Heterolytic Oxidative Addition of sp2 and sp3 C-H Bonds by Metal-Ligand Cooperation with an Electron-deficient Cyclopentadienone Iridium Complex
Heterolytic Oxidative Addition of sp2 and sp3 C-H Bonds by Metal-Ligand Cooperation with an Electron-deficient Cyclopentadienone Iridium Complex
复制标题
通过金属配体与缺电子环戊二烯酮铱络合物的合作进行 sp2 和 sp3 C-H 键的杂解氧化加成
DOI：
10.1021/jacs.1c06714
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发表时间：
2022
影响因子：
15
通讯作者：
K. Nozaki
中科院分区：
文献类型：
--
作者：
T. Higashi;S. Kusumoto;K. Nozaki
C-H键的氧化加成反应生成含金属碳键的反应中间体，在有机金属化学中起着重要的作用。本文中，我们制备了一种用于氧化C-H键加成的环戊二烯酮铱（I）配合物1。该配合物裂解各种sp2和sp3 C-H键，包括己烷和甲烷中的那些，从它们的H/D交换反应推断。当配合物与硝基甲烷反应时，生成了羟基三硝基甲基铱（III）配合物2，这突出了这一基本的金属-配体C-H键氧化加成反应。机理研究表明，C-H键断裂是由基底或另一种铱配合物中的极性官能团介导的。我们发现，更缺电子的配体导致更有利的反应，与经典的金属为中心的氧化加成形成鲜明对比。这一趋势与所提出的机理非常一致，其中C-H键断裂伴随着从金属中心到环己烯酮配体的双电子转移。该配合物进一步应用于四氢呋喃（THF）的催化转移脱氢反应。
Oxidative addition reactions of C–H bonds that generate metal–carbon-bond-containing reactive intermediates have played essential roles in the field of organometallic chemistry. Herein, we prepared a cyclopentadienone iridium(I) complex1designed for oxidative C–H bond additions. The complex cleaves the various sp2and sp3C–H bonds including those in hexane and methane as inferred from their H/D exchange reactions. The hydroxycyclopentadienyl(nitromethyl)iridium(III) complex2was formed when the complex was treated with nitromethane, which highlights this elementarymetal–ligand cooperative C–H bond oxidative additionreaction. Mechanistic investigations suggested the C–H bond cleavage is mediated by polar functional groups in substrates or another iridium complex. We found that ligands that are more electron-deficient lead to more favorable reactions, in sharp contrast to classical metal-centered oxidative additions. This trend is in good agreement with the proposed mechanism, in which C–H bond cleavage is accompanied by two-electron transfer from the metal center to the cyclopentadienone ligand. The complex was further applied to catalytic transfer-dehydrogenation of tetrahydrofuran (THF).