a solution of Mn(NO₃)₂ in 0.02M hydrochloric acid in the presence of DMF gave crystals of a cluster rhenium complex [{ Mn(H₂O)₂(DMF)}₂Re₆Te₈(CN)₆]·2H₂O. The structure of the compound was determined by single crystal X-ray diffraction (a = 12.6679(9) Å, b = 17.4524(12) Å, c = 9.7882(6) Å, β = 105.570(6)°, V = 2084.6(3) ų, Z = 2, space group P2₁/n, R = 0. 0389). In the complex, the [Re₆Te₈(CN)₆]⁴⁻ cluster anions are linked to Mn²⁺ cations by the cyanide bridges, the manganese cations being additionally coordinated by the DMF molecule and two water molecules. The neighboring clusters are joined by Re-C-N-Mn bridges into a three-dimensional framework possessing cavities filled with doubly disordered water molecules.Original Russian Text Copyright © 2004 by Yu. V. Mironov, S. F. Solodovnikov, V. E. Fedorov, and Yu. V. Gatilov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 918–922, September–October, 2004.     

The Effect of Vibrational Excitation of Molecules on Plasmachemical Reactions Involving Methane and Nitrogen

An experimental study of plasmachemical reaction involving CH₄ and N₂ molecules in rf discharge was studied in order to know the effect of vibrational excitation of N₂ molecules. When the relative nitrogen concentration was greater than 0.8, the main product of CH₄ decomposition was HCN, and the rate of methane decomposition at this condition was faster than that one in pure methane. These results could be confirmed through the mass spectroscopic method. The reason for these results is the vibrational energy of N₂ excited by rf discharge. The chain reaction mechanisms of producing HCN by vibrational excitation of N₂ were examined closely through numerical simulation. The rate-controlling step was the dissociation reaction of excited nitrogen molecule to the atomic nitrogen, so the process of HCN synthesis was limited by the value of reaction constant, k^N.     

Comparing the Atomic Structures of Binary MO2-SiO2 (M = Ti, Zr or Hf) Xerogels

The incorporation of transition-metal oxides into silica can give materials with useful optical, electronic or catalytic properties. For example, ZrO₂-SiO₂ and HfO₂-SiO₂ materials are of interest due to their high dielectric constants. Here we present a comparison of extended X-ray absorption fine structure and small-angle X-ray scattering results for acid-catalysed binary (MO₂) _x (SiO₂)_{1 – x} (M = Ti, Zr or Hf) xerogels, with x up to 0.4 and heat treatments up to 750°C. Detailed observations for TiO₂-SiO₂ and ZrO₂-SiO₂ xerogels provide a basis for interpretation of new results for HfO₂-SiO₂ xerogels. At low concentrations metal atoms are homogeneously incorporated into the silica network. Ti adopts coordinations of 4 or 6, and Zr and Hf both adopt higher coordination of 6 or 7 (the larger coordinations being due to ambient moisture). At higher concentrations, phase separation of metal oxide occurs. Such regions become clearly separated from the silica network for TiO₂, but remain very finely mixed with silica network for ZrO₂ and HfO₂.     

Polymorphism in mercury(I) selenite(IV): preparation, crystal structures of α-, β-and γ-Hg2SeO3, and thermal behavior of the α- and β-modification

Mercury(I) selenite(IV) is polymorphic and crystallizes at least in three modifications, named α-, β-and γ-Hg₂SeO₃. Polycrystalline β-Hg₂SeO₃ was prepared by precipitation of a concentrated mercurous nitrate solution with selenous acid. Hydrothermal treatment of the colorless β-Hg₂SeO₃ powder in demineralized water at 250°C (10 days) yields light-yellow single crystals of α-Hg₂SeO₃ which show the highest density of the three modifications. Colorless needle-shaped single crystals of β-Hg₂SeO₃ and very few single crystals of γ-Hg₂SeO₃ co-crystallize from strongly diluted Hg₂(NO₃)₂ and H₂SeO₃ solutions and were grown by a diffusion technique. All crystal structures were solved and refined from single crystal diffractometer data sets and are based on Hg₂²⁺ dumbbells and trigonal pyramidal SeO₃²⁻ anions as the main building units. A common structural feature of all modifications is the formation of open channels extending parallel to the shortest crystallographic axis. The non-bonding orbitals of the Se^IV atoms are stereochemically active and protrude into the channels. Upon heating in an open system under N₂ atmosphere, both α- and β-Hg₂SeO₃ decompose in a well-separated three-step mechanism. The first step (T > 250°C) involves disproportionation into elementary mercury and α-HgSeO₃ which at ca. 400°C subsequently transforms into β-HgSeO₃. The second step between T = 400 and 500°C is accompanied by a loss of Hg and SeO₂ and the formation of the basic salt Hg₃SeO₆. In the third step, at temperatures between T = 500° and 600°C, this material decomposes completely. Upon heating in a closed system (sealed silica capillaries), β-Hg₂SeO₃ transforms between 320-340°C into the more dense α-Hg₂SeO₃ which on further heating likewise converts into elementary mercury and β-HgSeO₃.     

Synthesis,thermal stability and structural characterisation of iron(II) phthalocyanine complex with 4-cyanopyridine

A new complex of bis-axially coordinated iron(II) phthalocyanine by 4-cyanopyridine (4-CNpy) has been obtained in crystalline form as an adduct with two 4-CNpy molecules. The [FePc(4-CNpy)₂] · 2(4-CNpy) crystallises in the monoclinic system, space group P2₁/c with two molecules in the unit cell. The iron(II) coordinates four isoindole nitrogen atoms of the almost planar phthalocyaninato(2−) macroring and axially two nitrogen atoms of 4-CNpy molecules. The coordination polyhedron around the Fe(II) atom approximates to a tetragonal by-pyramid. Four equatorial Fe–N bonds are shorter (1.936(2) Å) than two axial Fe–N bonds (2.027(2) Å). The centrosymmetric FePc(4-CNpy)₂ molecules form alternating sheets parallel to the bc crystallographic plane and solvated 4-CNpy molecules that are anti-parallel oriented by their polar cyano groups are located between the sheets of FePc(4-CNpy)₂ molecules. Ligation of the intermediate-spin iron(II) phthalocyanine by 4-CNpy molecules leads to the low spin Fe(II) complex. The importance of the d(π) → π^∗(Pc) back donation is manifested in the difference between the values of C–N isoindole and C–N azamethine bond lengths of the Pc macrocycle. The thermal analysis of the crystals of [FePc(4-CN)₂] · 2(4-CNpy) shows two steps responsible for a loss of solvated (∼170 °C) and coordinated (∼235 °C) 4-CNpy molecules.     

The Sialons MLn[Si4−xAlxOxN7−x] with M = Eu,Sr, Ba and Ln = Ho‐Yb – Twelve Substitution Variants with the MYb[Si4N7] Structure Type

The oxonitridoalumosilicates (so‐called sialons) MLn[Si_4?xAl_xO_xN_7?x] with M = Eu, Sr, Ba and Ln =Ho, Er, Tm, Yb were obtained by the reaction of the respective lanthanoid metal, the alkaline earth carbonates or europium carbonate, resp., AlN, “Si(NH)₂” and MCl₂ as a flux in a radiofrequency furnace at temperatures around 2100 °C. The compounds MLn[Si_4?xAl_xO_xN_7?x] are relevant for the investigation of substitutional effects on the materials properties due to their ability of tolerating a comparatively large phase width up to x ≈ 2.0(5). The crystal structures of the twelve compounds were refined from X‐ray single crystal data and X‐ray powder data and are found to be isotypic to the MYb[Si₄N₇] structure type. The compounds crystallize in space group P6₃mc (no. 186, hexagonal) and are made up of chains of so‐called starlike units [N^[4](SiN₃)₄] or [N^[4]((Si,Al)(O,N)₃)₄], respectively. These units are formed by four (Si,Al)(N/O)₄ tetrahedra sharing a common central nitrogen atom. The structure refinement was performed utilizing an O/N‐distribution model according to Paulings rules, i.e. nitrogen was positioned on the four‐fold bridging site and nitrogen and oxygen were distributed equally on both of the two‐fold bridging sites, resulting in charge neutrality of the compound. The Si and Al atoms were distributed equally on their two crystallographic sites, referring to their elemental proportion in the compound, due to being poorly distinguishable by X‐ray methods. The chemical compositions of the compounds were derived from electron probe micro analyses (EPMA).     

新的含有4-对甲基苯基-3，5-二(2-吡啶基)-1，2，4-三氮唑钴配合物的合成和晶体结构(英)

A new cobalt(Ⅱ) complex, [CoL₂(NCS)₂]·2CH₂Cl₂, [L=4-(p-methylphenyl)-3,5-bis(pyridin-2-yl)-1,2,4-triazole], was synthesized and its crystal structure was determined by X-ray analysis. The complex crystallizes in monoclinic system with space group P2₁/c, a=0.867 40(17), b=1.453 9(3), c=1.781 9(4) nm, β=91.18(3)°, V=2.246 7(8) nm³ and Z=2. The cobalt atom is in a distorted octahedral environment with two bidentate chelating L ligands in the equatorial plane and two NCS^- ions in the axial positions. CCDC: 251658.     

Mixed-metal cluster chemistry. 26 . Proclivity for “all-terminal” or “plane-of-bridging-carbonyls” ligand disposition in tungsten-triiridium clusters

Reaction of WH(CO)₃(η-C₅Me₅) with IrCl(CO)₂(4-H₂NC₆H₄Me) affords WIr₃(μ-CO)₃(CO)₈(η-C₅Me₅) in low yield. A structural study reveals a WIr₂-centred plane of bridging carbonyls, in contrast to the crystal structure of WIr₃(CO)₁₁(η-C₅H₅) (all-terminal carbonyl distribution). DFT calculations reveal an increasing proclivity to adopt an all-terminal CO disposition for clusters MIr₃(CO)₁₁(η-C₅H₅) in the gas phase on proceeding from M=Cr to Mo and then W, consistent with structural studies in the solid state for which the tungsten-containing cluster is the only all-terminal example. Increasing electron donation from the ligands in the tungsten system (either from phosphine substitution or cyclopentadienyl permethylation) suffices to impose a plane of bridging carbonyls in the ground state structure. ¹³C NMR fluxionality studies reveal that CO exchange mechanism(s) for WIr₃(CO)₁₁(η-C₅H₅) and the related tetrahedral cluster W₂Ir₂(CO)₁₀(η-C₅H₅)₂ are very fast and involve all carbonyls on the clusters. DFT calculations on MIr₃(CO)₁₁(η-C₅H₅) (M=Cr, Mo) substantiate a ‘merry-go-round’ mechanism for carbonyl scrambling in these systems, a result which is consistent with the scrambling behaviour seen in the NMR fluxionality studies on the W-containing congener.