Reactive Cationic Zr(IV) and Ti(IV) Complexes Containing Labile Ligands

齐格勒-纳塔催化剂广泛用作聚合物合成的工业催化剂。 本项目将研究的锆和钛化合物与可溶性齐格勒-纳塔催化剂有关。 该项目预计将有助于更好地了解这些催化剂的功能，并提供设计更具体、更高效的聚合物合成催化剂所需的信息。 已经发现了用于合成和分离双-Cp-Zr(R)(L)类型的阳离子有机锆络合物的一般方法，其中L是不稳定配体。 有机锆配合物具有高反应性。 它们的 Zr-R 键可快速插入酮、腈和其他极性不饱和底物，并且 THF 络合物在没有 A1 助催化剂的情况下聚合乙烯。 这些观察结果支持了最近提出的观点，即阳离子 Ti 和 Zr 络合物是可溶性齐格勒-纳塔催化剂体系中的活性物质。 阳离子有机锆配合物也容易氢化成合成上有用的阳离子氢化物。 该研究计划是合成一系列广泛的 Cp2M(R)(L) 配合物（M = Ti, Zr），并研究它们与烯烃和其他不饱和底物以及氢的反应范围和机制。 这些新型化合物为研究 M-R 键（M = Ti、Zr）插入反应的基本特征提供了机会，而没有 A1 助催化剂引起的许多并发症。 该项目还包括开发基于手性阳离子 Cp2M(R)(L) 配合物的不对称有机合成的研究。

Ziegler-Natta catalysts are used widely as industrial catalysts for the synthesis of polymers. The zirconium and titanium compounds which will be studied in this project are related to soluble Ziegler-Natta catalysts. This project is expected to provide a better understanding of how these catalysts function and to provide information needed to design more specific and more efficient catalysts for polymer synthesis. General methods for the synthesis and isolation of cationic organozirconium complexes of the type bis-Cp-Zr(R)(L) where L is a labile ligand have been discovered. The organozirconium complexes are highly reactive. Their Zr-R bonds undergo rapid insertion of ketones, nitriles and other polar unsaturated substrates, and the THF complexes polymerize ethylene in the absence of an A1 cocatalyst. These observations support recent proposals that cationic Ti and Zr complexes are active species in soluble Ziegler-Natta catalyst systems. The cationic organozirconium complexes are also easily hydrogenated to synthetically useful cationic hydrides. The research plan is to synthesize an extensive series of Cp2M(R)(L) complexes (M = Ti, Zr) and to study the scope and mechanisms of their reactions with olefins and other unsaturated substrates, and with hydrogen. These novel compounds provide an opportunity to study the fundamental features of insertion reactions of M-R bonds (M = Ti, Zr) in the absence of the many complications caused by A1 cocatalysts. Also included in this project is research to develop asymmetric organic syntheses based on chiral cationic Cp2M(R)(L) complexes.