Department of Chemistry, University of California, Berkeley, California 94720, United States.
J Am Chem Soc. 2020 Jun 10;142(23):10494-10505. doi: 10.1021/jacs.0c03301. Epub 2020 May 21.
Phenanthroline ligands and [Ir(cod)(OMe)] form complexes that catalyze the silylation of aromatic and aliphatic C-H bonds. However, no experimental data on the identity of complexes related to the mechanism of this process or the mechanisms by which they react to functionalize C-H bonds have been reported. Herein, we describe our studies on the mechanism of the iridium-catalyzed silylation of aryl C-H bonds. The resting state of the catalyst is an iridium disilyl hydride complex (phenanthroline)Ir(SiMe(OTMS))(H)(L), in which L varies with the arene and additives. An iridium disilyl hydride complex was isolated, characterized, and allowed to react with arenes to form aryl silanes. The kinetics of the reactions of electron-rich and electron-poor arenes showed that the rate-limiting step varies with the electronic properties of the arene. Computational studies on related iridium silyl complexes revealed that the high activity of iridium complexes containing sterically encumbered phenanthroline ligands is due to a change in the number of silyl groups bound to iridium between the resting state of the catalyst containing the hindered phenanthroline and that containing less-hindered phenanthroline.
菲咯啉配体与[Ir(cod)(OMe)]形成配合物，可催化芳族和脂肪族 C-H 键的硅烷化反应。然而，对于与该过程的机理相关的配合物的身份或它们反应以官能化 C-H 键的机理的实验数据尚未报道。在此，我们描述了我们对铱催化芳基 C-H 键硅烷化反应机理的研究。催化剂的静止状态是铱二硅基氢化物配合物(phenanthroline)Ir(SiMe(OTMS))(H)(L)，其中 L 随芳烃和添加剂而变化。分离出并表征了一种铱二硅基氢化物配合物，并允许其与芳烃反应形成芳基硅烷。富电子和缺电子芳烃的反应动力学表明，限速步骤随芳烃的电子性质而变化。对相关铱硅基配合物的计算研究表明，含有空间位阻菲咯啉配体的铱配合物的高活性是由于在含有受阻菲咯啉的催化剂的静止状态和含有较少位阻的菲咯啉的催化剂之间，与铱结合的硅基数目发生变化。
