（RCp）2TiCl2—Pr^iMgBr存在下二苯乙炔的选择性加氢

最近我们发现了在催化量(RCp)_2TjCl_2-Pr~iMgBr存在和常温常压下二苯乙炔的加氢反应。该反应以H_2为还原剂,经顺、反式二苯乙烯可定量地得到二苯乙烷。它比以格氏试剂为还原剂的钛氢化反应更具优越性。     

双核钛氢络合物在二苯乙炔加氢反应中的催化作用

我们曾研究了Cp_2~′TiCl_2-Pr~iMgBr体系存在下,二苯乙炔的催化加氢反应,为了探讨催化剂结构对反应的影响,本文考察了几种双核钛络合物的催化活性,发现它们能对炔烃的加氢起催化作用,随络合物分子中2个钛原子的靠近,其加氢催化活性明显减小。     

二茂二氯化钛存在下炔烃的还原反应

研究了双取代乙炔在二茂二氯化钛存在下被异丁基溴化镁格氏试剂还原生成烯烃的过程. 结果表明, 二苯乙炔还原后几乎得到专一的Z-二苯乙烯, 但多数炔烃还原后主要产物为E式烯烃, Z,E异构体的比例与底物炔烃的性质及位阻有关. 本文还报导了以双取代乙炔为底物, 径钛氢化反应合成了9组烯烃异构体混合物, 并对其结构进行了分析鉴定.     

钛氢化反应中的电子效应

近年来,有机钛化学是一个十分引人注目的领域,钛氢化反应在有机合成中的应用越来越广泛。钛氢试剂对不饱和有机化合物,诸如烯烃、炔烃、羰基化合物、腈等有着良好的还原作用,同时也是烯烃异构化的有效的催化剂。但是钛氢化反应的电子效应尚未见系统的论述。本文从电子效应的角度,运用硬软酸碱理     

HB（C6F5）2催化的非官能团化的烯烃的氢化反应

烯烃的催化氢化为烯烃向烷烃的转化提供了最具有原子经济性的途径.目前,用于烯烃氢化的催化剂主要为过渡金属化合物,而开发低毒高效的非金属烯烃氢化催化剂正在吸引越来越多的关注.其中非官能团化的烯烃的非金属催化氢化,是一项非常具有挑战性的课题.复旦大学化学系王华冬课题组发现以具有强Lewis酸性的硼氢化合物HB(C6F5)2为催化剂,可以成功地实现一系列非官能团化的烯烃的催化氢化反应.动力学实验及密度     

锆、钛介导的烯烃、炔烃硼氢化（英文）

过渡金属催化的烯烃、炔烃硼氢化反应是制备硼酸酯类化合物最为有效的方法之一,该反应具有100%的原子经济性,原料简单易得,产物多样性可调等优点.已知的金属催化剂大都依赖于铑、铱、钯、铂、钴、铁、铜等后过渡金属,而使用前过渡金属锆、钛作为催化剂的反应体系则鲜有报道.总结了锆、钛介导的(化学计量与催化量)烯烃、炔烃硼氢化反应的研究现状,并对今后锆、钛催化的烯烃、炔烃硼氢化反应的发展进行了展望.     

密度泛函理论计算研究表面应力对钯催化乙炔选择性加氢活性与选择性的影响（英文）

在石油催化裂解过程中,除了生成乙烯、丙烯及丁烯等烯烃,还会产生部分炔烃.目前工业上通常采用炔烃选择性加氢转化为对应的单烯烃,以除去其中炔烃.由于产品烯烃中的炔烃等杂质含量需极低,这就对用于加氢催化剂的活性和选择性提出了很高的要求,即催化剂需要选择性吸附炔烃并加氢,而不损失其中的烯烃.经过前期大量的基础研究工作,目前工业中炔烃选择性加氢应用最广泛的催化剂是负载型钯基催化剂.然而,单独的钯金属选择性并不理想,因而对其选择性以及活性进行调控成为了当前关注的研究课题.本文采用密度泛函理论计算结合微观反应动力学模拟手段,研究了钯金属表面应力存在条件下的活性与选择性,以及形成次表层物种的可能性和形成后的活性与选择性.研究发现,改变钯金属的晶格参数与表面应力,反应物、表面反应中间体和产物的吸附能都会产生相应的变化,且吸附能与晶格参数的变化存在线性关系,晶格参数越大,吸附越强.利用表面反应过渡态能量与初始态能量之间的线性关系,相应的乙炔加氢生成乙烯的反应速率可以通过微观反应动力学模拟得到.结果显示,不同晶格参数的钯催化剂催化乙炔加氢生成乙烯的反应活性位于相应火山型曲线的强吸附侧,即减弱乙炔和氢的吸附强度可提高乙烯的生成速率.在此基础上,本文研究了不同表面应力的钯催化剂在次表面吸附不同覆盖度碳原子和氢原子的情况,发现晶格参数越大越有利于碳原子和氢原子在次表面的吸附.同时,研究发现在次表面碳掺杂的条件下,不同表面应力条件下的钯催化剂的活性均有所增强.此外,由于乙烯在所有研究的钯催化剂表面脱附比进一步加氢容易,因而乙烯都可以选择性生成.     

载体对聚硅氨烷—金属络合物催化正丙醇氧化性能的影响

1.前言 由醇类氧化脱氢,生成相应的醛和酮的反应,在工业上已有非常成熟的工艺。这一类反应的催化剂有铜,银等。但是,由于需要很高的反应温度,故这类反应常伴有CO_2、CO、H_2、羧酸、烯烃、烷烃等副产物。 我们曾发现,以SiO_2为载体的聚硅氨烷-铂络合物对甲醇、乙醇等的氧化具有较高的催化活性和选择性,在较低反应温度下,可完全生成相应的醛。但这种催化剂对正丙醇氧化的催化活性却不是很高,于100℃,5MPa下反应8h,丙醛的收率仅约为60％。 最近我们发现,负载络合物的载体对催化剂的活性有很大的影响。     

过渡金属催化的炔烃复分解反应

综述了过渡金属均相催化的炔烃复分解反应进展,主要分为两部分：一是炔烃复分解反应在炔烃合成中的应用,即从六、七十年代Mortreux催化剂的发现能均相催化炔烃的歧化反应,经过一系列的条件改造,合成了炔醚和二芳基乙炔等化合物,并提出了可能的两种机理：金属卡宾和金属卡拜机理;金属钼和钨的卡拜络合物相继合成,发现此类络合物能够催化官能化的二炔的复分解反应,合成一系列的大环化合物。二是炔烃复分解反应在合成高聚物中的应用,即钙和钨的卡拜络合物被用来催化ROMP和ADIMET反应合成高聚物,改良了的Mortreux催化剂也能催化高聚物的生成,这些高聚物在发光器件、有机"塑料"激光、液晶显示器上都有应用。     

用石油化学原料在化学品的制备及加工方面的新方法(二)

Ⅱ.单烯烃烯烃及其再加工我们知道在粗的石油原油或天然气内并不含烯烃,但在各别石油馏分热裂可以副产它们。还应指出,用一氧化碳和氢反应合成碳氢化合物时也大量生成有这样的极富于反应的碳氢化合物。现在热裂法是烯烃工业制备及再加工的主要来源。石腊碳氢化合物分裂为低级烷烃或烯烃的反应须在高温进行,全部热裂时可用也可不用催化剂。     

High-stability hydrogenated silicon-carbon clusters: a full study of Si2C2H2 in comparison to Si2C2, C2B2H4, and other similar species

The structural and electronic characteristics of the Si2C2H2 and Si2C2 clusters are studied by ab initio calculations based on coupled cluster and density functional theory using the hybrid B3LYP functional. In addition, similar species, such as SiC2H2 and Si3C2H2, are also studied for comparison. It is illustrated that the lowest energy structures of all three hydrogenated clusters, which have the general form Si(n)(CH)2, n = 1, 2, 3, are fully analogous to the structures of the corresponding organometallic isovalent carboranes. The most stable structure of Si2C2H2 is obtained by attaching two hydrogens onto the carbon atoms of a higher energy (+1.5 eV) planar trapezoidal structure of Si2C2, followed by geometry optimization which leads to puckering of the planar structure. Furthermore, it is demonstrated that Si2C2H2 and the other two "similar" hydrogenated clusters are much more stable than the corresponding bare nonhydrogenated clusters. Comparison of Si2C2H2 and C2B2H4 shows that their structural and bonding similarity includes also nuclear rearrangement similarity. The two species are isomerizable with an energy difference between their lowest energy puckered 1,2- and 1,3-isomers of about +/-0.3 eV. It is suggested that SiC2H2, Si2C2H2, and Si3C2H2 are special cases of a larger class of stable clusters. It is speculated on the basis of the calculated infrared spectrum that Si2C2H2 and perhaps other members of this class of clusters could be found in appreciable abundance in interstellar space.     

Ab initio studies of internal rotation barriers and vibrational frequencies of (C2H2)2, (CO2)2, and C2H2-CO2

We have performed large-scaleab initio calculations using second order Møller-Plesset perturbation theory (MP2) on the three van der Waals dimers formed from acetylene and carbon dioxide. Intermolecular geometrical parameters are reliably computed at this level of theory. Calculations of vibrational frequencies of the van der Waals modes, currently unobtainable by experimental means, give important information about the intermolecular potential and predict significant large-amplitude motion. Zero point energy contributions are shown to be vital in assessing the relative stability of conformations which are close in energy. Our studies suggest that the barrier to interconversion tunnelling in (CO₂)₂ is significantly smaller than previously inferred and is approximately the same as in (C₂H₂)₂. The reason for the rigidity of (CO₂)₂ is the difference in monomer centre-of-mass separation between ground state and transition state. We also show that, in addition to the previously observedC _2v form, the collinear form of C₂H₂-CO₂ is a local minimum on its potential energy surface.     

H2O2-Na2S2O3反应对pH和反应物起始浓度比的依赖性

在H2O2-Na2S2O3反应体系中，pH值和[H2O2]0/[Na2S2O3]0对反应产物的浓度大小起着关键作用.本文通过考察这两种因素对反应产物的影响，以及对反应机理的模拟，得出了pH值和氧化剂与还原剂浓度比影响反应产物浓度的一般规律.结果表明：pH< 3时，反应主要生成单质硫， 3< pH< 6时， 较为稳定，提高pH和[H2O2]0/[Na2S2O3]0有利于SO42-生成，在中性或弱碱性溶液中S(Ⅳ)(HSO42-或SO32-)物质浓度出现峰值.     

Ground electronic states of RbO2+, CsO2+ and FrO2: the ionization energies of RbO2 and CsO2

Calculations are performed to establish the ground electronic states of RbO2+, CsO2+, and FrO2. In the case of the cations, both linear and C2v orientations were considered; for FrO2, the two lowest electronic states, 2A2 and 2B2, were considered in C2v symmetry. In addition, calculations were also performed on the x2 A2 ground states of RbO2 and CsO2 to derive ionization energies. Binding energies and heats of formation are also derived. The bonding in FrO2 is found to be less ionic than that of RbO2 and CsO2.     

Ab initio investigation of the potential energy surfaces of C2H2F2 and C2H2F2+

Ab initio MO calculations have been performed for neutral and cationic C₂H₂F₂ structures. Olefinic and carbene structures are investigated for the neutral isomers, while olefinic, carbene, and fluoronium-type cations are found. Stability orders and rotational barriers are discussed in terms of orbital and Coulomb interaction. Contrary to previous studies, the higher stability of the geminal isomers is interpreted to be caused by Coulomb attraction.     

纳米ZrO2在O2/H2气中的表面效应

用ESR方法研究了一种纳米ZrO₂在普通H₂气中升温条件下的表面效应.ZrO₂上Zr³⁺的中心量约为1×10^-7mol/g.这些Zr³⁺中心是ZrO₂表面一些O^2-配位不饱和的Zr原子点位.在普通H₂气中,ZrO₂上的Zr³⁺中心数在温度低于400℃时变化很小.但在这一温度范围内从室温升温时,由ZrO₂表面羟基的H₂还原引起的F中心量随温度的升高而增加.温度高于400℃时,ZrO₂表面的Zr³⁺及F中心可与普通H₂气中存在的少量O₂气作用产生O₂^-,并伴随ZrO₂表面羟基的脱除而形成新的Zr³⁺.     

(Cl_2AlNH_2)_n和(H_2AlNH_2)_n(n=1～ 5)簇结构及其热力学性质

用 HF自洽场理论和密度泛函理论 (DFT)的 B3LYP方法 ,在 6 31G水平上研究了低聚物 (Cl2AlNH2)n和 (H2AlNH2)n(n=1～ 5)簇的几何构型、电子结构和聚合反应热力学性质 ,比较了两个系列化合物中化学键的强度 .结果表明 ,Cl2AlNH2和 H2AlNH2分子为 C2υ (EC)平面型结构 ,其中 Al－ N为由一个σ键和一个π键组成的双键 .(Cl2AlNH2)n和 (H2AlNH2)n(n=1～ 5)分子为 Dnh对称 ,Al－ N是典型的σ单键 .低聚物 (Cl2AlNH2)n和 (H2AlNH2)n的稳定性顺序分别为 : 3 > 2 > 4> 5 > 1和 8 > 7 > 9 > 11 > 6.     

非线性体系S~2O~8^2^——ClO~2^——S^2^-化学反应研究

对于新发现的S~2O~8^2^--ClO~2^--S^2^-体系在CSTR实验中铂电位的振荡现象、以及Batch实验中铂电位、pH值的非线性现象进行了报道。分析了该体系的自催化过程,提出了反应的几个步骤所对应的化学方程式,并且对自催化机理进行了初步的分析。     

Synthesis and reactions of 2-chloro- and 2-tosyloxy-2'-deoxyinosine derivatives

Convenient syntheses of 2-chloro- and 2-tosyloxy-2'-deoxyinosine as their tert-butyldimethylsilyl ethers are described. Both compounds can be synthesized via a common route and rely on commercially available 2'-deoxyguanosine. The present method leading to the chloro nucleoside is operationally simpler compared to previously reported glycosylation techniques where isomeric products were obtained. Both electrophilic nucleosides can be used for the preparation of N-substituted 2'-deoxyguanosine analogues via displacement of the leaving groups, and a comparison of their reactivities shows the chloro analogue to be superior. Interestingly, a Pd catalyst-mediated, two-step, one-pot conversion of an allyl-protected chloro nucleoside intermediate to the final modified 2'-deoxyguanosine derivatives is also feasible. On the basis of these observations, initial assessments of Pd-catalyzed aryl amination as well as a C-C cross-coupling have also been performed with the chloro and tosyloxy nucleoside substrates. Results indicate a potentially high synthetic utility of 2-chloro-2'-deoxyinosine and in many instances this derivative can supplant the bromo and fluoro analogues that are more cumbersome to prepare or are not readily available.     

Structure and properties of single crystalline CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2

Single crystals of CaMg(2)Bi(2), EuMg(2)Bi(2), and YbMg(2)Bi(2) were obtained from a Mg-Bi flux cooled to 650 °C. These materials crystallize in the CaAl(2)Si(2) structure-type (P ?3m1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg(2)Bi(2) displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg(2)Bi(2) reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) × 10(19) cm(-3) for CaMg(2)Bi(2), 1.7(1) × 10(19) cm(-3) for EuMg(2)Bi(2), and 4.6(7) × 10(19) cm(-3) for YbMg(2)Bi(2), which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios ρ(300 K)/ρ(10 K) ≤ 1.6 in all cases, indicating significant defect scattering.