Vibrational spectroscope of complexes of platinum(0)—I. Tetrakis(triphenylphosphine)platinum(0) and Dioxygenbis(triphenylphosphine)platinum(0)

Assignment of i.r. and Raman spectra for Pt(PPh₃)₄ and Pt(O₂)(PPh₃)₂ yielded values for νPtP of 137 and 157 cm⁻¹ (Pt(PPh₃)₄); 132 (antisymmetric) and 145 cm⁻¹ (symmetric) (Pt(O₂)(PPh₃)₂). For the dioxygen complex, solution phase Raman spectra gave values for both ν PtO₂ modes for the first time. Data from the ¹⁶O₂, ¹⁶O¹⁸O and ¹⁸O₂ isotopomers were used in a normal coordinate analysis of the PtO₂ fragment. The OO stretching force constant (3.0 mdyn Å⁻¹) is consistent with extensive net π-back-donation into the π* m.o.s of the O₂ ligand.     

Insertionen in Wolfram(0)Kohlenstoff- und Wolfram(0)Wasserstoff-Bindungen

Trans-dicarbonylmethylnitrosyl-bis(triisopropylphosphite)tungsten (1) reacts with CO or CO₂ to give (CO)₂(ON)[P(O-i-Pr)₃]₂WCOCH₃ (2) or (OC)(ON)[P(O-i-Pr)₃]₂W-η²-OOCCH₃ (3), respectively.The hydride complex (OC)₂(ON)[P(O-i-Pr)₃]₂WH (4a) undergoes insertion by CO₂ or by activated acetylenes such as propiolic aldehyde or methyl propiolate to give (OC)₂(ON)[P(O-i-Pr)₃]₂OC(O)H (5) or (OC)₂(ON)]P(O-i-Pr)₃]₂CHCHR (R  CHO, 6; R  COOCH₃, 7). 4a adds BH₃ to yield a (OC)₂(ON)[P(O-i-Pr)₃]₂WHBH₃ system 8. This in turn can react with CO to give 4a and a (OC)₃(ON)P(O-i-Pr)₃WH complex (4b).     

Ag adsorption on Cd-terminated CdS (0 0 0 1) and S-terminated CdS (0 0 0 1?) surfaces: First-principles investigations

First-principles calculations are performed to study the adsorption of Ag at Cd-terminated CdS (0 0 0 1) and S-terminated CdS (0 0 0 1?) surfaces as a function of Ag coverage. Our results reveal that Ag adsorption at Cd-terminated (0 0 0 1) has a large binging energy than at S-terminated (0 0 0 1?) surface. For Ag adsorption at Cd-terminated (0 0 0 1) surface, T4 structure is more favorable and the Ag-Cd bond posses an ionic-like character. While for Ag adsorption at S-terminated (0 0 0 1?) surface, the H3 structure is most stable and the bonding between Ag-S is covalent. It is found that the magnitude and the sign of surface dipole moment are partly determined by the difference between the electronegativities of Ag and the host atom bonding with Ag. The adsorption energy changes as a function of Ag coverage. In addition, related properties of Ag cluster adsorption at Cd-terminated (0 0 0 1) surface are also discussed.     

《色谱》第 2 0卷 (2 0 0 2年 )总目次

研究报告胰蛋白酶水解全酪蛋白反应过程中的色谱分析齐　崴 ,何明霞 ,何志敏 ,史德青 (1)……………………………………………多氯代二苯并呋喃的结构信息连接性指数与其在不同色谱柱上的气相色谱保留行为的关系余训民 ,杭义萍 (6 )……………苯乙烯 氧乙烯 苯乙烯三嵌段聚合物的受限结晶行为的反气相色谱分析陈胜洲 ,邹其超 ,张金枝 (12 )…………………………遗传算法用于液相色谱分离条件的优化陈学国 ,倪坚毅 ,邹汉法 ,赵瑞环 (97)……………………………………………………种子溶胀悬浮聚合法制备分子印迹聚合物微球成国祥 ,张立永 ,付…     

Variation of radiative lifetimes of NH2(Ã2A1) with rotational levels in the (0, 8, 0) and (0, 9, 0) vibration bands

Radiative lifetimes from the first electronically excited state of the amidogen free radical, NH(2)(A?(2)A(1)), are reported for rotational states in selected vibrational levels ν(2)' using laser-induced fluorescence. Thermal collision of argon, Ar(?)((3)P(0), (3)P(2)) metastable atoms in a microwave discharge-flow system with ammonia (NH(3)) molecules produced ground state NH(2)(X?(2)B(1)). The radiative lifetimes for the deactivation of NH(2)(A?(2)A(1)) were determined by measuring the decay profiles of NH(2)(A?(2)A(1)?→?X?(2)B(1)). In addition to the Fermi resonances with the ground state that lengthen the radiative lifetimes, a systematic increase in the radiative lifetimes with rotational quantum number was observed. Furthermore, the average radiative lifetimes of the (0, 9, 0) Γ, τ(1) = 18.65 ± 0.47 μs and (0, 8, 0) Φ, τ(2) = 23.72 ± 0.65 μs levels were much longer than those of the (0, 9, 0) Σ, τ(3) = 10.62 ± 0.47 μs, and (0, 8, 0) Π, τ(4) = 13.55 ± 0.55 μs states suggesting increased mixing of the first electronic excited and the ground states.     

Synthesis of Two Isomeric Tetrasaccharides 0-α-L-Fucopyranosyl-(1→3) and (1→4)-0-(2-Acetamido-2-Deoxy-β-D-Glucopyranosyl)-(1→3)-0-(β-D-Galactopyranosyl)-(1→4)-D-Glucopyranose and a Related Tetrasaccharide 0-α-L-Fucopyranosyl-(1→3)-0-(2-Acetamido-2-Deoxy-β-D-Glucopyranosyl-(1→6)-0-(β-D-Galactopyranosyl)-(1→4)-D-Glucopyranose

ABSTRACT

Synthesis of three tetrasaccharides, namely, 0-α-L-fucopyranosyl-(1→3)-0-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→3)-0-(β-D-galactopyranosyl)-(1→4)-β-D-glucopyranose (7), 0-α-L-fucopyranosyl-(1→4)-0-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→3)-0-(β-D-galactopyranosyl)-(1→4)-D-glucopyranose (9), and 0-α-L-fucopyransoyl-(1→3)-0-(2-acetamido-2-deoxy-β-D-glucopyransoyl)-(1→6)-0-(β-D-galactopyranosyl)-(1→4)-D-glucopyranose (15) has been described. Their structures have been established by ¹³C NMR spectroscopy.     

(η6-Anisole) (η2-benzene) dicarbonylchromium(0): an intermediate in the photochemical carbonyl substitution of (η6-anisole)tricarbonylchromium(0) in benzene

The photochemical carbonyl substitution of (η⁶-anisole)Cr(CO)₃ has been investigated by laser flash photolysis. Both transient spectra and second-order rate constants for the reactions of transients with nucleophiles are found to be extremely variable depending upon solvents used. The coordination of benzene to the transient in cyclohexane forms the transient in benzene, indicating two discrete chemical species: (η⁶-anisole)Cr(CO)₂ and (η⁶-anisole)Cr(CO)₂(η²-benzene). The latter type of transient was observed also for fluorobenzene and mesitylene, leading to the assignment of a weak band in the visible region as η²-arene → Cr charge transfer. The existence of (η⁶-arene)Cr(CO)₂(η²-arene′) may throw light on what have been described as solvent effects in organometallic reactions.     

Pu(7Fg)＋CO(X 1Σ＋，0，0)的分子反应动力学

基于PuCO分子基态()的分析势能函数， 用准经典的Monte Carlo轨线法对Pu(7Fg)＋CO(0，0)的分 子反应动力学过程进行了计算.结果表明, Pu(7Fg)与CO(0，0)碰撞易生成PuCO络合物分子，该反应是无阈能反应，反应截面σ随能量Et的升高而下降，当Et=502.1 kJ•mol－1时，σ几乎为零.     

Semiclassical glory analyses in the time domain for the H + D2(v(i) = 0, j(i) = 0) → HD(v(f) = 3, j(f) = 0) + D reaction

We make the first application of semiclassical (SC) techniques to the plane-wavepacket formulation of time-domain (T-domain) scattering. The angular scattering of the state-to-state reaction, H + D(2)(v(i) = 0, j(i) = 0) → HD(v(f) = 3, j(f) = 0) + D, is analysed, where v and j are vibrational and rotational quantum numbers, respectively. It is proved that the forward-angle scattering in the T-domain, which arises from a delayed mechanism, is an example of a glory. The SC techniques used in the T-domain are: An integral transitional approximation, a semiclassical transitional approximation, a uniform semiclassical approximation (USA), a primitive semiclassical approximation and a classical semiclassical approximation. Nearside-farside (NF) scattering theory is also employed, both partial wave and SC, since a NF analysis provides valuable insights into oscillatory structures present in the full scattering pattern. In addition, we incorporate techniques into the SC theory called "one linear fit" and "two linear fits", which allow the derivative of the quantum deflection function, Θ?(')(J), to be estimated when Θ?J exhibits undulations as a function of J, the total angular momentum variable. The input to our SC analyses is numerical scattering (S) matrix data, calculated from accurate quantum collisional calculations for the Boothroyd-Keogh-Martin-Peterson potential energy surface No. 2, in the energy domain (E-domain), from which accurate S matrix elements in the T-domain are generated. In the E-domain, we introduce a new technique, called "T-to-E domain SC analysis." It half-Fourier transforms the E-domain accurate quantum scattering amplitude to the T-domain, where we carry out a SC analysis; this is followed by an inverse half-Fourier transform of the T-domain SC scattering amplitude back to the E-domain. We demonstrate that T-to-E USA differential cross sections (DCSs) agree well with exact quantum DCSs at forward angles, for energies where a direct USA analysis in the E-domain fails.     

Theoretical analysis of initial adsorption of high-κ metal oxides on In(x)Ga(1-x)As(0 0 1)-(4×2) surfaces

Ordered, low coverage to monolayer, high-κ oxide adsorption on group III rich InAs(0 0 1)-(4×2) and In(0.53)Ga(0.47)As(0 0 1)-(4×2) was modeled via density functional theory (DFT). Initial adsorption of HfO(2) and ZrO(2) was found to remove dangling bonds on the clean surface. At full monolayer coverage, the oxide-semiconductor bonds restore the substrate surface atoms to a more bulklike bonding structure via covalent bonding, with the potential for an unpinned interface. DFT models of ordered HfO(2)/In(0.53)Ga(0.47)As(0 0 1)-(4×2) show it fully unpins the Fermi level.     

星际尘埃HC_(3-x)NC_x(x=0～3)与HC_(5-x)NC_x(x=0～5)分子的DFT研究

运用密度泛函理论（DFT）中的B3LYP方法,计算了星际尘埃HC_3N,HC_5N分子 及它们的同分异构体的分子结构、相对稳定性、偶极矩、转动常数等,对于HC_(3- x)NC_x(x = 0～3),HC_3N分子比其它的异构体要稳定,将计算所得的HC_3N, HC_2NC的转动常数B_0与实际的观测值B_0相比较,发现两者能较好地吻合。比较 HC_(5-x)NC_x(x = 0～5)的各同分异构体的总能量,发现HC_5N的相对稳定性最高 ,但它的偶极矩相对较低。将HC_5N的转动常数B_0的理论计算值与实际观测值进行 比较,其相对标准误差仅0.6%。     

X-ray structure of (N-heterocyclic)(η4-diene)-dicarbonyliron(0) compounds

(N-Heterocyclic)(η⁴-diene)dicarbonyliron(0) compounds, where the N-heterocycles are quinoline and pyrazine and the diene is the diethyl ester of the hexa-2,4-dien-1,6-dioic acid (diethyl muconate) were studied by X-ray diffraction. The measurements demonstrated that the N-heterocycle occupies different positions of a tetragonal pyramid in these compounds. Quinoline occupies a basal position and pyrazine an apical position. This is discussed in terms of the π-bonding ability of the ligands.     

含膦配体的羰基钼(0)和钨(0)化合物的改进合成，反应及催化活性

MoCl_5或WCl_6与锌粉及适当的膦配体和CO在常压常温进行反应,合成了含膦配体的羰基钼和钨的化合物(Ph_2PR)_nM(CO)_(6-n)(M=Mo,W;R=Me,Et,n-Pr,Ph;n=2,3)。用该方法也成功地将M(CO)_5(M=Mo,W)单元负载到含膦的高分子链上,化合物(Ph_2PEt)_2Mo(CO)_4与HgCl_2反应得到含Mo-Hg键的化合物。用(Ph_3P)_2Mo(CO)_4和(Ph_3P)_2Ni(CO)_2二元催化体系,在适当温度和压力下对甲醇羰基化反应进行了初步研究,得到了醋酸和醋酸甲酯。该催化过程对甲醇的转化率可达92％,对醋酸和醋酸甲酯的选择性可达68％。     

MOLECULAR AND CRYSTAL STRUCTURE OF (η~6-BENZOPHENONE)TRICARBONYLCHROMIUM(0)

<正> The crystal of (η6-C6H5C(O)C6H5)Cr(CO)3 belongs to monoclinic system with space group P21/n. The cell parameters are: a=ll.068(2), b= 7.501(2), c=17.174(2) A, β=91.22(2)0, V=1425.4(8) A3, Z=4. The structure was solved by the analysis of 1745 observed reflections recorded on CAD-4 diffractometer. The final R=0.053.     

富勒烯(C~6~0, C~7~0)的金属有机化学

综述了1990年以来富勒烯金属有机化学研究的进展,结果表明富勒烯(C~6~0,C~7~0)能与第VIII及IVB、VB、VIB、VIIB族等过渡金属形成各类衍生物,具有潜在的应用前景。     

Theoretical insight into stereodynamics of the O(D) + H2 (v = 0–3, j = 0) → OH + H reaction: A quasiclassical trajectory (QCT) study

In this work, the reaction O(¹D) + H₂ → OH + H has been theoretically studied using the quasiclassical trajectory (QCT) method developed by Han and co-workers. All the quasiclassical trajectory calculations are performed on the DK (Dobbyn and Knowles) potential energy surface (PES). The vector correlation information on the reaction O(¹D) + H₂ → OH + H has been obtained. It has been demonstrated that the product alignment is sensitive to the reactant vibrational quantum number (v) at collision energy of 19 kcal/mol. Moreover, with increasing the value of v, backward scattering becomes weaker and forward scattering becomes stronger.     

1.9分辨率(D-Ala)~(B_0)猪胰岛素晶体结构的研究

本文应用差值Fourier技术和制约立体化学参数最小二乘技术以二锌猪胰岛素模型为起点测定了1.9分辨率的(D-Ala)~(B0)猪胰岛素晶体结构,R因子为0.211,键长均方差为0.057。B_0残基的电子密度表现清晰。B_0的引入降低了B链N端肽段构象的运动性,使分子在晶体中的堆积更加紧密。(D-Ala)~(B0)猪胰岛素和二锌猪胰岛素结构的主要差异在于分子可能的受体结合表面中部分极性基团的构象和分子IA链两段螺旋的组装。(D-Ala)~(B0)猪胰岛素B链N端晶体学微环境与(Trp)~(B1)猪胰岛素和去B_1牛胰岛素有很大的差异。本文还简单地讨论了胰岛素分子结构与免疫功能的关系。     

Reduktive CC-kupplung von zwei isocyanid-liganden an Mo(II)- und W(II)-zentren,eine reaktionssequenz über isocyanid- und aminocarbin-komplexe von Mo(0) und W(0)

The octahedral alkylisocyanide complexes M(RNC)₆ and alkylisocyanide-substituted aminocarbyne complexes [(RNC)₅MCN(Et)R]BF₄ (M = Mo, W; R = Et, ^tBu) have been found to be key intermediates in the reductive coupling of two isocyanide ligands to a complexed alkyne. The crucial step in the reaction sequence leading from the seven-coordinate starting materials [M(RNC)₆Br]Br to the bis(amino)acetylene products [I(RNC)₄M[η²-R(Et)NCCN(H)R]]BF₄ and [I(RNC)₄M[η²-R(H)NCCN(H)R]]I involves an aminocarbyne-isocyanide coupling reaction induced by HI. The composition and structure of the intermediates and the products have been fully characterized.     

Angular scattering using parameterized S matrix elements for the H + D2(v(i) = 0, j(i) = 0) → HD(v(f) = 3, j(f) = 0) + D reaction: an example of Heisenberg's S matrix programme

A neglected topic in the theory of reactive scattering is the use of parameterized scattering (S) matrix elements to calculate differential cross sections (DCSs). We construct four simple parameterizations, whose moduli are smooth step-functions and whose phases are quadratic functions of the total angular momentum quantum number. Application is made to forward glory scattering in the DCS of the H + D(2)(v(i) = 0, j(i) = 0) → HD(v(f) = 3, j(f) = 0) + D reaction at a translational energy of 1.81 eV, where v and j are vibrational and rotational quantum numbers respectively. The parameterized S matrix elements can reproduce the forward scattering for centre-of-mass reactive scattering angles up to 30° and can identify the total angular momenta (equivalently, impact parameters) that contribute to the glory. The theoretical techniques employed to analyze structure in the DCS include: nearside-farside theory, local angular momentum theory--in both cases incorporating resummations of the partial wave series representation of the scattering amplitude--and the uniform semiclassical theory of forward glory scattering. Our approach is an example of Heisenberg's S matrix programme, in which no potential energy surface is used. Our calculations for the DCS using the four parameterized S matrix elements are counterexamples to the following universal statements often found in the chemical physics literature: "every molecular scattering investigation needs detailed information about the interaction potential," and "an accurate potential energy surface is an essential element in carrying out simulations of a chemical reaction". Both these statements are false.