Synthetic, Structural and Mechanistic Investigations of New Derivatives of the Early Transition Metals Having Reactive Ligands

John E. Bercaw博士，加州理工学院化学系，受到化学系无机、生物无机和有机金属化学项目的支持，从事具有活性配体的早期过渡金属配合物的合成、结构和机理研究。制备了一系列含有配位配体中相邻路易斯碱基的路易斯酸性基团4和5金属配合物。由于这些化合物的两性性质，激活H-X sigma键的新途径将被打开，金属的氧化状态可以通过控制ph来调节。新反应类型的机制将被确定，并将与更常见的金属弯曲三明治类似物进行比较。基于过渡金属化合物的催化剂在化学工业中应用广泛，有机过渡金属化学的重要新进展往往集中在新催化剂的开发或现有催化剂的优化上。本研究的目的是制备和结构表征新型的早期过渡金属化合物，这些化合物含有附着在金属上的“非无辜”基团。这些被称为配体的基团将具有反应位点，从而允许以新颖的、系统的方式改变过渡金属的行为。新化合物应激活含氢键，并可能催化烯烃聚合。最终目标是开发催化剂，选择性地将现成的物质（如碳氢化合物、水和氨）转化为更有价值的产品。

Dr. John E. Bercaw, Chemistry Department, California Institute of Technology, is supported by the Inorganic, Bioinorganic, and Organometallic Chemistry Program of the Chemistry Division for synthetic, structural, and mechanistic investigations of early transition metal complexes having reactive ligands. A series of Lewis acidic group 4 and 5 metal complexes which contain adjacent Lewis base sites contained in coordinated ligands will be prepared. Because of the amphoteric nature of these compounds new pathways for the activation of H-X sigma bonds will be opened and the oxidation state of the metal can be adjusted through the control of pH. The mechanisms of new reaction types will be determined and comparisons will be made with the more usual bent sandwich analogues of the metals. Catalysts based on transition metal compounds are used extensively in the chemical industry and important new developments in organo-transition metal chemistry often center on the development of new catalysts or on the optimization of existing ones. The objective of this research is to prepare and structurally characterize new types of early transition-metal compounds that contain `non-innocent` groups attached to the metal. These groups, called ligands, will bear reactive sites that will allow the behavior of the transition metal to be altered in novel, systematic ways. The new compounds should activate bonds involving hydrogen and may catalyze olefin polymerization. The ultimate goal is to develop catalysts to selectively transform readily available substances such as hydrocarbons, water, and ammonia into more valuable products.