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Elucidation of the Reaction Mechanisms of Hydrosilylations with Cationic Transition-Metal Catalysts

阳离子过渡金属催化剂氢化硅烷化反应机理的阐明

基本信息

批准号：
427411484
负责人：
Professor Dr. Martin Oestreich
金额：
--
依托单位：
Institut für Chemie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2019
资助国家：
德国
起止时间：
2018-12-31 至 2022-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/427411484?language=en
关键词：
Elucidation Reaction Mechanisms Hydrosilylations Cationic

项目摘要

The mechanistic understanding of chemical reactions is a fundamental requirement for their further development. We have been engaged for quite a while in the experimental elucidation of the ionic hydrosilylation of carbonyl compounds catalyzed by main-group Lewis acids and transition-metal complexes, respectively. The key insight of our preliminary work is that those hydrosilylation reactions that are promoted by cationic transition-metal catalysts do not proceed by their postulated reaction mechanisms. Our laboratory showed for two prominent cases that the neutral transition-metal hydride formed as an intermediate during the catalysis is not sufficiently hydridic to reduce the silylcarboxonium ion. Another molecule of the hydrosilane is needed to activate that transition-metal hydride either by coordination or even oxidative addition of the Si‒H bond (two-silicon rather than one-silicon cycle). Hence, more than one equivalent of the hydrosilane is required to accelerate and drive these hydrosilylations to completion. The consequences of this finding are far-reaching as it means that reported mechanisms of related hydrosilylation reactions are also likely to require partial revision. Within this project, we verify the generality of our hypothesis by systematically looking into the mechanisms of two additional representative carbonyl hydrosilylations. We hope that a universally valid mechanistic picture will evolve from this.

从机理上理解化学反应是化学反应进一步发展的基本要求。我们对主基Lewis酸和过渡金属络合物分别催化的羰基化合物的离子硅氢加成反应进行了很长一段时间的实验研究。我们前期工作的关键是，那些由阳离子过渡金属催化剂促进的硅氢加成反应并不是按照其假设的反应机理进行的。我们的实验室在两个突出的例子中表明，在催化过程中作为中间体形成的中性过渡金属氢化物不够氢化，不足以还原硅基碳离子。氢硅烷的另一个分子需要通过配位或甚至通过硅-氢键的氧化加成来激活过渡金属氢化物(两个硅而不是一个硅循环)。因此，需要不止一种当量的氢化硅烷来加速和推动这些氢化硅烷化反应完成。这一发现的结果是深远的，因为它意味着已报道的相关硅氢加成反应的机制也可能需要部分修改。在这个项目中，我们通过系统地研究另外两个具有代表性的羰基硅氢化反应的机制来验证我们假设的一般性。我们希望，一个普遍有效的机械论图景将由此演变而来。