Homogeneous Models of Ziegler-Natta Catalysts

在无机、生物无机和有机金属化学项目的支持下，Gregory S. Girolami博士将合成和研究广泛用于工业合成聚乙烯等聚合物的多相催化剂的可溶性模型，即所谓的Ziegler-Natta催化剂。预计该项目的结果将有助于确定催化活性的物种，并有助于制定催化过程的详细机制。将合成和研究齐格勒-纳塔催化剂的均相模型，特别强调早期过渡元素的电子不饱和烷基衍生物的制备和反应性。要研究的影响包括意想不到的自旋态变化，这种变化是由于早期过渡金属（如第4族金属）向配体受体轨道提供了极强的pi电子而引起的。虽然Ziegler-Natta催化剂通常采用八面体结构，但d-零金属烷基也可以采用非八面体结构，本文将探讨后一种结构在催化过程中的作用。新的铬基聚合体系的研究和过渡金属烷基热裂解的机理研究也将继续进行。

With support from the Inorganic, Bioinorganic and Organometallic Chemistry Program, Dr. Gregory S. Girolami will synthesize and study soluble models of the heterogeneous catalysts used widely for the industrial synthesis of such polymers as polyethylene, the so-called Ziegler-Natta catalysts. The results of the project are expected to aid in the identification of the species responsible for the catalytic activity and in the formulation of a detailed mechanism for the catalytic process. Homogeneous models of Ziegler-Natta catalysts will be synthesized and studied, with particular emphasis on the preparation and reactivity of electronically unsaturated alkyl derivatives of the early transition elements. Among the effects to be examined are the unexpected spin-state changes which occur as a result of the extremely strong pi-electron donation by the early transition metals, e.g., those of group 4, to ligand acceptor orbitals. Although octahedral geometries are generally assumed for Ziegler-Natta catalysts, d-zero metal alkyls can adopt non-octahedral geometries, and the role of the latter geometries in the catalytic process will be probed. Studies of new chromium-based polymerization systems and mechanistic studies related to the thermolysis of transition metal alkyls will be pursued also.