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Synthesis of Mixed-Metal Metallocenoid Clusters

混合金属茂金属团簇的合成

基本信息

批准号：
23655051
负责人：
MURAHASHI Tetsuro
金额：
$ 2.33万
依托单位：
Institute for Molecular Science (2012)Osaka University (2011)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Challenging Exploratory Research
财政年份：
2011
资助国家：
日本
起止时间：
2011 至 2012
项目状态：
已结题

项目摘要

The mixed metal clusters have attracted great attention because a synergetic effect of different transition metal elements which are directly connected with each other via metal-metal bonds may give an advantage in physical properties or reactivity of metal clusters. Although much efforts have been made to incorporate different metals in a metal cluster framework, there remains a difficulty to attain a selective and efficient synthesis of tri- or higher nuclear mixed-metal clusters having a planned composition, in which the ligand environment around each metal is quasi-equivalent. The difficulty of controlling the metal stoichiometry, i.e., M_3, M_2M’, MM’_2, and M’_3, may arise not only from the thermodynamic but the kinetic factor : The incorporation rate of M to the triangular trimetal core is inherently different from that of M’, due to the different strength and reactivity of M-M, M-M’, and M’-M’ bonds. Furthermore, the ease of M-L and M’-L dissociation/association which might also be involved in the formation of trimetallic core can affect the selectivity of the mixed-metal core formations. Thus, a well-planned synthetic strategy is needed for the selective construction of M_2M’ and MM’_2 cores. In this project, we realized selective construction of the triangular PdPt_2 and Pd_2Pt cores in a common sandwich framework, where a key is to use different carbocyclic ligands for the different composite sandwich ; i.e., cycloheptatrienyl for PdPt_2, and cycloheptatriene for Pd_2Pt. After construction of the Pd_2Pt core, the cycloheptatriene ligands can be converted to cycloheptatrienyl ligands where a (carbocyclic ligand)-(metal triangle)-(carbocyclic ligand) sandwich structure was retained.

混合金属团簇引起了人们的极大关注，因为通过金属-金属键直接相互连接的不同过渡金属元素的协同效应可能会给金属团簇的物理性质或反应活性带来优势。尽管已经做出了很多努力将不同的金属纳入金属簇骨架中，但仍然难以实现具有计划组成的三核或更高核混合金属簇的选择性和有效合成，其中每种金属周围的配体环境是准等效的。控制金属化学计量（即M_3、M_2M'、MM'_2和M'_3）的难度不仅来自热力学因素，还来自动力学因素：由于M-M、M-M'和M'-M'键的强度和反应性不同，M与三角形三金属核的结合速率本质上不同于M'。此外，M-L和M'-L解离/缔合的难易程度也可能参与三金属核的形成，从而影响混合金属核形成的选择性。因此，需要一个精心策划的合成策略来选择性构建 M_2M' 和 MM'_2 核。在本项目中，我们实现了在通用夹层框架中选择性构建三角形PdPt_2和Pd_2Pt核，其中关键是针对不同的复合夹层使用不同的碳环配体；即PdPt_2为环庚三烯基，Pd_2Pt为环庚三烯。构建Pd_2Pt核后，环庚三烯配体可以转化为环庚三烯基配体，其中保留了（碳环配体）-（金属三角形）-（碳环配体）夹心结构。