Synthesis of New Cationic Cp*Ir N-Heterocyclic Carbene Complexes and Their High Catalytic Activities in the Oppenauer-Type Oxidation of Primary and Secondary Alcohols
Synthesis of New Cationic Cp*Ir N-Heterocyclic Carbene Complexes and Their High Catalytic Activities in the Oppenauer-Type Oxidation of Primary and Secondary Alcohols
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DOI：
10.1021/om0503545
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发表时间：
2005-06
期刊：
影响因子：
2.8
通讯作者：
Fumihiro Hanasaka;and Ken-ichi Fujita;R. Yamaguchi
中科院分区：
文献类型：
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作者：
Fumihiro Hanasaka;and Ken-ichi Fujita;R. Yamaguchi
为了提高[Cp*IrCl(μ-Cl)]2的催化活性，合成了几种新型阳离子Cp*Ir N-杂环配合物，并研究了它们在Oppenauer型氧化中的催化活性。 [Cp*IrCl(μ-Cl)]2 (1) 与 N-杂环卡宾配体的反应得到 Cp*Ir(L)Cl2 (3a−d; L = N-杂环卡宾配体)。阳离子配合物 [Cp*Ir(L)(MeCN)2]2+ (5a−d) 是通过用 2 当量的 AgOTf 处理 3a−d，然后添加 CH3CN 获得的。配合物 3a−d 和 5a−d 的结构通过 X 射线晶体学研究确定。配合物 5a（L = 1,3,4,5-四甲基咪唑-2-亚基）在温和条件下非常选择性地催化伯醇和仲醇的 Oppenauer 型氧化。以5a为催化剂氧化1-苯基乙醇和环戊醇，转化数分别达到3200和6640。这些结果表明，据我们所知，阳离子卡宾配合物 5a 是最有效的催化剂...
Several new cationic Cp*Ir N-heterocyclic complexes have been synthesized and their catalytic activities in the Oppenauer-type oxidation have been investigated in order to improve the catalytic activity of [Cp*IrCl(μ-Cl)]2. The reactions of [Cp*IrCl(μ-Cl)]2 (1) with N-heterocyclic carbene ligands afforded Cp*Ir(L)Cl2 (3a−d; L = N-heterocyclic carbene ligands). The cationic complexes [Cp*Ir(L)(MeCN)2]2+ (5a−d) were obtained by the treatment of 3a−d with 2 equiv of AgOTf followed by addition of CH3CN. Structures of complexes 3a−d and 5a−d were determined by X-ray crystallographic studies. Complex 5a (L = 1,3,4,5-tetramethylimidazol-2-ylidene) catalyzed the Oppenauer-type oxidation of primary and secondary alcohols very selectively under mild conditions. In the oxidation of 1-phenylethanol and cyclopentanol using 5a as a catalyst, turnover numbers reached 3200 and 6640, respectively. These results demonstrate that, to the best of our knowledge, the cationic carbene complex 5a is the most effective catalyst i...