首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Molecular hydrides of the rare‐earth metals play an important role as homogeneous catalysts and as counterparts of solid‐state interstitial hydrides. Structurally well‐characterized non‐metallocene‐type hydride complexes allow the study of elementary reactions that occur at rare‐earth‐metal centers and of catalytic reactions involving bonds between rare‐earth metals and hydrides. In addition to neutral hydrides, cationic derivatives have now become available.  相似文献   

2.
茂型稀土金属有机配合物的合成与表征研究进展   总被引:1,自引:0,他引:1  
本文综述了茂型稀土金属有机配合物的研究现状和最新进展。系统地介绍了茂型稀土金属有机配合物的特征、合成、以及结构表征方法,并着重介绍了典型三茂型、二茂型、含茚基、含芴基稀土金属有机配合物的晶体结构。最后,展望其发展趋势和研究方向。  相似文献   

3.
The optical properties of rare earth ions in different inorganic host materials, for instance oxides, silicates, borates, or nitrides, have been used in applications for many years, from color TV to fluorescent tubes, lasers, or pc‐LEDs. However, rare earth metal ion‐doped hydrides have not really been considered as host lattices and up to now only been studied in a relatively small number of investigations. Yet, for certain metal hydrides these studies, e.g., allowed the determination of the crystal field strength and nephelauxetic effect of the hydride anion using the Eu2+ 5d excited state. In air‐sensitive hydrides, the use may be restricted to fundamental studies and local probes. But recently more and more air‐stable mixed anionic hydrides have been discovered, which may serve as hosts. This short review summarizes the synthesis and characterization of rare earth metal ion‐doped hydrides reported so far.  相似文献   

4.
罗梅  苏庆德  马怀柱 《结构化学》2002,21(6):583-591
综述了茂型稀土金属有机配合物催化甲基丙烯酸酯类聚合的研究现状和最新进展。系统地介绍了不同的茂型稀土金属有机催化体系中温度、反应时间、溶剂等条件对催化甲基丙烯酸酯类聚合的影响规律,并研究其催化反应机理,最后展望茂型稀土金属有机化学今后的研究方向及前景。  相似文献   

5.
[Sc([9]aneS3)(CH2SiMe3)3], the first rare earth organometallic complex of 1,4,7-trithiacyclonane, is a precursor to ethylene and alpha-olefin polymerisation catalysts upon activation with BAr(F)3 or [CPh3][BAr(F)4](Ar(F) = C6F5); these are the first cationic rare earth organometallic catalysts supported by an all-sulfur donor ligand.  相似文献   

6.
Transition‐metal carbene complexes have been known for about 50 years and widely applied as reagents and catalysts in organic transformations. In contrast, the carbene chemistry of the rare‐earth metals is much less developed, but has attracted the research interest in the recent years. In this field rare‐earth‐metal alkylidene, especially methylidene, compounds are an emerging class of compounds with a high synthetic potential for organometallic chemistry and maybe in the future also for organic chemistry.  相似文献   

7.
胡家乐  薛冬峰 《应用化学》2020,37(3):245-255
稀土元素是一个包含了由钪、钇与镧系共17种元素的系列统称,它们既具有本质上的物理化学相似性,也具有各自独特和多样的电子结构。 从化学水平上讲,稀土离子的特性决定了稀土永磁、磁致冷、超导、热释电、光学制冷、非线性光学、催化等高新技术应用的本质;从材料水平上讲,稀土功能材料是实现这些技术应用的基础。 从科技发展要求来讲,稀土功能材料的研发是实现稀土资源高质量发展的最重要途径。 本文从稀土离子特性出发,利用轨道杂化模型构建稀土离子与稀土功能材料之间的基本关系,总结了近年来不同应用领域中稀土离子在稀土功能材料的组成设计与性能优化方面的研究进展。  相似文献   

8.
Complex aluminum hydrides have been widely studied as potential hydrogen storage materials but also,for some time now, for electrochemical applications. This review summarizes the crystal structures of alkali and alkaline earth aluminum hydrides and correlates structure properties with physical and chemical properties of the hydride compounds. The crystal structures of the alkali metal aluminum hydrides change significantly during the stepwise dehydrogenation. The general pathway follows a transformation of structures built of isolated [AlH4]~- tetrahedra to structures built of isolated [Al H6]~(3-) octahedra.The crystal structure relations in the group of alkaline earth metal aluminum hydrides are much more complicated than those of the alkali metal aluminum hydrides. The structures of the alkaline earth metal aluminum hydrides consist of isolated tetrahedra but the intermediate structures exhibit chains of cornershared octahedra. The coordination numbers within the alkali metal group increase with cation sizes which goes along with an increase of the decomposition temperatures of the primary hydrides. Alkaline earth metal hydrides have higher coordination numbers but decompose at slightly lower temperatures than their alkali metal counterparts. The decomposition pathways of alkaline metal aluminum hydrides have not been studied in all cases and require future research.  相似文献   

9.
范荫恒  武美霞  吴强  廖世健  徐杰 《中国化学》2002,20(11):1450-1452
IntroductionLanthanidehydridecanbepreparedbydirecthydro genationofthemetalprovidedthatitisfirstactivatedbyheatingto 30 0℃inhydrogen ,followedbycoolingunderhydrogen .1Usingthismethodtopreparelanthanumhy dride ,theproducthasanaveragediameteraround 5 0μm ,anditss…  相似文献   

10.
杯芳烃的配位性质   总被引:12,自引:0,他引:12  
郑炎松 《化学进展》1999,11(3):275-285
杯芳烃及其衍生物几乎能够与所有的金属形成配合物, 本文综述了杯芳烃与稀土金属, 杯芳烃与一些过渡金属的配合物, 以及杯芳烃金属有机化合物和特殊的穴内配合物。  相似文献   

11.
The organometallic approach is one of the most active topics in catalysis. The application of NH functionality in organometallic catalysis has become an important and attractive concept in catalyst design. NH moieties in the modifiers of organometallic catalysts have been shown to have various beneficial functions in catalysis by molecular recognition through hydrogen bonding to give catalyst–substrate, ligand–ligand, ligand–catalyst, and catalyst–catalyst interactions. This Review summarizes recent progress in the development of the organometallic catalysts based on the concept of cooperative catalysis by focusing on the NH moiety.  相似文献   

12.
Borohydride complexes of the rare earths have attracted increasing interest during the last decade. This review aims to cover recent results over this period with respect to the preparation, characterization, structure, and applications in organic chemistry of this family of compounds, including inorganic and organometallic complexes. Special emphasis is made on their use for polymerization catalysis.  相似文献   

13.
稀土金属的配位数较高,可通过容纳大型手性配体,构筑手性环境,催化不对称反应的定向发生,在工业生产特别是制药工程中具有重要应用价值.本文以Henry反应、Mannich反应和Strecker反应为例,总结回顾了稀土金属催化剂在此类反应中的设计思路、性能特点与应用前景,旨在展现稀土金属催化剂兼具融合均相催化与异相催化的优势...  相似文献   

14.
王绪绪 《化学通报》2001,64(8):492-498
阐述评述了表面有机金属化学形成和发展的前景、有机金属化合物与固体表面反应的基本规律和表面有机金属配合物的结构,对表面有机金属化学与催化化学的本质联系进行了讨论。  相似文献   

15.
Active-site/surface cooperativity can enhance heterogeneous organic and organometallic catalysis. We review the powerful role of the solid surface in this context for generating local acidity and, as an inner-sphere ligand, for stabilizing immobilized supramolecular assemblies and unsaturated organometallic complexes that are often unstable in solution.  相似文献   

16.
The stability and the high temperature steam resistance of Ni/Al2O3 catalysis added with rare earth oxides were investigated. It was found that the addition of rare earth oxides resulted in great improvement in the stability and high temperature steam resistance of the catalysts through suppressing the growth of Ni crystallite, the oxidation of metal Ni and the formation of NiAl2O4.  相似文献   

17.
郁楠  侯召民  席振峰 《化学进展》2008,20(10):1515-1524
阳离子型金属有机化合物是催化烯烃聚合反应的活性物种,其结构与性质直接影响所得聚合物的微观结构和性能,具有重要的研究价值。对四族金属有机化合物的深入研究也推动了对其他前过渡金属和稀土金属有机化合物的研究。与为数众多的中性及阴离子型稀土金属有机化合物相比,由于具有较高的反应性、合成与分离不易,阳离子型稀土金属有机化合物直到最近才逐渐得到重视。本文介绍了近年来在阳离子型稀土金属有机化合物的合成、结构和催化烯烃聚合反应领域的研究进展。  相似文献   

18.
This article reviews the development of dinitrogen chemistry and some associated organometallic chemistry at the University of Sussex with which the author was directly involved. The establishment of the basic heavy-element halide phosphine chemistry laid the ground for the discovery of dinitrogen complexes of rhenium, osmium, molybdenum and tungsten. From there, some of the first well-defined reactions of coordinated dinitrogen (especially protonation and alkylation) were discovered and the essential mechanisms of such reactions were established. This allowed the development of models for the action of nitrogenases that are still probably the best available. Later work has produced similar models in iron chemistry and a range of organometallic chemistry has been uncovered in the effort to discover parallels between the basic organometallic chemistry of substances such as metal carbonyls, dinitrogen complexes and hydrides in their interactions with acetylenes and cyclpropene.  相似文献   

19.
The catalytic addition of terminal alkynes to carbodiimides has been achieved for the first time by use of half-sandwich rare earth metal complexes, such as {Me2Si(C5Me4)(NPh)}Y(CH2SiMe3)(THF)2, which offers a straightforward, atom-economic route to the N,N'-disubstituted propiolamidines which contain a conjugated C-C triple bond, a new family of amidines which were difficult to prepare by other means. A rare earth metal amidinate species was confirmed to be a true catalytic species in this process, thus demonstrating for the first time that an amidinate unit, though being often used as an ancillary ligand for various organometallic complexes, can itself participate in a catalytic reaction under appropriate conditions.  相似文献   

20.
For a long time multi-component syntheses of heterocycles have undeniably been a domain of classical carbonyl condensation chemistry. However, the advent of transition-metal catalysis not only has fertilized strategies in heterocyclic synthesis by uni- and bimolecular transformations but the past decade has also witnessed a rapid development of transition-metal catalysis in new multi-component reactions (MCR). Expectedly, palladium catalyzed processes have received a dominant position, yet, other transition-metal complexes are catching up implying organometallic elementary steps that reach even further than cross-coupling and carbometallation. Besides domino MCRs that are purely based upon organometallic catalysis the sequential and consecutive combination with condensation, addition and cycloaddition steps opens a vast playground for the invention of new sequences in heterocyclic synthesis. This tutorial review outlines the underlying reaction based principles of transition-metal catalysis in multi-component syntheses of heterocycles, summarizes recent developments of palladium catalyzed MCR, and highlights the more recent contributions to MCR based heterocyclic synthesis by virtue of rhodium, ruthenium, and copper catalysis.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号