Carbon-carbon coupling on tetrahedral iridium clusters: X-ray molecular structures and multinuclear NMR studies of the two isomeric forms of [Ir4(CO)6(μ3-η-HCCPh)(μ2-η-C4H2Ph2)(μ-PPh2)2]

The reactions of [HIr₄(CO)₉(Ph₂PCCPh)(μ-PPh₂)] (1) or [Ir₄(CO)₈(μ₃-η²-HCCPh)(μ-PPh₂)₂] (2) with HCCPh gave two isomeric forms of [Ir₄(CO)₆(μ₃-η²-HCCPh)(μ₂-η⁴-C₄H₂Ph₂)(μ-PPh₂)₂] (3 and 4) in good yields as the only products. These compounds were characterized with analytical and spectroscopic data including ¹H, ¹³C and ³¹P NMR (1 and 2D) spectroscopy and their molecular structures were established by X-ray diffraction studies. Compounds 3 and 4 exhibit the same distorted butterfly metal polyhedral arrangement of metal atoms with two μ-PPh₂ that occupy different positions in the structures of the two isomers. Both molecules contain a HCCPh ligand bonded in a μ₃-η²-// mode to one of the wings of the butterfly and a metallacyclic ring, which resulted from head-to-tail coupling, in the case of [Ir₄(CO)₆(μ₃-η²-HCCPh){μ₂-η⁴-(H)CC(Ph)C(H)C(Ph)}(μ-PPh₂)₂] (3) and tail-to-tail coupling, in that of [Ir₄(CO)₆(μ₃-η²-HCCPh){μ₂-η⁴-(H)CC(Ph)C(Ph)C(H)}(μ-PPh₂)₂] (4), and which is linked to two metal atoms of the second wing of the butterfly.     

Syntheses, Structures, and Nonlinear Optical Properties of Two Crown-like Heteroselenometallic Compounds [Et4N]4[(μ5-WSe4)(CuX)5(μ-X)2] (X = Cl, Br)

Two isostructural crown-like heteroselenometallic cluster compounds, [Et₄N]₄[(μ₅-WSe₄)(CuX)₅(μ-X)₂] (X = Cl 1, Br 2), were prepared from the reactions of [Et₄N]₂[WSe₄] with CuX and [Et₄N]X· xH₂O in the presence of 2-picoline and characterized by single-crystal diffraction analysis. The [(μ₅-WSe₄)(Cu-X)₅(μ-X)₂]⁴⁻ anions in the cluster compounds consists of five CuX fragments coordinated to the five edges of the tetrahedral [WSe₄]²⁻ moiety along with two bridging halides connected to each of the two pairs of the symmetric copper atoms, exhibiting a novel crown-like core structure. The nonlinear optical absorption and refraction of cluster compound 2 were determined to be α₂ = 6.15 × 10⁻¹⁰ m/W and n ₂ = 4.18 × 10⁻¹¹ esu, respectively.     

Preparation and reactivity of metal-containing monomers

The thermal decomposition of iron (III) acrylate, [Fe₃O(CH₂=CHCOO)₆ · 3H₂O]OH (FeAcr), a monomer with a complex cluster cation, has been studied at 200–370 °C. Thermal transformations of FeAcr occur in two temperature regions. The rates of gas evolution in the low temperature region (200–300 °C) and the high temperature region (300–370 °C) are described by first-order equations withk=4.2 · 10²¹exp[−59000/(RT)] s⁻¹ andk=1.3 · 10⁶exp[−30500/(RT)] s⁻¹, respectively. A study of the qualitative and quantitative composition of the products of FeAcr thermolysis was carried out. The thermal transformation of FeAcr is a complex process of dehydration, degradation, and polymerization in the solid phase followed by decarboxylation of the metal-carboxyl groups of the polymer. for part 33 see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1743–1750, October, 1993.     

CnB-的激光等离子体产生与质谱分析

Time-of-flight mass spectrum of C_nB~- has been recorded on a selfbuilt instrument with laser vaporization of tetraphenylboron sodium. By analysis of the com-position of the anions, it is found that number of the boron atoms in any of these ions equals to the number of the charges carried by the anion, and the sum of the numbers of the carbon and boron atoms in these species are always the odd numbers. The experimental results show that boron atom has a strong tendency to attract an electron so that those C_nB~- will have similar electronic structures as C_n, and carbon clusters with odd members are always more stable than their even neighbors.     

Theoretical Study of Ethanethiol Adsorption on HZSM-5 Zeolite

The density functional theory and the cluster model methods have been employed to investigate the interactions between ethanethiol and HZSM-5 zeolites. Molecular complexes formed by the adsorption of ethanethiol on silanol H3SiOH with two coordination forms, model Bronsted acid sites of zeolite cluster H3Si(OH)Al(OH)2SiH3 interaction with ethanethiol, aluminum species adsorbed ethanethiol have been comparatively studied. Full optimization and frequency analysis of all cluster models have been carried out using B3LYP hybrid method at 3-21G basis level for hydrogen atoms and 6-31G(d) basis set level for silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms of H3Si(OH)Al(OH)2SiH3-ethanethiol, silanol-ethanethiol and Al(OH)3-ethanethiol have been studied. The calculated results showed the nature of interactions was van der Waals force as exhibited by not much change in geometric structures and properties. The preference order of ethanethiol adsorbed on HZSM-5 zeolite may be residual aluminum species, bridging hydroxyl groups and silanol OH groups from the adsorption heat. The adsorbed models of protonized ethanethiol on bridging hydroxyl OH groups and linear hydrogen bonded ethanethiol on bridging OH groups suggested in literature might not exist as revealed by this theoretical calculation. Possible adsorption models were obtained for the first time.     

Growth of clusters in a first-order phase transition

The results of computer simulations of phase separation kinetics in a binary alloy quenched from a high temperature are analyzed in detail, using the ideas of Lifshitz and Slyozov. The alloy was modeled by a three-dimensional Ising model with Kawasaki dynamics. The temperature after quenching was 0.59T _c, whereT _c is the critical temperature, and the concentration of minority atoms was=0.075, which is about five times their largest possible single-phase equilibrium concentration at that temperature. The time interval covered by our analysis goes from about 1000 to 6000 attempted interchanges per site. The size distribution of small clusters of minority atoms is fitted approximately byc ₁(1-)³ w(t),c ₁ (1–)⁴ Q _l w(t)^l(2l10); wherec _l is the concentration of clusters of sizel;Q ₂,...,Q ₁₀ are known constants, the cluster partition functions;t is the time; andw(t)=0.015(1+7.17t ^–1/3). The distribution of large clusters (l20) is fitted approximately by the type of distribution proposed by Lifshitz and Slyozov,c _l ,(t)=–(d/dl) [lnt+p (l/t)], where is a function given by those authors and is defined by(x)=C _o e–x-C ₁ e ^–4x/3-C ₂ e ^–5x/3;C ₀,C ₁,C ₂ are constants determined by considering how the total number of particles in large clusters changes with time.Supported by the U.S. Air Force Office of Scientific Research under Grant No. 78-3522 and by the U.S. Department of Energy under Contract No. EY-76-C-02-3077*000.     

氟化钾团簇的相变、成核和重结晶的分子动力学模拟

我们利用Born-Mayer-Huggins相互作用势函数对(KF)_N(N=108，256，500和864)团簇进行了分子动力学(MD)模拟。为了避免周期性边界条件对相变、成核和重结晶的干扰作用，对体系采用了自由边界。基于MD模拟结果，对团簇的熔化温度、熔化焓、扩散系数、成核速率、固液界面自由能、临界核大小等进行了计算和讨论。在对(KF)₈₆₄双晶团簇的热退火模拟中，观察到了固态的重结晶和晶粒的生长。经典的成核理论成功地解释了(KF)₈₆₄双晶团簇的重结晶MD模拟结果。     

Darstellung, 19F-NMR-spektroskopischer Nachweis und Untersuchung zur Bildung der metallgemischten Clusteranionen [(Mo6−nWnCl)F]2−, n = 0−6

Preparation, ¹⁹F NMR Spectroscopic Evidence and Study of the Formation of Metal-Mixed Cluster Anions [(Mo_6?nW_nCl )F ]^2?, n = 0?6 The complete system of metal-mixed octahedral cluster ions [(Mo_6?nW_nCl)F]^2?, n = 0?6, is prepared by tempering Mo powder with WCl₆ at 600°C. A mixture containing inclusively the geometric isomers (n = 2, 3, 4) all ten possible species is transferred into the tetra-n-butylammonium salts (TBA)₂[(Mo_6?nW_nCl)F]. In the ¹⁹F nmr spectrum the 24 expected signals are observed, assigned on the basis of their chemical shifts, multiplicities and intensities, and confirmed by a 2D-¹⁹F-¹⁹F COSY spectrum. From the integrated intensities the distribution of the different components is derived revealing a non-statistical formation, in that isomers with Mo…?Mo or W…?W atoms in trans-positions in comparision to those with mixed Mo…?W axes are favoured, and that especially the homoleptic compounds Mo₆ and W₆ are present to an over-average extent. Evaluation of ¹⁹F chemical shifts reveals that F bound to W which is in antipodal position to Mo resonates at higher field compared to F bound to W in a W…?W arrangement, caused by an increased shielding, which is synonymous to a positive antipodal-effect by Mo. Vice versa F bound to Mo with an antipodal W resonates at lower field compared with F bound to Mo in an Mo…?Mo arrangement caused by an increased deshielding and synonymous a negative antipodal-effect by W. The chemical shifts, resulting from antipodal-effects, are different for the compounds within the [(Mo_6?nW_nCl)F]^2? - system. The difference of the antipodal effect of successive substitution products results in characteristic values designated as antipodal shift constants, depending on the kind of substituents, which is valid for other cluster systems, too.     

Synthesis and Structure of the Centered Cluster Compound Ba3(Zr6Cl18Be)

Reaction of powdered Zr with ZrCl₄, BaCl₂ and Be in suitable proportions in a Ta container at 800°C produces the title compound. Suitable monocrystals for X-ray diffraction were obtained from reactions to which a comparable amount of Hg₂Cl₂ had been added. The structure of Ba₃Zr₆Cl₁₈Be is a superstructure of the K₂ZrCl₆ · Zr₆Cl₁₈H type (R3 c, Z = 6; a = 9.6852 (9) Å, c = 52.52 (1) Å; R, R_w = 2.7, 3.2% for 826 independent reflections, 2θ ≤ 50°). Trigonally compressed [Zr₆(Be)Cl₁₂ⁱ]Cl₆^a clusters are interconnected by six-coordinate barium atoms that lie in Cl^a antiprisms (a twisted version of the Zr^IV site) while (9 + 3)-coordinate barium substitutes for potassium within chlorine layers. Distortions associated with the size and field of barium are responsible for the superstructure and for differences from other analogues.     

离子簇合物HeN_2~+的电子光谱的从头算研究

本文报道了离子簇合物HeN2＋的电子光谱的从头算结果。在MCSCF／6－31G（d，p）水平上，对其基态进行了几何优化，用该构型．在SDC1／6－31（d，p）水平上计算了基态的总能量。用SDCI方法计算得到HeN2＋从基态到选择激发态的垂直跃迁能、振子强度、跃迁频率、辐射寿命以及Einstain系数。该结果可以较好的验证maier的实验。