The Synthesis of New Compounds Containing Metal Clusters Using Designed Superlattice Reactants to Control the Kinetics and Reaction Mechanism

利用设计的超晶格反应物控制动力学和反应机制合成含金属簇的新化合物

• 批准号: 9510562
• 负责人: David Johnson
• 金额: $ 34.34万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-11-15 至 1998-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9510562&HistoricalAwards=false
• 关键词: Synthesis; New; Compounds; Containing; Metal

9510562 Johnson This proposal focuses upon the synthesis of new ternary transition metal chalcogenides which contain discrete clusters of transition metal atoms. The ternary molybdenum chalcogenides and the alkali metal intercalates of the fullerines are both examples of this class of compounds, containing discrete but interacting cluster entities. Both of these classes of materials have been found to have a host of unusual properties ranging from catalytic activity to superconductivity which have been rationalized as resulting from the unique cluster structure found in these materials. The goal is to prepare tungsten, niobium and tantalum compounds which are isostructural analogs of the ternary molybdenum chalcogenides. The preparation of isostructural and isoelectronic compounds to the ternary molybdenum compounds will permit the testing of these structure based arguments and will hopefully extend the range of properties found in this unique class of materials which is some sense bridges the gap between discrete molecular compounds and extended structures . %%% Chemical reactions involving solids at low temperatures are very sluggish even though there is often a large driving force for the reactions. Previous attempts to prepare new ternary transition metal chalcogenides which contain discrete clusters of transition metal atoms via reactions between the elements have only produced mixtures of binary compounds or other ternary structures. This is probably because the desired compounds are thermodynamically unstable with respect to the known compounds in these phase diagrams. Consequently, the key to the success to their synthesis will be avoiding the formation of stable binary compounds as reaction intermediates. Towards this end, a kinetically controlled route to solid-state compounds is developed based upon the design of elemental superlattices as uniquely tailorable reactants. This approach separates the two key steps of a solid state reaction - interdi ffusion of the reactants and nucleation of the products. Since product formation is controlled by the lucleation barriers, one is able to kinetically control the product formed. The development of synthetic tools to nucleate desired structures is a significant part of the proposed research.

9510562约翰逊 该建议的重点是合成新的三元过渡金属硫属化物，其中包含离散的过渡金属原子簇。三元钼硫族化物和富勒烯的碱金属嵌入物都是这类化合物的例子，含有离散但相互作用的簇实体。这两类材料都被发现具有许多不寻常的性质，从催化活性到超导性，这些性质被合理化为这些材料中发现的独特簇结构。 目标是制备钨、铌和钽化合物，它们是三元钼硫属化物的同构类似物。三元钼化合物的等结构和等电子化合物的制备将允许测试这些基于结构的参数，并将有望扩展在这类独特材料中发现的性质范围，这是离散分子化合物和扩展结构之间的差距的某种意义上的桥梁。 固体在低温下的化学反应非常缓慢，即使反应通常有很大的驱动力。先前通过元素之间的反应制备含有过渡金属原子的离散簇的新的三元过渡金属硫属化物的尝试仅产生二元化合物或其它三元结构的混合物。这可能是因为所需的化合物相对于这些相图中的已知化合物是化学不稳定的。 因此，其合成成功的关键将是避免形成稳定的二元化合物作为反应中间体。为此，一个动力学控制的路线，固态化合物的基础上开发的元素超晶格的设计独特的裁缝反应物。这种方法分离了固态反应的两个关键步骤-反应物的相互扩散和产物的成核。由于产物的形成是由成核屏障控制的，因此能够在动力学上控制所形成的产物。开发合成工具来使所需结构成核是所提出的研究的重要组成部分。