光电子能谱(五)

3.配位络合物在过渡金属原子形成的阳离子周围,由一些中性分子和(或)阴离子所环绕,从而生成具有一定形式的配位络合物,这些中性分子及阴离子就称为配位体。配位体的活性有赖于中心离子的性质。配位体接近带高电荷的金属中心离子时,引起分子中的极化,或当配位体将它的电子供给一个阳离子共享后就会发生许多变化,其中最重要的是使给电子原子上的其它键减弱。一系列电子给予体和金属配位时,它将孤对电子或π电子输送给中心过渡金属的空d轨道成σ键,同时充满电子的适当金属d轨道将电子回送给配位基的空反键轨道成dπ-pπ键。由于配位基的不同,金属氧化态的不同,σ给电子能力和π受电子能力有差异,因此金属配合物的活性及配位体中的键强也有差别。光电子能谱通过结合能的测定可以提供电荷转移的信息,成为研究配位键性质的一种工     

过渡金属络合催化活性顺序的量子化学研究（Ⅲ）：对氧分子的活化

本文用我们自己建立的以ＨＭＯ为主的量子化学方法研究了过渡金属对氧分子的活化问题。研究结果表明，它不仅可以讨论过渡金属对氧分子的催化活性顺序以及络合方式和配位体对催化活性的影响，而且可以讨论过渡金属的催化活性随底分子迁移的规律以及可逆载氧体的结构和性能之间的关系。     

过渡金属络合催化活性顺序的量子化学研究（Ⅲ）─对氧分子的活化

本文用我们自已建立的以ＨＭＯ为主的量子化学方法研究了过渡金属对氧分子的活化问题。研究结果表明，它不仅可以讨论过渡金属对氧分子的催化活性顺序以及络合方式和配位体对催化活性的影响，而且可以讨论过渡金属的催化活性随底物分子迁移的规律以及可逆载氧体的结构和性能之间的关系。     

聚合物载体-稀土金属络合物的研究——Ⅶ.聚合物载体-金属络合物的微观结构与络合物催化聚合丁二烯活性的关系

众所周知,在烯烃络合催化聚合中,过渡金属配位体的种类是影响催化剂活性的重要因素之一.用高分子代替小分子作为配位体,影响催化剂的活性因素则由原来单一的固定因素变成多重的可变因素.高分子金属络合物的结构因素,如金属含量、功能团含量,金属与功能团的含量比都将直接影响催化活性.本文从聚合物的微观结构角度,研究了作为载体的苯乙烯-丙烯酸共聚物中单体单元的序列分布及其与催化活性的关系.     

3d夹心化合物的电子结构

用EHMO方法研究了3d环戊二烯夹心化合物的电子结构。结果表明环戊二烯配位体和过渡金属的化学键,Cp-M,含有σ、π和δ三种键型。以π给予键为主,σ和δ键主要是金属轨道的贡献。讨论了这三种键型对3d过渡金属环戊二烯夹心化合物稳定性的影响。     

希土冠醚配合物的电子结构

本文用INDO方法计算了希土冠醚配合物的分子构型、电子结构、电荷分布和键级,讨论了配位前后电荷分布特征,以及由于配位引起L→L_n电荷转移跟配合物电子结合能化学位移和配位活化的关系,解释了因冠醚内腔不同希土冠醚配合物呈现不同构型的内在原因。希土冠醚配合物的占据分子轨道以配位体轨道成分为主体(4f轨道除外),低空轨道以希土原子轨道成分为主体。其占据分子轨道可分为六组。冠醚环上引入苯环后配合物前线轨道呈现π键性质。其价键的主要贡献部份是5d轨道,其次是6p和6s。4f轨道基本上不参与成键。讨论了配合物的化学键性质及高配位数时稳定的因素。     

烯烃加氢催化剂—聚丙烯腈-钯络合物

近年来出现了用过渡金属化合物和具有官能团的高聚物络合的所谓高分子催化剂.这种催化剂在催化某些反应上具有活性高,选择性好,容易分离及反应条件温和等优点.因此引起人们的重视. 我们用聚丙烯腈为配位体与带结晶水的氯化钯制备了聚丙烯腈-钯络合物.该络合物在催化庚烯-1的加氢时显示良好的催化活性,并且催化活性明显地受到络合物中N/Pd     

过渡金属配合物结构理论的角重叠模型及其应用

过渡金属配合物结构理论中,目前应用最广的是晶体场-配位场理论和分子轨道理论。应用分子轨道理论处理配位化合物原则上是最优越的,但为了得到每个分子轨道的构成和能量,通常需进行冗长复杂的计算,而且从一个配合物所得的结果一般不适用于别的配合物。同     

Rh(Ⅰ),Co(Ⅰ)和Ru(Ⅱ)双齿磷氢化物的合成.结构表征和催化加氢活性

膦配位的过渡金属氢化物被看作是烯烃及其他一些不饱含有机化合物催化加氢反应及氢甲酰化反应的催化活性物种,关于它们的结构与催化活性关系的研究,有着重要的理论意义和实际意义,通常单齿膦配位表现出较高的催化活性,而不同的金属中心在催化活性和选择性上也表现出明显的差别,反映了催化功能与催化活性物种的电子结构和空间结构之间存在着依存关系.膦配体过渡金属氢化物,通常是以它们的相应卤化物经氢化锂铝或硼氢化钠或肼还原得     

含氮、硫螯合树脂与Au(Ⅲ)的螯合性能和状态

用光电子能谱(ESCA)和红外光谱等方法测定了螯合树脂中N(ls)、S(2p)和Au(Ⅲ)的电子结合能和络合状态,结果说明N、S都参与了和Au(Ⅲ)的络合,N上的孤对电子向Au(Ⅲ)转移形成配键,而配位基>S除它的价层电子向Au(Ⅲ)转移形成配键外,还有Au(Ⅲ)的5 d轨道上的电子向S(3 d)空轨道转移形成反馈键,但是σ电子给出和π电子接受的作用不一定在同一个配位基>S上发生。     

Effect of catalyst transition metal and ancillary ligand on syndiospecific polymerization of styrene

In the coordination polymerization of styrene, selected transition metal complexes of metals other than group 4 elements and non-metallocenes have been investigated in comparison to a known half-metallocene titanium complex with regard to the catalytic activity as well as to the thermal and molecular properties of the polymers synthesized. Whereas iron catalysts lead to syndiotactic polystyrenes, catalysts with nickel as the transition metal result only in atactic polymers with an enhanced isotactic content.In addition to the influence of the transition metal, the effect of a broad variation of the ancillary ligands of a specific half-sandwich titanocene, octahydrofluorenyl titanium trimethoxide, on polymerization activity and polymer properties has been investigated and discussed in detail.     

Concerted and Stepwise Mechanisms in Metal‐Free and Metal‐Assisted [4+3] Cycloadditions Involving Allyl Cations

The thermal [4+3] cycloaddition reaction between allenes and tethered dienes (1,3‐butadiene and furan) assisted by transition metals (Au^I, Au^III, Pd^II, and Pt^II) was studied computationally within the density functional theory framework and compared to the analogous non‐organometallic process in terms of activation barriers, synchronicity and aromaticity of the corresponding transition states. It was found that the metal‐mediated cycloaddition reaction is concerted and takes place via transition structures that can be even more synchronous and more aromatic than their non‐organometallic analogues. However, the processes exhibit slightly to moderately higher activation barriers than the parent cycloaddition involving the hydroxyallylic cation. The bond polarization induced by the metal moiety is clearly related to the interaction of the transition metal with the allylic π* molecular orbital, which constitutes the LUMO of the initial reactant. Finally, replacement of the 1,3‐butadiene by furan caused the transformation to occur stepwise in both the non‐organometallic and metal‐assisted processes.     

过渡金属掺杂亚铁锌双金属氰化物催化合成生物柴油的研究

研究了掺杂过渡金属盐(La、Ce、Zr、Mn)对亚铁锌双金属氰化物(DMC)固体酸催化剂合成生物柴油的影响,并采用XRD、FT-IR、ICP、BET等方法对其进行结构和性能表征。结果表明,1%的镧、铈、锆、锰金属盐对催化剂的活性都有提高,其中,添加1%镧的DMC催化剂活性最高,在醇油摩尔比16∶1,反应温度160 ℃,催化剂加入量2%条件下,反应7 h,脂肪酸甲酯收率达到99.3%。过渡金属盐引入对催化剂的组成没有影响,但使得催化剂更加分散,颗粒粒径更小,比表面积变大,有利于催化剂和反应物的接触,从而提高了催化剂活性。     

后过渡金属催化烯烃可控/活性聚合的研究进展

烯烃活性聚合由于可以制备出预定分子量的窄分布聚合物,以及各种嵌段共聚物、末端功能化聚合物等而受到广泛关注.过渡金属催化的烯烃配位聚合反应活性高,催化剂性能可通过配体结构的修饰进行调节,聚合物微观结构易于调控,其活性聚合进一步拓展了对烯烃聚合物分子设计的手段,具有重要的意义.除了以钛、锆、钒等为金属中心的前过渡系催化剂之...     

Simulation of highly emissive states based on ligand-to-metal charge transfer

Properties of the frontier orbitals of a d⁰-organometallic complex with promising photoluminescent and photosensor characteristics have been systematically studied by modern quantum-chemical methods. It has been demonstrated that the lowest electronically excited states are related to charge transfer from high-lying ligand-centered molecular orbitals to the predominantly metal-centered lowest unoccupied molecular orbital. Such an approach makes it possible to predict complexes with promising spectral-luminescent properties, including catalytic precursors of early transition metals.     

A novel redox system consisting of π-conjugated polymers and transition metals

Coordination of π-conjugated polymers to transition metals constructs a novel redox system due to interchangeable various oxidation states of the polymers, which permits transition metals to interact with each other through a π-conjugate chain. The redox characteristics were found to depend on the electronic interaction with metals and the doping. A combination of copper(II) or iron(III) chloride and polyanilines afforded the complex catalysts with the higher oxidation capability for dehydrogenative oxidation. A catalytic system was also realized in the transition-metal-induced oxidation reaction, in which π-conjugated polymers serve as redox-active ligands participating in the reversible redox cycle. The Wacker oxidation of terminal olefins proceeded catalytically in the presence of a catalytic amount of polyaniline or polypyrrole derivative under oxygen.     

Orbital phase in Suzuki–Miyaura cross-coupling reactions

We investigated the electronic structures of the transition states of the oxidative addition, transmetalation, and reductive elimination steps in the catalytic cycle of the title reaction. The frontier orbital theory was surprisingly found to be applicable whereas any d orbitals of transition metals can be a main component of frontier orbitals because of their close energies. Visualizing the actually calculated HOMO and LUMO of the two parts of the transition structure of each step clearly demonstrated their orbital phase matching in favor of overlapping. The HOMO for the transmetalation step suggests that electron-donating ability of the carbon–metal bond of organometallic compounds (RMX) could control the reactivities of related cross-coupling reactions. The energies of the molecular orbitals having large amplitudes of the C–M bonding orbitals of RMX explain why the Suzuki–Miyaura cross-coupling reaction needs a base while the Kumada–Tamao and Negishi reactions take place without any bases.     

Insulated π-conjugated metallopolymers

Recently, there has been a progressive development of insulated π-conjugated metallopolymers with accumulated features of π-conjugated bridging units, transition metal complexes, and encapsulating moieties, as higher-order functionalized materials. A number of insulated conjugated metallopolymers have been successfully synthesized and their fascinating properties have been reported. In addition to the conventional features derived from π-conjugation and transition metals, their insulated structures can compensate for solubility, a disadvantage in conventional metallopolymers, and enhance their functionalities, such as sensing, luminescence, and conduction. In this review, we summarize the synthetic methodologies, structural characteristics, and functionalities of one-dimensional insulated π-conjugated metallopolymers, while focusing on the effect of transition metals and insulation on their properties.     

Enhancement of the third-order nonlinear optical properties in open-shell singlet transition-metal dinuclear systems: effects of the group, of the period, and of the charge of the metal atom

Metal-metal multiply bonded complexes in their singlet state have been predicted to form a novel class of "σ-dominant" third-order nonlinear optical compounds based on the results of dichromium(II) and dimolybdenum(II) systems (H. Fukui et al. J. Phys. Chem. Lett.2011, 2, 2063) whose second hyperpolarizabilities (γ) are enhanced by the contribution of the dσ electrons with an intermediate diradical character. In this study, using the spin-unrestricted coupled-cluster method with singles and doubles as well as with perturbative triples, we investigate the dependences of γ on the group and on the period of the transition metals as well as on their atomic charges in several open-shell singlet dimetallic systems. A significant enhancement of γ is observed in those dimetallic systems composed of (i) transition metals with a small group number, (ii) transition metals with a large periodic number, and (iii) transition metals with a small positive charge. From the decomposition of the γ values into the contributions of dσ, dπ, and dδ electrons, the γ enhancements are shown to originate from the dσ contribution, because it corresponds to the intermediate diradical character region. Furthermore, the amplitude of dσ contribution turns out to be related to the size of the d(z(2)) atomic orbital of the transition metal, which accounts for the dependence of γ on the group, on the period, and on the charge of the metal atoms. These dependences provide a guideline for an effective molecular design of highly efficient third-order nonlinear optical (NLO) systems based on the metal-metal bonded systems.