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

加州理工学院化学系John E.Bercaw博士得到化学部无机、生物无机和有机金属化学计划的支持，该计划旨在对具有反应性配体的早期过渡金属络合物进行合成、结构和机理研究。将制备一系列路易斯酸性基团4和5金属络合物，它们包含配位配体中包含的相邻的刘易斯碱位。由于这些化合物的两性性质，将为H-X sigma键的活化开辟新的途径，并可以通过控制pH来调节金属的氧化状态。将确定新反应类型的机理，并与更常见的弯曲夹心金属类似物进行比较。基于过渡金属化合物的催化剂在化学工业中得到了广泛的应用，有机过渡金属化学的重要新进展往往集中在开发新的催化剂或优化现有的催化剂上。这项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“非无害”基团。这些基团被称为配体，它们将带有活性位点，使过渡金属的行为能够以新颖的、系统的方式改变。新化合物应能激活与氢有关的键，并可催化烯烃聚合。最终目标是开发催化剂，选择性地将碳氢化合物、水和氨等容易获得的物质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.