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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.

对化学反应机理的理解是其进一步发展的基本要求。我们一直致力于主族刘易斯酸和过渡金属配合物催化羰基化合物离子硅氢化反应的实验研究。我们的初步工作的关键见解是，这些硅氢加成反应，促进了阳离子过渡金属催化剂不进行其假定的反应机理。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足以还原甲硅烷基碳鎓离子。需要另一个氢硅烷分子来活化过渡金属氢化物，通过配位或甚至氧化添加Si-OH键（两个硅而不是一个硅环）。因此，需要多于一当量的氢硅烷来加速和驱动这些氢化硅烷化完成。这一发现的后果是深远的，因为它意味着相关氢化硅烷化反应的报告机制也可能需要部分修订。在这个项目中，我们验证了我们的假设的一般性，通过系统地研究两个额外的代表性羰基硅氢化的机制。我们希望，一个普遍有效的机械图将由此演变。